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OZ951 ( aka OZ996 ) (aka Kelly Anne) Porsche 996 Page

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"Emmy" 996 Carrera 3.4L 6spd

Last Updated 2 Feb 2014 

Warning 996's are highly addictive - leave this page now for your own good.





Currently living in ->


Aero kit    Accusump

Brakes   Battery

Cooling    Cup Steering Wheel


Engine    Exhaust

Hood & catch

Intake / CAI   LSD

Oxygen sensors  OEM vs Original

Reversing Light    Roll Bar

Suspension  Splitter  Sunroof

Transmission  LSD Tyres

Wideband 02  Wheels


Useful Links


My channel on


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Originally I added new information at the bottom of the page and it was in chronological order with the original/oldest information closer to the top. However over the course of time I have updated many of the things I have done with the car so the latest information could be anywhere within the page. With that in mind I have created the contents list above and to the left  and that will take you to the key areas of the page based on a given functional area like the workshop manual. I also maintain 3 links (upper left corner of this page) to the latest 3 things I have been doing with the car so that is the fastest way to find what I have been doing with the car. These pages are not sponsored by anyone other than me and the links on the page are there either for my own benefit or to aid others in finding out more information about the associated kit.

I'm an Aussie and I've lived in the US & UK for a few years respectively I started with 944 Turbos (951s) in 2001 whilst I lived in Texas USA. I purchased an 02 C2 Tip in late 2009 whilst we lived in the UK but didn't really delve into the 996 properly until Sep 2010 when I replaced the 02 Tiptronic to buy the 99 C2 6Spd to which this page is dedicated. I didn't originally plan to build it into a track car but that is the way it evolved. It is now 2014 and we live in Sydney Australia. Hopefully these pages will give fellow 996 enthusiasts some insights and perhaps some inspiration. These cars have their share of issues but in my experience all Porsches do, so it's worth dealing with the issues and then enjoying the car for what it is.

Out for a drive into the Blue mountains (NSW Australia) Jan 2014.


Sep 2010. As we come to the end of our first year in the UK we have purchased a 99 Porsche 996 Carrera 2 (ie 2WD). This is actually an older car than the black 996 C2 Tiptronic (2002) we purchased when we first arrived. After some shopping around we had some good fortune in spotting this ad within 30 minutes of it going online and 3 hours later it was ours (and that included a 2hr drive to get there!). This car which we named Emmy was well cared for by its 3 previous owners and had low mileage (68K) with good service history. It had a partial GT3 body kit (bumper & side skirts but no rear spats and a cabriolet rear spoiler...) and Sport Classic II wheels, unfortunately the wheels were the let down and were quite unsightly and I have since had them refurbished.

Part of the reason for going for an early model was that doing so provides a budget for adding the kind of options and modifications that suit our requirements. Primary among those is the need to address an uncommon but potentially catastrophic failure that can occur with the M96 engine in the Porsche 996 and 997. More on that later. So the rest of the budget is to get the car performing and sounding it's best and finishing off the body kit in a functional way that will not hamper the cars handling at track speeds. The rest of this page will detail the modifications and experiences and hopefully lots of Porsche 996 DIY efforts and upgrades as I get the car into the condition I'm after.

Goals. As I have a Porsche 944 Turbo  (951) track car in Australia (See Link). The plan is to get in a few track days in the UK but when we leave the UK this car will be heading back to Australia with us as a long term daily/weekend driver. Hopefully this 99 Porsche 996 C2 will have a future in Australia.


Original  Spec

Engine 3.4L 6 Cyl M96 engine develops 296 BHP and 260 ft/lbs at the crank (M5.2.2 ECU)

Top speed 280 kmh, 0-100 5.2 Sec

Transmission G96 6 Spd  manual with option 220 LSD (G96.00.2.xxxxxxx) - Option 220 is relatively rare, it's a 22/40 LSD with no PSM. My LSD is upgraded with GT parts to a 40/60 setup with GT Friction plates & pre-load.

Wheels 7.5J ET50 plus 15mm spacer  10J ET65  (Tyre Calculator Link) (Ratings Z=150+mph, W=168mph, Y=186mph)

Tyres as of May 2011: Michelin Pilot Sport II - N3. 225/40ZR18 & 285/35ZR18 (Jul 2012 from 265)

Brakes Front 318x28mm cross drilled (directional) 4 Piston Brembo Std. Rear 299x24mm cross drilled (unidirectional) Brembo 4 Piston Std.

Weight 1430kg with full tank (64L / 47.2kg) fuel, bodykit, Sport classic IIs, spare & tools etc. As weighed 9 Oct 2010.


Current Track Spec

Engine 3.4L 6 Cyl M96 engine develops 311 BHP and 260 ft/lbs at the crank (M5.2.2 ECU)

Transmission G96 6 Spd  manual,  LSD upgraded with GT parts to a 40/60 setup with GT Friction plates & pre-load.

Wheels Front 8.5J ET45 plus 7mm spacer, Rear 10J ET65, Team Dynamics Pro Race II

Tyres: Michelin Pilot Sport Cup 235/40R18 & 295/30R18

Suspension Intrax 1K2 Single adjustable 570F/1254R (in/lbs) GT3 F&R ARB, Monoball coffin arms and top mounts, RSS Toe arms, billet caster pucks.

Brakes Front 350x34mm Dimpled PF 2 Piece rotors with Porsche 6 piston calipers. Rear 330x28mm cross drilled OE discs. GT3 master Cylinder and Vacuum booster. GT3 Cooling ducts Front, GT2 cooling ducts rear. Castrol SRF.

Weight 1312kg with 1/2 Tank as corner balanced Jan 2012.



An early morning photo op prior to doing some brake testing.

Latest high resolution pic

Jul 2012 Porsche day at Donington Park


Hunter Valley winery tour with PCNSW 2013t

First steps - Porsche 996 Dyno Baseline (1 Oct  2010)

Since the early M96 engine is a 3.4L version rated at 296 Hp rather than the 3.6L 320Hp engine in the 2002+ cars it was worth doing some improvements to intake and exhaust in order to get some performance gains and to get a decent exhaust note. Porsches PSE exhaust sounds great but Emmy was only fitted with a standard exhaust and it really masks the lovely sound of the 911 engine. The exhaust will be tackled in 3 parts, headers, catalytic converters and mufflers. There is always much conjecture about the performance gains from such components and I decided that I would make several trips to a reputable dyno in order to measure the performance impact of each separate component.

So the first dyno trip to Corten Miller in Lincolnshire was aimed at measuring the baseline power and torque at the wheels for the completely stock car. Several runs were performed on a dyno Dynamics dyno in shootout mode which is a standardised mode which takes into account the conditions during the test so that the results can be compared to subsequent days results even though the temperature and humidity etc may be different. The wheel horsepower was measured at 236.4 Hp which indicates a roughly 20% loss of power through the transmission.

The next step was to fit a cold air intake (CAI) which provides a less restrictive air flow. I elected to fit the CAI in a bit of a hurry while the car was still on the dyno. During a test fit of the  CAI I had noted some fitment issues that would take a bit of time to sort out so whilst the car was on the dyno I fitted the air intake and filter but not the associated heat shields. When we ran the dyno we noticed a couple of things.

a) the intake air temp was higher (65c rather than 45c) due to the heat shields not being fitted and thus allowing the intake to draw in warmer air.

b) the Air Fuel Ratio (AFR) with the CAI fitted was considerably leaner than with the stock intake fitted. This may be attributable to several things including the differing air flow characteristics in the CAI large diameter intake, the warmer air and the fact that the ECU may need to 'learn' the different characteristics before it can compensate the AFR appropriately. Whatever the reason, the AFR was a bit leaner than I am comfortable with for driving under power (such as at the track) and more work will have to go into understanding the cause and optimising the setup with the CAI installed. Ideally the AFR will be in the order of 13-13.3. Despite the less than ideal conditions the CAI did manage to deliver an extra 5Hp, so with some improvements it may do better still. One thing that supports that conclusion is that the graph shows a sudden drop in power as the AFR leans rapidly, hence if the AFR can be optimised the power should improve likewise.


Stock Dyno - 1 Oct 2010

Stock plus CAI 1 Oct 2010

8 Oct 2010: Data acquisition:


Note this dyno run  was with 95 octane regular unleaded in the UK. The M96 is tuned for 98 Octane gas hence some ignition retard is likely to have occurred and had an effect on the results. I'll quantify this later on by repeating the tests with some 97/99 octane BP ultimate or Shell Vpower after a suitable period of ECU adaptation. Two other key notes with this graph are that it was 95 RON (M+R)/2 gas and that the AFR measurement was with a post catalytic converter WB02 hence the measured AFR will have been influenced by the effect of the catalytic converter (ie the displayed AFR is leaner than the true AFR).  

Baseline Dyno run



25 Feb 2011  2nd Set of dyno runs (RWHP)

I have the Fabspeed muffler on the car at the moment along with the Fabspeed 200Cell X Cats and the cheap but well made headers from Ebay. The car is running with a new K&N panel filter in the stock air box (I sold  the Fabspeed carbon fibre competition CAI as I did not like it - at all).

This run was conducted with 97 RON BP Ultimate vice 95 RON Jet.

The dyno dynamics shoot out mode would compensate for atmospheric variations between the original run and todays run but as it happened there was only 1 degree difference in outside air temperature anyway.

At the upper end of the graph there appears to be about a 10 Hp improvement but the real improvement is in the lower RPM range where there is a healthy improvement in torque and Hp across the range. Increases top out at about +26Ft/lbs of torque and +20 Hp.

After this run the main question I still have is  whether the Ebay headers have made an improvement over the OEM headers or not. So I'll have to get back to the dyno again some time with the old headers on and find out.



Click on chart to see bigger version

Click on chart to see bigger version

Video clip of dyno run (right click & save as)

The chart below is a run at the track on 97 RON with the car in the same configuration as it was for the dyno. Timing is pretty steady and AFR under load is also pretty consistent.


The chart below is a data acquisition performed during one of the Feb 2011 dyno runs. The main piece of information I am interested in from the chart is the timing data under load.


Apr 2011 Dyno - Header comparison results

Today I took the car back to the dyno after re-installing the OEM headers last weekend. The sole purpose of this trip to he dyno was to establish whether the aftermarket ebay type headers are better or worse than the OEM headers in terms of performance.






Baseline (Oct 2010 236.4 Hp) vs latest (Apr 2011 253.6Hp) dyno

Timing / RWHP / FWHP / AFR

The charts above show the data logged during this dyno run and the dyno chart itself is a comparison between the original baseline dyno run I did in Oct 2010 and todays run. The chart lists the configuration. The key things I am monitoring with the data logs are the ignition timing (influenced by the fuel octane rating) and the AFR. The last two charts above are the same run with Crankshaft/Flywheel HP (S_Hp) displayed and the AFRs measured during the runs with ebay vs OEM headers.


OEM vs Ebay headers

This is a pure header comparison run. The bottom line is that the aftermarket headers rob about 10Hp across the board. They are well made and the OEM headers look agricultural by comparison but rough looks aside the OEM header is a better performance design.


August 2011 Dyno - Pre ECU Flash baseline

Next week I will be taking the car to Chipwizards to get the ECU re-mapped. Before doing so I was keen to get a new dyno baseline in the same configuration that the car will be re-flashed with. The following things changed between this run and the last run I did in April:

Fuel - went from BP 97 to Shell 99 Octane

Cooling - added low temp thermostat & 3rd radiator.

Spark plugs - Installed fresh Bosch plugs vs old NGK plugs

Tyres - New Michelin PS2s vs old & worn Contis


Results August 2011

Dyno run 030 August vs April (Run 019)

Data log captured during dyno run.


This dyno run was 13 RWHp less than the previous best run in April. This was a bit of a surprise at first since the car was running cooler (80 degrees C vs 88 degrees) and was using fresh plugs of the correct heat range and higher octane fuel.

Actual Baro pressure, humidity, air & intake temps can be read off the respective charts but they are pretty similar and corrected for in dyno dynamics shoot_out mode anyway. From the data log it can be seen that slightly retarded timing was used in this run (21deg) compared with the previous best run (22deg), despite the higher octane fuel being available. At this stage I'm not sure if that is attributable to the cooler temperature or perhaps a result of  ECU 'learned data'. A 10 minute battery disconnect had been performed at the dyno to reset the ECU but it didn't make any difference to the results. 

The 13 Hp recorded loss is attributed to the tyres - with the newer, softer, gripper tyres with larger tread blocks deforming more (& absorbing more power in doing so) on the dyno rollers.

Here is a very good example of how tyres affect the readings   See full article here.  WRX RE-01r & Blizzak WS-70 tyre comparison. The other pic is shows an example of tyre deformation on dyno rollers and helps to understand how a certain amount of energy is absorbed by the the tyre (think of how much effort you would have to put in to deform a tyre that much) and that is related to the tyre construction, sidewall stiffness etc.

ECU Remap / Dyno - August 2011

I took the car to Chipwizards near Manchester to have it re-mapped by Wayne Schofield. Wayne previously raced 3.4L 996 Carrera so he is pretty familiar with what the motor can and can't deliver both from a tuning perspective and also from a reliability perspective in terms of track endurance.

Right from the get go he pointed out that the 996 Carreras tuning was pretty good and that there wasn't going to be huge gains. Only expect about 8Hp or so were his pre mapping words. That was honestly lower than what I wanted to hear but if a guy who raced these cars and tunes them for a living was only getting an extra 8 HP from his race car then so be it.



Wayne uses a Bosch dyno with an in built weather station which corrects for atmospherics and uses the coastdown to establish the transmission losses on each run. As it turned out the initial dyno runs (pre mapping) were actually very similar to the runs I had on the dyno dynamics dyno both in RWHP and S Hp. After a few technical hitches with my ECU not wanting to accept a new map write, some progress was made. The chart below shows the end result - the upper pair of lines being the S Hp and the lower set being the W Hp. As can be seen the peak number really isn't that much higher at all. Despite the peak number not looking much improved, modest gains can be seen in the 120-170mph bracket of the chart, equating to about 5750 rpm and above. That should be worthwhile on the track. The middle portion of the curve shows about 10Hp improvement tapering off as rpms drop. That being the case I didn't really expect to feel much improvement down low at all. Well I was completely wrong there - driving home it became clear that the car was feeling more responsive to throttle inputs and more willing to get going. I was pretty surprised by this and was kicking myself for not asking Wayne for a torque vs Hp printout - I had assumed there would be no change there. I know Wayne richened up the mixtures a bit and when I got home I checked my tail pipes and sure enough there is definitely a blacker shade to the tips - I specifically noted this because I had been observing it closely recently (& photographed them) and my exhaust tips (& plugs) had always indicated a tan (lean) fuel mixture with no hint of black. So I am sure it has been richened up down low and this has had the effect of increasing torque - now I'll have to take it back to the dyno dynamics dyno and run it again so I can get what has become my standard dyno chart for comparing Hp/torque and Air-Fuel Ratio (AFR).  The other two charts are data logs I have collected since the dyno runs - primarily to have a look at the AFR and timing.


Porsche 996 Spark Plugs

In the course of checking the dyno results I obtained in August I had cause to verify the suitability of the spark plugs I was using. Between Oct 2010 and August 2011 I had been using the NGK BKR-6EQUP as was fitted to the car when we purchased it. In preparation for the ECU re-map I put in fresh plugs. I ordered Bosch FGR-6KQC plugs (copper core) but what was delivered was FGR-6KQE plugs (Nickel Yittrium core) these are both surface firing 4 electrode plugs. The KQE is just a later revision of the plug. It's worth noting that Porsche has changed the recommended plug type several times over the life of the 996. When ordering plugs from Porsche it is likely that the part in the box will be a Beru plug 14FGR-6KQU. The afore mentioned Bosch and NGK plugs are equivalents. There are several other plugs that are considered to be interchangeable with the plugs I have just listed but they may be of an older / more conventional style. The surface firing plugs are supposed to create a longer spark which flows over the insulator to result in a more effective burn with lower emissions.

Click on the thumbnail for a chart which you can use to decode the meaning of BOSCH plugs.

F = M14x1.25

G = Surface Gap plug

R = suppression resistor

6 = middle heat range

K = thread details

Q = 4 electrode

E = Nickel Yittrium

Beru plug 14FGR-6KQU


Bosch FGR-6KQE


Wide Band O2 - 24 Oct 2010   Back to top of page

As part of the process of tuning/re-mapping the car I need to monitor the air-fuel mixtures using a wideband O2 sensor because the Oxygen sensors fitted as standard are not suitable for the task. I chose the Innovative Motorsports LC-1 as the wideband system, and it is coupled to a laptop or OT-2 for monitoring AFR / data logging.


The WB02 sensor itself is mounted to one of the four O2 sensor bungs that are on my fabspeed cats so I didn't need to weld on an extra bung (unless I want it upstream of the cat - normally I would, more on that later). The electronics module I positioned as per the attached pic. The earth point I used is a stud for mounting the coolant tank. There is an M6 bolt hole a few inches away which I will use when I get a suitable M6 short bolt.

I took power from the plug as can be seen in the pic - however - it is a constant 12V source, rather than an ignition 12V source so I still had to install a relay to trigger via an 12V ignition source and connect to this power source. (otherwise the WBO2 would be on continuously and drain the battery). The wiring was then run along the same path as the factory wiring and along the back of the engine bay to the LC-1 electronics module.

The LC-1 sends the AFR signal out via a serial cable with a 2.5mm socket and this needs to be brought into the cabin. A quick check around on Rennlist and I learned about a suitable access point on the rear shelf. To get to it I had to remove the cover behind the rear seats (just pulls out), then undo the 6 bolts that secure the ECU and relay board, this allows the rear deck padding to be lifted up and access the rubber access grommet. I pulled out the trim piece and padding that cover the rear wiper motor - but you may be able to avoid doing so. Puncture the grommet with a stubby pointed implement and then push through a wire coat hanger to use as a pull-through.


The new Fabspeed X cats were nice and easy to undo but one muffler needs to be removed as well in order to make enough space to get the X cats out. I took the cats out so that I had adequate room to install the old and new O2 sensors.

The LC-1 does not ship with a 2.5mm to 2.5mm serial cable of the type needed to connect to an OT-2, so order the accessory cable with the kit (or head to Maplins and make one).

Here you can see the other end of the pull through and the end of the serial cable which needs to go into the cabin. Tape the socket to the pull through and then draw it into the cabin.

Since the serial cable socket is thicker than your average wire I pulled the grommet out and and sliced it as per the pic and then re-installed it.

Everything back in place. From here the cable can be routed a variety of ways that don't require any trim to me removed. I ran it along the edge of the wheel arch trim and the connecting cable runs under the floor-mat and front seat.

Here is one of the first logs taken with the WBO2 installed. The green line is the flat line responses from the dead stock O2 sensor (0.435v). The red trace is the good stock O2 sensor and the purple line is the WB02 Sensor. Note as the purple wideband AFR line goes north (lean) the red narrowband goes south (also lean) because of the voltage response of the narrow band sensor. ie the red line is indicating rich when it's near the top of the graph and lean when it's near the bottom of the graph. The data response from the WBO2 sensor is very fast direct serial output, but the narrow band O2 signal from the OBDII port is at a lower response rate so it seems more 'steppy'.    

95 RON Fuel vs 97 RON Fuel

The following two logs are wide open throttle runs to observe the AFR and timing advance under load. One was conducted with 95RON fuel and the other with 98RON fuel. The logs sow that with 95RON fuel the ECU starts with about 22-23 degrees of timing and then retards the timing back to 18-19 degrees as the load increases. When doing similar runs with 97RON fuel the timing starts around 23 degrees and pretty much maintains that timing throughout the runs. 95 RON 97 RON


As mentioned the Porsche Sports Exhaust (PSE) sounds great (I have been driving it around for the last year on our other 996) but Emmy's exhaust is stock and sounds pretty timid by comparison. Unfortunately PSE is very  expensive and whilst it sounds good, it doesn't make any significant contribution to increased power. Hence the logical way forward is to buy an exhaust that is free flowing and sounds good... but it must not have that dreaded resonance that many exhausts have. So I have purchased a Fabspeed system which is renowned for sounding aggressive yet free of annoying resonance's. The Fabspeed mufflers are also free flowing and I have purchased 200 cell Fabspeed catalytic converters in a scavenging X formation to go with the mufflers. This will save some weight and hopefully a few extra HP as well as a decent exhaust note. One area I went cheap on is the headers - the factory headers look pretty crude but are supposed to be of a reasonable design despite the pretty rough internals. I purchased some ebay headers because they (like the SSK) actually look very well made and very cleanly finished internally. The ebay headers cost 1/6th the cost of most aftermarket headers so naturally everyone thinks they must be rubbish. They may well be but finding the answer to that question is probably the main reason I decided to baseline dyno the car to begin with. Once the headers are installed I will dyno the car again and see how the performance has changed. If there is zero HP improvement I will be happy as the headers are stainless steel, light and will resist corrosion a lot better than the stock ones. If the ebay headers actually rob some performance then they will be making their way to the rubbish bin.


Weight wise the Fabspeed system is measuring up as follows

Fabspeed Cats (as a single joined unit) 6.6 kg (Stock...10.6kg per pair)

Fabspeed Mufflers 6.3 kg each side (Stock ....9.6kg each side)

Ebay Headers 3.7 Kg each side  (Stock .... 3kg each side)

Exhaust Install (Cats & Muffler only)- 16-17 Oct 2010  Back to top of page


The mufflers clamp to a mounting bracket with a 70mm and a 140mm bolts oriented vertically. Leave these alone until the muffler is off the car as there is not enough room to remove these bolts while the muffler is mounted.

The mounting bracket has 3 studs and is attached to another bracket using 3 nuts. These are the three nuts (13mm) that have to be undone to remove the muffler from the car.

There is a sleeve that connects the muffler pipe to the cat pipe. The two 17mm nuts on the sleeve have to be loosened so that the sleeve can be slid out of the way to allow muffler removal.

The cats have 3 studs which are secured to the header flange using three 13mm nuts. There is also a band clamp that secures the cat to a mounting bracket. This clamp has to be loosened in order to remove the cat.

Prior to removing the cat(s) unplug the oxygen sensors in the engine bay area. The oxygen sensor plugs are locked together by a dark red piece of plastic (Link). The red piece of plastic must be pulled to the open position before the oxygen sensor can be

Tips on 996 oxygen sensor connections.

Fabspeed system ready to be installed

Sock header bolts look nasty so this job is being saved for the workshop.

These bolts look bad as well but cutting tools can be used here as I will replace these parts.


Even though I used PB blaster to try and free up the bolts, these ones snapped straight away. Incidentally these bolts are not the ones that need to be undone to get the muffler out of the car - as there is no room above the bolt to remove it even if the nut comes off.

This is the worst corrosion I have seen - it doesn't even look like there was a nut there (there was originally)

This is how the bolts were dealt with.

A 100mm angle grinder with a metal cutting disk makes short work of the sleeves (just cut the bands on the sleeves, you don't need to do the bolts).

The angle grinder will also readily get to 2 of the three studs/nuts that protrude from the cat through the header flange.

If you intend to re-use your cats you'll need to press/drill out the studs.

These are the three nuts that must be undone to remove the muffler. This view is from the middle of the car looking towards the side (through the header).

It's also vital to get these nuts off carefully because you cant get to them with a cutting tool if you strip them. So soak them in PB/blaster or liquid wrench for several minutes, brush off any loose rust / muck off the threads and make sure the socket is properly seated and square on to the nut. Proceed slowly and soak the nuts/threads again after the nut has started to turn. Screw this part up and you will regret it.

A socket driver will reach all three bolts. The base of the socket driver is pointing at the rear of the rear tyre.


I have seen another guide which suggests using a universal joint and socket extension bar (pic) to undo these nuts. However I find that universal joints tend to bind a bit and don't give a good feel for how the nut is loosening up and it's important to feel that if you dealing with a corroded nut/bolt.

Two of the header-cat flange nuts were cut off using an angle grinder but this is what I had to use to cut off the third one. The car has to be high enough to make space for the tool underneath the car. I did this with the car jacked from one side only. The tool only just fit between the floor and the problem stud -  tight but do-able.

The muffler can come out with the bumper in place. Move it towards the side of the car until it disengages from the mounting plate then rotate the tip downwards and push the muffler back towards the tyre - it came out pretty easily - even with this side of the car being on the ground (not jacked).

The muffler tips looked pretty ordinary to begin with.

And I was pleasantly surprised to find t hat 5 minutes with a rag and some metal polish produced a good finish.

Another 5 minutes with a clean rage and some more polish produced this. Job done. I used Auto Glym metal polish.

Muffler with old tip and old muffler bracket installed.

I started the install by loosely bolting up one side of the cat to the header flange.

This pic shows that there was only a minor misalignment between the cats and stock header

A close up of the gap, this was pulled in without any excessive force using the new stainless steel bolts I purchased for the job.

Going back a step this pic shows the muffler bracket with a sleeve running  through the centre of the wire mesh. The sleeve in the wire mesh is a new one I made from some 12mmx1mm steel tube as the original bolt had broken off in the original sleeve and the sleeve had started to crack so I chose to replace it.

The stainless bolts I purchased for the job were socket head stainless bolts rather than hex head. There is not much clearance between the bolt head and the frame of the car when the muffler is in place so I used a shortened allen key to counter-hold this bolt whilst I tightened the nut from below. Whilst I could have tightened these bolts before fitting the muffler in the car I elected to do them after the muffler bracket bolts were done and after the cat-muffler sleeve was tightened as this method allows better / easier alignment of the muffler.


This is the shortened allen key I used on the muffler bolts once the muffler was mounted and connected to the cats.

This shows the minor gap between the muffler and the cat section before sliding the sleeve into place. This pic also shows the positioning of the muffler tip clamp/bolt. This position for the clamp wasn't ideal but I did manage to get it suitably tight with a gear wrench.

Sleeve secured over muffler/cat pipes.

Partial install view

Partial install close up


The muffler tip clamp should be snugged up but not clamped tight before installing the muffler - then the muffler tip can be adjusted for an even gap with respect to the rear bumper skin.

Alternate view of muffler tip gap.

Job done.


20 Oct - Whilst this job was in progress I was unable to loosen the O2 sensors from the cats since I am without air tools here in the UK. My 22mm spanner was looking ready to break and the O2 sensor wasn't budging so I ordered a special O2 socket which has a slot for the cable. This one is made by Lisle and looks well made like an impact socket - although it was only a 3/8 drive. Today the socket arrived and I started with a 1/2" drive adapter and my usual breaker bar but still the O2 sensor wasn't moving. So I resorted to using half of the handle of my trolley jack as extra leverage. Both of the O2 sensors gave up at that point and separated from the cats. As you can see from the pics the sensors look well worn but they are perfectly serviceable (as I have established from my O2 data logging over the past few weeks)

  Notes: Originally I didn't manage to get the oxygen sensors undone from the old cats so I installed the cats without O2 sensors. I expected to get a Check Engine Light but that didn't  happen (surprisingly). Diagnostic / Error Codes

My car is a 99 UK car so it only has 2 oxygen sensors, pre-cat of course.

22 Oct 2010 - Header Install

Given the state of the header bolts I expected there would be problems so I took the car into Gantspeed, they are a company that specialises in restoration work and with that in mind I figured they would be well placed to deal with these corroded bolts. In the end 8 of the 12 bolts sheared and required drilling out. Time-cert thread repairs were installed for those 8. Socket head bolts were used rather than hex head bolts for clearance reasons but other than that there were no other fitment issues. I had previously checked the bolt hole positions by putting fabspeed copper gaskets on the ebay headers and the bolt holes lined up perfectly. I also had the guys at Gantspeed replace the 4 bolts (2 each side) of the tubular muffler brackets since those bolts were equally as bad and I intend to replace those brackets when I pull the engine. Total time was 9.75hrs labour. Not cheap but at least the worst bolts on the car have now been dealt with.


Before and after shots


So, now that these are on I can carry on with the dyno plan. Next dyno measurements will be done on Tuesday.

Catalytic converter

Stud Removal

23 Oct 2010

As I had to cut the studs to remove the cats I now had to remove the studs  from the cats entirely so that I can use regular bolts to mount the stock cats when needed.

The approach I used was to start by cutting the studs flush with the flange using an angle grinder and cutting wheel.

I then drilled a 2.5mm pilot hole all the way through, followed by a 6mm hole about 90% of the way through. I let the parts cool and applied some penetrating oil, then I braced the flange against some timber and hammered out the stud with a punch.

When cutting the studs, avoid cutting the sealing edge near the round mouth of the flange, so cut from outside towards the mouth and keep the angle of the cutting disk fairly parallel to the flange surface so that you don't grind into it too much.

The cats looked like they are in excellent shape with no signs of melted material causing blockage. Certainly nothing like my 951 cat looked like a few years ago.

Driving Impressions. Nov 2010   Back to top of page

I have waited a while before posting my driving impressions so that I could drive the car under varying conditions and hear what it sounds like. My first impression was that the exhaust was quieter than I expected - this is with stock & ebay headers and with X cats fitted. The sound is quite different from PSE, PSE is throaty whereas the Maxflows have a more muted sound to them. They are definitely more aggressive than stock and it is much easier to hear the engine note for shifting etc it's just different to PSE. Under wide open throttle the maxflows do sound good. However in my car they do drone when the revs are in the 2500-2900 rpm range. I found that for short trips I would rev harder and change gear more often or leave it in a lower gear to keep the revs up. This does reduce the drone but it is an impractical way of driving especially on long trips in traffic. My wife wasn't overly happy with the drone and after doing a road trip with my brother I concluded that the mufflers were taking the pleasure out of driving the car and I removed them.

Fabspeed Follow up Dec 2010

Despite the drone issue I noted, I'm not finished with these mufflers yet. It seems to be the case that some cars experience the drone with these mufflers and some don't - there is also some opinion that the drone reduces with time (I don't know how that works). Since the mufflers do offer the benefit of reduced weight I'm keen to experiment a bit and see if the drone can be eliminated. I'm going to re-mount them with different hardware and run the mufflers at the track and see if that hard running has any effect on the situation.

Follow up 2011: I have re-fitted the fabspeeds despite the drone because they do perform better than the OEM mufflers. Here are some clips of the exhaust note whilst at the track.

Clip 1   (Save Link as...)

Clip 2

Clip 3


Ebay Header Follow up 2011

Now that I have had a chance to dyno these headers it is clear that they rob about 10 Hp. See dyno charts above for the details.

Porsche 996 Exhaust Modification (PSE Hack/Fister mod) 23 Dec 2010

As I was not happy with the drone from the Fabspeeds I decided to go ahead with the PSE hack/fister mod on my standard mufflers. PSE hack refers to a modification which resembles the basic element of the Porsche Sports Exhaust (PSE). In the PSE part of the muffler is bypassed when a valve opens. The PSE hack simply involves cutting a hole in the inlet and outlet pipes of the muffler and welding a stainless steel tube between those holes. The tube is of a smaller diameter than the main pipes and thus only some exhaust gas travels via this bypass route. The result is an improved tone & loudness level which many 996 owners consider to be sporty in comparison to the stock mufflers which many 996 owners consider to be too subdued. By comparison the elimination of the mufflers by the use of 100% bypass pipes is almost universally considered as unacceptably loud.

I had the modification performed at a local engineering company that specialises in metal fabrication and welding. I took the mufflers in with some pics of what I was after and I gave them a section of 180 degree U shaped 1.5" stainless steel tube (ebay £13). They charged £177 and did an excellent quality job. There are quite a few variations on where the tube can be welded to and from and from what I have read they all seem to deliver about the same effect. Presumably the diameter of the connecting tube will govern the loudness of the result. From my research 1.25" tube seemed pretty popular although I have read of tube sizes between 1"-2" being used.

This modification is not believed to offer any performance benefits, just an improved exhaust note. The two pics to the left show the two factory variations of PSE. The first pic is the PSE version one as employed on 996.1 3.4L cars and the other pic is PSE version 2 as applied to 996.2 3.6L cars. My understanding is that the internal baffles for the 996.1 and 996.2 mufflers are different but I haven't seen it for myself.


My modified exhausts PSE 1 style - 1.5" Bypass. These (unmodified) mufflers were fitted to my car when I purchased it, others who have seen the pics believe them to be 996.2 mufflers because of the bellows and shape of the upper sealed exhaust port. I could find no record of an exhaust change in the cars history but it may have been undocumented.


 Now that I have driven the car around for a while I can provide some feedback on how these sound and to put these comments in perspective I am making them after owning a stock 996.1, 996.2 with PSE2, and 996.1 with Fabspeed Maxflow mufflers.

They make a nice little bark on startup.

The Idle and part throttle noise is basically the same as stock.

There is no drone.

The aggressive throttle and wide open throttle noise is sporty loud, loud enough to hear what the motor is doing for heel and toe shifting, loud enough to hear with the windows up but not so loud as to be intrusive. This is pretty much ideal in my view.

By comparison I found the fabspeeds to be not really loud enough under higher throttle inputs but they did still sound nice and different, the issue for me with fabspeeds was an intolerable drone between about 2400-2900 RPM.

Click on  picture or right click and Save As or Save link as...(12Mb file)


Coolant leak 24 Oct 2010


After a short drive yesterday I noticed the low coolant lamp flash. I wasn't entirely surprised as the coolant had been drained a bled a few days before to do the headers and I figured some air had worked it's way out of the system and the coolant level had dropped. accordingly. However when I got home and checked the coolant level I could smell coolant in the engine bay and on looking closer I found that the expansion tank had in fact begun to leak. The cap is also an old style cap so replacements have been ordered for both. At this time I am liking the fact that it's an early 996 and I wont have to lower the engine to get the coolant tank out.

In - car Renntech DIY for pre-face lift cars.




Oxygen Sensors 25 Oct 2010    Back to top of page

After my Oxygen sensors went in & out of the car during the exhaust removal I noticed (from my data logging) that the signal from one of the sensors was flat lining around 0.45V. That would have been ok for a post cat sensor but not good for a pre cat sensor which should be oscillating between 0.1 and 0.9V ish.

So I set about looking for a replacement sensors. Past experience tells me the dealer charges a significant mark up for a direct fit replacement. The direct fit replacements are a standard bosch sensor with a cable length and plug type to suit the vehicle in question. The alternative is to buy a Bosch universal sensor and splice on the old plug & cable. Generally a much cheaper option and Bosch provides a splicing kit which preserves all the necessary characteristics of the installation such as free air reference.

pre-facelift & T/GT models use the thimble style (right)

Post facelift models use planar sensors (left)

996 3.4

The bosch part number  pre cat (control) is 0 258 003 564

The bosch part number  post cat (diagnosis) is 0 258 003 723

The bosch universal part number for both is 0 258 003 505


For my application the Bosch universal sensor will suit, it is Bosch part number 0 258 003 505, also refered to as LS05. These are 4 wire thimble style sensors. These work for 993, GT-2, GT-3, 996T. The planar universal sensors suit the 3.6 M96 series engines.

0 258 003 564

996T GT-3 GT-2

The bosch part number  pre cat (control) is 0 258 003 721

The bosch universal part number  is 0 258 003 505

So with this information I went shopping for a replacement sensor. In the UK I found an online O2 sensor specialist "Just Lambda" which had good prices for my direct fit (£72) and universal sensors (£49). Given the relatively small price delta I have ordered the direct fit part (0 258 003 564) 28 Oct - this was delivered & all good.

Wire Colour coding

White - Heater

White - Heater

Black - Sensor signal output

Grey - integrated earth reference

996 3.6

The bosch part number  pre cat (control) is 0 258 006 564

The bosch part number  post cat (diagnosis) is 0 258 006 433

The bosch universal part number for both 3.6 is 0 258 003 602


Engine / IMS  - Dec 2010

The M96 engine has a design flaw that affects the 996, 997 & boxsters. The flaw affects develops in a relatively low number of cars and is related to the Intermediate shaft (IMS) bearing. The bearing is sealed and for whatever reason (a subject of much debate) the bearing deteriorates and fails. When it does fail it goes from being all is well to destroyed engine in a matter of seconds with little to no audible warning. This has happened to cars with all sorts of mileages including less than 20K on the Odo and yet others have gone 120K without failure. That's all a bit too random for me and being a worry wart I don't really want to deal with that on a continuous basis. The solution (nobody knows if it's a final solution though) is to go with an IMS bearing replacement kit. Porsche has re-designed the IMS several times but continues to deny there is an issue. I ordered a LN_Engineering  replacement IMS bearing kit as this seems to be the one that is working for the majority of the 996 customer base in the US. Other options exist here in the UK through Hartech although I am not familiar with the Hartech solution myself. This isn't a trivial task as the transmission will have to come out of the car in order to get to the IMS bearing but once in that area it's a good time to replace clutch, rear main seal (for crank) and flywheel. Now that the weather in the UK has gotten icy I have taken the car off the road to undertake this job and several others. Given that there is a fair bit involved I have dedicated a web page to the engine removal / IMS replacement and associated jobs.

Relevant Links

LN Engineering IMS kit pdf

Flat 6 Innovations

Porsche Manuals & PET parts program

C-Speed RMS / Trans removal

6Speedonline transmission removal (Doc Wilen)

Engine drop DIY 1 (Rennlist)

Engine drop DIY 2 (Rennlist)


Engine Oil selection



Link to my engine drop DIY page

M96 (Boxster and 996) Engine Issues

UK IMS options

Here in the UK a well known engineering firm by the name of Hartech has established itself as an industry leader with respect to analysis and repair of the M96 and M97 engines used in Boxsters, 996, 997 and Caymans.

I have yet to deal with Hartech myself since I tend to take the masochistic DIY route but Baz Hart would be my first port of call if I found myself needing to diagnose a severe engine issue.

Baz has written a number of extensive articles  on the M96/M97 which are hosted on the Hartech web site. Links to those articles are here.


Buyers Guide Part 3 (Dyno testing - page 21 onwards)

Buyers Guide Part 4 (Boxster & 996 engine rebuilding options)

Buyers Guide Part 5 (3.6 3.8 & Cayman S 3.4 Engines)

Accusump & Remote oil filter



NOTE the picture of the sandwich plate with 6 holes drilled through it is showing the pilot holes, these were subsequently drilled out to about 7mm to ensure adequate flow capacity.

The header tube closest to the oil lines was also wrapped in header wrap to further limit heat transfer to the oil lines..

Anyone that has installed braided steel lines before will know that they can act as hacksaws and it is important to make sure that they are are secured against excess movement and that some kind of protective material is needed between the lines and any other part that the lines come into contact with. I used rubber spacers between the lines and the metal parts that the lines were secured to.

The Mocal sandwich plates use 1/2" BSP fittings.

The Lindsey racing spin on adapter uses a 13/16 (Chevy) threaded neck.

The cover plate for the sandwich adapter therefore needs to be a 13/16 item and likewise the spacer 'bolt' for the middle sandwich plate also needed to be 13/16. These 13/16 parts are available but far less common.

AN fittings with BSP threads are also far less common (most AN threaded fittings are NPT).

Oiling pressure drops during hard cornering on the track are a well known occurrence on M96 engines in 996 Carreras and Boxsters. The problem potentially increases as the car is driven harder on stickier tyres as (reportedly) oil moves away from the oil pickup under high g loads and oil pressure drops and thats not a good thing for an engine running at high RPM. Various solutions are in the market place including accusumps, deeper sumps and additional oil pumps. As I have been doing a lot of track days in the car I have decided to address this issue before it can cause terminal damage to my engine. I have chosen the accusump option. The accusump is a cylinder with a piston in it. pressurized air is present on one side of the piston (hence the gauge)  and engine oil is on the other side. The unit is then plumbed into the engines oil path. With the engine operating normally the engines oil pump fills up the accusump with oil this moves the piston along and further pressurises the air side. The oil is normally locked in the accusump by a valve which monitors the engine oil pressure, when that pressure drops the valve opens and the oil in the accusump is then forced back into the engine by the pressurised air behind the piston.  This way the accusump provides oil pressure for a few seconds of hard cornering when the oil pump might be struggling to deliver. When normal oil pressure is regained the accusump gets filled back up again, ready for the next corner.

To tap into the engine oil pathways I have replaced the standard oil filter with a LN engineering spin on oil filter adapter. Then a Mocal oil takeoff plate (sandwich plate) sits where the oil filter would typically go. Two oil lines (in and out) then run from the sandwich plat to inside the car and into a remote filter head where the oil is filtered normally. On the output port of the remote filter head there is a backflow valve then a T which goes to the accusump and to the engine. When oil pressure drops and the accusump discharges the oil cannot flow into the filter because of the backflow valve so it goes from the accusump through the T and thence into the engine at the usual filter mounting point.

The filter I have used is a billet Item from MIH which can be disassembled, and inspected & cleaned. it has its own backflow valve and magnetic element in addition to a stainless steel 30 micron filter.

UPDATE May 2012:

Connecting the oil lines to the spin on filter proved to be a major PITA due to clearance issues. I spent a lot of time and money trying different top mount and side mount adapters and AN fittings to find a  combination that would clear the coolant lines and give maximum separation from the headers and not protrude below the sump (I didn't want the oil lines getting torn off). In the end I used two sandwich plates and an extension threaded section to accommodate the middle sandwich plate. I also modified the middle  sandwich plate by drilling a series of holes through it otherwise it would have not allowed oil to flow through to the second sandwich plate. NOTE that the pic shows the pilot holes, I actually drilled each of those holes out to about 7mm or so to ensure adequate oil flow through. I then installed blanking plugs in both of the 1/2" bsp ports. This made the middle sandwich plate nothing more than a spacer to give clearance past the coolant hard pipe which would otherwise be in the way. This double stack of mocal sandwich plates gave the necessary clearance around the headers and coolant lines and did not protrude below the sump.

After coming up with this solution I completed the installation, filled the accusump with oil (& no air on the air side) and primed all the lines and the remote filter with oil, then tightened up all the AN fittings after triple checking the lines were plumbed with flows going in the right directions. Then came the big moment and I started the engine. As expected there was a slightly longer than normal delay in oil pressure building but it was only momentary.

Results..  Sadly the results were mixed. The system did operate as expected but there were a few concerns as well. On the first long drive I noticed that the oil pressure at higher RPM was about 4 Bar rather than 5 and under lower RPM the pressure was also less. I subsequently discussed this with a professional racer/builder and he was of the opinion that AN10 oil lines were too small, he used AN16 lines for his own oil system (early 911). That bothered me because I had already noted that the sandwich adapters did not really have very large oil passages and so the adapter plates themselves may simply be too restrictive for this application and I did not intend to remove the engine to drill it for AN-16 fittings into the oil gallery

One unexpected and adverse observation was that the oil lines resulted in a significant whine being introduced into the cabin because the braided lines run from the engine block to the bulkhead fittings to pass into the cabin. There was also a load dependant metallic buzzing noise which I attributed to the billet oil filter.

Something else that occurred to me was that since the oil lines are bringing hot engine oil into the cabin space, there ought to be an additional measure of protection against a rupture causing burns to the occupants. Oil lines in the cabin are not unheard of by any means but this was just one more issue that I was unhappy with.

Status...  My primary concern is health of the engine and in this case I am not convinced that the cure isn't worse than the root problem (low oil pressure in corners). Given that concern and the others I listed, I have removed the accusump and returned to a standard oil filter.


Brakes - 18 Dec    Back to top of page

The car had the brake disks, pads & fluid replaced in May 2010 prior to my buying the car and the pedal feel & braking effect is very good, better than the 02 Tip in fact. The pads turned out to be Febi Bilstein pads. whereas the 02 Tip has Textar pads and I didn't like them as much. Emmy will do some track work but the standard disks and calipers are pretty capable so  upgrades I have purchased are  limited to  GT-3 cooling ducts for improved brake cooling and Castrol SRF brake fluid for increased resistance to boiling the fluid. I have also purchased some plastic coated stainless steel braided brake lines - they also include stainless steel fittings which should resist the corrosion that is prevalent here in the UK. These may make a difference to pedal feel but are primarily intended to ensure I don't have issues getting the car registered in Australia (rusty brake lines seem to attract bad attention). Pads wise, I have some EBC Yellows on hand but I have read mixed reviews about them so I'll give them a go and see how they hold up but I guess I'm not expecting great results. I've used Pagid black RS-14s in my track car and have been very happy with those but I don't consider them suitable for he street due to their cold performance and squeal. Pagid RS-29s have a good reputation as a track pad which can be left in for street driving so I'm going down route to start with. Other options I considered with good reports were Ferodo DS2500s and Performance Friction 06 compound.

I have been doing the brakes while I install the M030 suspension and I have decided to replace the 4 hard lines between the calipers and their respective flexible brake hoses as well. One minor drawback with the HEL stainless brake lines is that they are a loose fit in the supporting bracket. The factory lines are held snug in their supporting brackets by the C shaped spring clips which you can see in the picture of the 4 hard lines. These spring clips aren't quite long enough to hold the HEL fittings snug against the bracket. So some adaptation in the form of a thick washer is required if your concerned abut it. The bracket on the front struts were looking pretty untidy as well so I de-rusted them with a wire brush and some de-ox gel (the other parts in that pic are front strut components which I cleaned up at the same time). One of my pet hates is brake fluid dripping out continuously so I used a couple of the old hardlines to make plugs ie I hammered the middle of the hard line flat then cut the line in half with pliers and screwed one half into the open brake line so that it didn't drip while I worked. For the brake fluid swap I actually put in a fresh 1L can of ATE Blue and after the hydraulic lines had been filled/bled with that I cleaned out the bleeder and filled it with 1L of SRF and was able to complete a fluid swap with just that 1L. So in effect the ATE blue was used to flush the lines and draw out any moisture in the bleeder/lines and because it was blue I had a good indication when it had been flushed out by the SRF. These Motive power bleeders are fantastic and I can't recommend them highly enough. The final pic in the series is the new GT-3 brake cooling ducts installed.



Pagid RS-29 pads (Feb 2011) . I have run Pagid RS-14 blacks (v good) and Pagid blues (I didn't like these so much) on my 951 but have not tried RS-29s As of Feb 2011. I am going with RS-29s bought from Performance Braking for the 996 due to them having a good reputation as an effective track pad that can be left fitted for normal street driving with minimal squeal. This will save me the effort of swapping pads out on track days which will be nice. If the squeal is too bad I guess I'll be going back to the pad swap option but I'm not keen on that idea since it will involve a bigger effort to clean discs and re-bed in pads.

Bedding in Process: Here is the Pagid bedding in process as well as some generic but informative articles including an excellent video. Pagid  Stop tech 1 Stoptech 2   Video 


The pics above show a  comparison between a set of EBC yellows which I have on hand and Pagid RS-29s for a 99 C2.

Ferodo Application List for Porsche FRP3051 -FCP1308 - 

My experience with bedding in RS-29s....

In order to get the most out of my RS-29s I went through  the entire procedure Pagid recommends including sanding the discs to remove existing pad material. That was easy enough for the face of the disc which you normally see - just use a sanding block and some 80 grit emery cloth. The back face of the discs is mostly covered by a stone shield though. For the fronts there is a gap in the stone shield near the top of the disc and you can get the sanding block in there for the rear discs you pretty much have to hold the emery cloth against the disc in the space where the pad slides into the caliper. It didn't take more than a few minutes to sand the face of each disc. I also inserted to wheel bolts into the rear hub and then used a lever between them to rotate the disc easily whilst I held the emery cloth in contact with the disc.

For the bedding in I followed the Pagid driving procedure listed above. I was surprised to find that there was not as much material transfer/dust/smoke as I expected and I suspect that I was leaving too big an interval between braking events. I have extra cooling ducts as well so that wouldn't have helped. Hence I will have to repeat the process to achieve a more uniform bedding in. The pics do show that at least a part of the pad got up to temperature as evidenced by some ash on the edge of the pad and the corresponding part of the disc shows the best blue-ing / pad transfer. A close look at the edge of the pad also shows some brown discolouration which gets less towards the hub edge - clearly the pad was less hot in that area and not as effectively bedded in - this is backed up by there being less blue-ing / pad transfer to the disc in that area.

I didn't experience any squeal initially, however once I washed the car and the rotors picked up some surface rust I did get some squeal in the last few yards before coming to a stop. This went away again when I did another bedding in session.

The braking effect already feels very good and and that should get even better. I was surprised that even when cold they still feel quite ok.

I didn't experience any pad fade, which is not surprising since the pads clearly didn't get fully up to temp. There were also no issues with boiled fluid/spongy pedal (Using SRF).

After this initial session I am hopeful that the pads will stand up well to track duty.


One other point is that I have tied back the brake wear sensors (5th pic) since they may have a tendency to melt during a hard braking session at the track.

The pics below show the results from another bedding in session. The brakes were warmed up by conducting a few medium pressure slowdowns from 70mph then a series of 5 firm pressure slowdowns (bordering on ABS intervention) from 110 to 40mph. After each firm slowdown I pumped the brakes lightly 3 times with my left foot whilst accelerating back up to 110 for the next slowdown. The pics below show that the pads got more heat into them as evidenced by the brown discolouration extending all the way across the pad towards the rotor hub. There is also more pad transfer onto the disc itself.

Sep 2011: In bedding in my second set of RS-29s I followed the Pagid procedure pretty carefully ie 90-50 5 or six times then inspect the rotors for good coverage, I did 90-50 another 5 or six times, inspected them again, then did 3 runs of 110 to 50 with threshold braking. After this effort the discs were still only lightly coloured and the pads were not really showing any heat discolouration at all. Clearly a greater number of runs is required. I did another set of the 110-50 runs and got a little more colour on the pads but I would still hesitate to call them fully bedded in.

Brake disc micro cracks - July 2011

Now that the car has been running the RS-29s for a couple of months and several track days, the discs have started to develop micro cracks in the surface of the disc. That's not too bad considering some people find that they can start seeing such cracks in drilled rotors after only 2 days. Micro cracks tend to occur on drilled discs rather than slotted discs. After these appeared I talked to various people who had been tracking Porsches for a while and the consensus was that they are a common occurrence and no particular concern until the cracks get beyond certain limits, join up or reach the edge of the disc. So these are something I'll keep an eye on and inspect each time I prep the car for a track day.  

Guide to evaluating rotor cracks

The picture above is a higher resolution pic of the cracks in the Porsche OEM brake rotors.

As can be seen from the pics of these same rotors taken earlier in the year, there are no such cracks.

Brake Update Sep 2011

It's been 7 months since I installed the first set of RS-29 pads onto the car. In that time I have done about 10 track days and covered about 10K miles. The pads are now completely worn at the front left wheel. Interestingly  the inside pad has a noticeable taper as can be seen in the attached pic. I assumed that one of the pistons might have been sticking but I popped them out and both pistons on that side were in pretty good shape. Likewise the other two pistons move freely with just a few psi of air pressure from a bicycle tyre pump. The drivers rear was the next most worn set - even wear with about 4mm remaining. The drivers front and passenger rears were also worn evenly with about 5-6mm remaining.

Whilst the wear has been a bit faster than I expected, it would be fair to say I have been guilty of over braking whilst getting to know this car on the track, and since the brakes are 318x28mm, they are decent sized but not exactly in the 'huge' league. Now that my braking is a bit less aggressive than it was to start with, I think I'll stick with the stock rotors for a while. My main impetus to change them will no doubt come from excessive cracking and/or a desire to save weight with 2 piece rotors if possible. At this point the front rotors are showing cracks up to 7mm long (i.e they have reached the limit), the cracks appear mostly on the outer face of the rotor. Cracks are evident on the rear rotors as well however they are not as extensive as on the fronts. Basically where there is more brake cooling there is less cracking and where a particular disc is working harder there is more cracking as well. I noted that the heat load on the disc can vary if the pad contact patch is not even - seemingly because the heat stress is concentrated in a smaller area and that cracks more.

I decided to get the discs skimmed in preparation for the new pads. I am mindful that the life of these discs is going to be rather limited given the cracking so this was a conscious decision to look at the effect of the skimming on the cracks and to ensure that my new pads don't start life on an uneven disc surface. The front disc wear was at 27.6mm at it's low spot.

Front Rotor weight after skimming to 26.6mm 7.6kg, Rear 6.3kg. The skimming took away more material than I expected , the discs are now 0.6mm above the wear limit (2mm total permissible wear). Whilst the weight drop is reasonably significant (8.2kg to 7.6kg) I am conscious of the fact that the missing weight is missing from the friction surface not somewhere less relevant like the hat, so there is less heat absorption capacity, not necessarily a good thing at all

16 Sep 2011: Installed new front Pagid 318x28mm standard rotors in preparation for next track day... Must bed them in this weekend.

Update Feb 2012: I've concluded that I'm not overly happy with the RS-29s. Whilst the pads have been effective on track, the pad wear rate I've experienced with the C2 drilled disks has been on the high side. What also irks me is that I experience a fair bit of brake shudder despite good efforts to bed these pads in properly and maintain clean rotors.

Parking brake adjustment.

Since I had the rotors off I thought I would get a few pics of the adjustment mechanism for the parking brake. Usually  it helps to retract the parking brake shoes by winding the star shaped adjuster in the appropriate direction prior to reinstalling the rear discs. See pic to ID which is the correct direction to wind the adjuster. Comments are relative to a RHD car. Note that the adjuster is still accessible with the rotor in place (it has to be) even though the pic shows the adjuster being adjusted using a screw driver whilst no rotor is fitted. Also note that it is the adjacent spring which acts as a detent mechanism to stop the adjuster moving unnecessarily through vibration.

Disc re-surfacing



As can be seen the resurfacing does not eliminate the cracks - except perhaps on the rears which were only lightly cracked to begin with. End result was that this was not a worthwhile activity in my view.

2 Piece Brake Rotors.

Since my brakes are due for replacement I have been looking into the benefits of 2 piece rotors & bigger brakes overall. As of Sep 2011 I have elected to continue using the stock calipers & discs. However I thought I'd share the information I dug up in the process. The following information was gleaned from various threads at Rennlist and is reproduced here for convenience.

Performance Friction discs and pads (PF-06 in particular are highly regarded both here in the UK and in the US, especially amongst the GT-3 fraternity) PF 2 piece rotors come in a street version with dimples and a motorsport version with slots. Both are very good. Both use the same hat and the discs for both begin life as the same part.


318mm C2/C4 sizing Performance Friction 2 piece street rotors (Iron hat) The use of an iron hat on the 318mm rotor (318 is stock size) is related to hardware clearance issues. From my own phone conversation with PF Europe (based in UK), they can do an aluminium hat rotor if you go up to 330 (it may have been 340mm) rotors, but as per Giro discs, that would necessitate use of spacers on the caliper as well. The PF rep highlighted that the fasteners on the iron hats are blind which is OK but that aluminium hats are not strong enough to use blind fasteners - that's why you can see both ends of the fasteners on 2 piece rotors with aluminium hats. This does suggest to me (I haven't verified it) that any pad which fits the OEM rotors would work with the 318mm PF rotor with iron hat.)

 These pics show the difference in pad construction between the PF pads and other brands. The PF pads are not as tall and thus clear the hat hardware (in discs with Aluminium hats) whereas other pads may protrude further from the caliper and interfere with the hat hardware.

Other notes for future reference:

Girodisc Rotors 7.8kg - Al Hat, 340mm disc, 12mm spacer, use with Pagid pads.

PF F 318x28 9.2 kg  (Cast iron hat 2 piece)

OE F 318x28 8.3kg

OE R 299x24 6.5kg

OE F 350x34 11kg (24.2lbs) ?

OE R 330x28

PF F 350x34 Dimpled 9.1kg (20lbs)

6GT3 330 Rear Cup 9.1kg

6GT3 350 Front Cup 9.7kg

PF 2 Piece Rotors in GT-3 sizing.

In the pics above the first one is a motorsport slotted disc whereas the others are the street dimpled versions. Also included is a pic one rennlister posted showing slotted discs he used until the slots were completely worn down and even then the cracking was acceptable.

PF Street Rotors Link at Rennlist

PF Motorsports Link at Rennlist   Post 15 includes part numbers

PF Street rotors (GT-3 sizing) vs GT-3 Cup rotors link at Rennlist

PF Hardware set (Direct Drive V1)

Note to self - The slotted discs come with HD hardware which is twice as expensive as the street version. That hardware set does allow the disc to float as well, so they are noisier. The dimpled/slotted rotors begin life as the same blanks, the hats are the same.

Giro Disk information

      (Pics from Dervish's post at Rennlist)

Giro Disk data sheet

Giro Disc Technical information

Giro Disk thread on Rennlist

March 2012: My Big Brake Upgrade.

I have held off upgrading my brakes for a long time on the basis that I had lightened the car and the common view that the 996 C2 brakes are adequate with good pads & fluid. After 15 or so track days I am not convinced that the brakes are as good as they should be. With C2 brakes and RS-29 pads I certainly don't find them as good as the 993TT brakes fitted to my 944T (using RS14 pads). I have also been dissatisfied with the regular occurrence of shudder despite careful bedding in and avoidance of pad imprinting at the track as well as the relatively high wear rates I have experienced on my rear pads. With those issues in mind I have elected to upgrade the brakes to 996 GT3 MKII standard ie 6 Pot 350x34mm front and 4 pot 330x28mm rear (From 318x28 & 299x24). The Front brakes were obtained as a caliper & mounting kit (only) from Rudtner Racing in NY, USA.

Front: This is a modified 6 piston GT3 caliper and an adapter bracket and a standard cross drilled Porsche GT3 350mm x 34mm rotor. The C2 caliper has mounting bolt hole spacings of 130mm but the GT3/Turbo/C4S calipers use a 142mm bolt hole spacing on the front caliper, hence the need for a modified caliper and mounting bracket. The other option is to replace the wheel carrier assembly but that can get very expensive and its very hard to find them second hand. The caliper adapter stud(s) screws in as far as it will go and then is backed out a fraction of a turn until it lines up with the slot in the spacer bar. the spacer bar is actually thicker than the oval shaped part of the stud in order to allow the stud to be partially backed out. Ultimately it is the Nut on the end of the stud that will lock the stud threads against the threads in the wheel carrier/upright. With the new caliper in place it is also necessary to use a new hard pipe to join from the caliper to the flex pipe at the bracket to which the flex pipe reaches. (see parts list). UPDATE (May 2012) I just realised that these calipers are incompatible with my sport classic II wheels unless a wheel spacer is fitted. I've always used a 15mm spacer with my SCIIs hence this late discovery. I'd say a smaller spacer would be adequate i.e. 7mm or so.

Rear: I moved  my C2 front calipers to the rear and using a 4mm spacer because that caliper now operates on a 330mm disc which is 12mm greater diameter (6mm greater radius) than the 318mm disc that the caliper was originally designed for. I had expected to need a 6mm spacer but 4mm is what aligned the pad and rotor surface to have the best fit. OEM GT3 77mm bolts were substituted for the C2 72mm bolts. Note that the usual rear caliper had a tapped hole for a screw to secure the brake line bracket. By moving the front caliper to the rear there is no such tapped hole. Because there was no way to attach a bracket for a short hard pipe I eliminated the M10x1 ISO bubble flare hard pipe and instead I utilised a M10x1 convex union (caliper union or male-male joiner) to connect the flex line to the caliper. This connection must be checked for leaks and it is important to ensure that the coupler does not bear any load from the flex pipe that may cause it to break or loosen.

The C2 front caliper uses the same pad  sizes as the GT3/Turbo rear calipers, BUT, the piston sizes for the C2 front caliper are 36/44mm and that is substantially bigger than the 28/30mm pistons that are used in EVERY other 996 rear caliper. Since the piston size directly effects brake bias, I have substantially increased the rear brake bias by doing this caliper swap. This bias does need to be addressed. I have tracked the car with the bias like that (once so far) but it should be borne in mind that the Carrera uses a rear brake circuit proportioning valve (5/55) to limit the increase in rear brake line pressure to 0.46 of front brake pressure above 55 bar (800PSI). NOTE - the GT3 does not have this proportioning valve so a C2 front caliper on a GT3 rear axle could (& probably would) create too much rear brake bias and cause the car to become unstable under heavy braking). With a 5/55 bar proportioning valve I did feel some (a little) rear end instability under braking and it is worth noting that I have a freshly built 40/60 LSD with GT parts that would normally keep the rear end firmly planted. So my next move is to investigate reducing  the rear braking bias a little to keep things stable but also to retain a decent amount of rear braking contribution to slowing the car down. For what it is worth I have been calculating the brake front / rear bias percentages of various 996/997s and have compiled the following  table:

996 GT3 Mk1 0.65 / 0.35

996 GT3 MkII 0.65 / 0.35

944T 0.56/0.44 plus 5/18 bias valve (& these are commonly replaced with a 5/33 bias valve)

My 944T with 993TT big reds front 0.58 / 0.42 (5/33bias valve)

997 GT3 0.58 / 0.42

996 STD 0.64 / 0.36 (5/55 bias valve)

My 996 0.53/0.47 (5/55 bias valve)

Rather than installing an OEM 5/45 or 5/33 proportioning valve I will be installing a Tilton 7 step adjustable proportioning valve. It lets me choose the knee point (point at which pressure reduction kicks in) and it then limits further pressure in the rear circuit to 0.33 of the pressure increase in the front circuit. This all has the effect of fully using the rear brakes under light to moderate brakes but during threshold braking the reduced rear pressure prevents lockup of the rears before the fronts - especially since threshold braking unloads the rears and makes them more susceptible to locking as well.

Plumbing in a 5/33 valve or the Tilton valve turns out to be a trickier issue than it first seems. The Issue is that the OEM 5/55 valve uses M12 fittings and 1/4" brake line tube whereas the 5/33 and Tilton bias valves use M10 fittings designed for 3/16" brake line tube (same as we see at all the calipers). The fittings from the MC to the bias valve are M12 and the fittings from the bias valve to the ABS are M12. I have spent many hours searching (to no avail) for a M12x1 male to M10x1 male union (like the brass fittings on the right but M12 on one side & M10 on the other). Likewise I was unable to track down a M12 female to M10 male metric brake line reducer. These fittings if available or manufactured (Sigh.... I miss my lathe) would simplify the installation of these alternative bias valves. Given these constraints the next most feasible approach is to use 3/16 brake line with M12x1 male fittings on one end and M10x1 brake line fittings on the other end. These lines can be done as a DIY if you buy a Metric ISO bubble flare flaring kit plus the kunifer brake line and brake line fittings (these parts can be most easily obtained from ebay) These fittings will allow the Tilton valve to be plumbed into the M12 circuit. (As of May 1012 I have the parts but am yet to install the Tilton valve as I am waiting on the opportunity to evaluate the brake performance on-track under varying conditions with the 5/55 in place)  If these options don't prove satisfactory there will be the option of using a 996 GT3, 996 Turbo or 997 C2S standard rear caliper as these are also designed for a 330x28mm rotor and uses a 130mm bolt spacing along with a 28/32mm piston size.

Master Cylinder

The C2 Master cylinder (MC) is a 23.8mm piston sized with an 18mm stroke. The GT3/Turbo item is a 25.4mm piston with 18mm stroke. The bigger piston size results in less brake force but moves more brake fluid which translates to less need for pedal movement. I initially ran the brakes with the C2 MC and it did work but I wasn't satisfied with the pedal travel and sensitivity (it was too easy to overbrake & hard to be consistent with brake application under track conditions) That was with the C2 booster installed as well (exacerbating the sensitivity). So I have now obtained a 25.4mm MC to replace the C2 unit. The 25.4mm NC is expensive from Porsche, but after considerable research and many false starts I identified an MC listed as an Audi part with the needed characteristics. BEWARE that many MCs 23.8mm MCs are incorrectly listed as being suitable for Turbo/GT3 cars so it is imperative to verify the physical appearance and piston size for the part being ordered- don't rely  on the manufacturers claim about vehicle fitment. I found the part for about £90 delivered from LINK  The Lucas part number for the MC is 8D2611021 and the Italian suppliers part number was MC1026BE. This MC works fine, the only thing I didn't like about it is that it is a cast iron part rather than a cast alloy part - but for the £300+ price delta I can live with that. When installing a new MC it is advisable to 'bench bleed' it to ensure it is completely evacuated of air bubbles prior to fitting it to the car. I didn't do it initially and so I had a pedal that was not as firm as I would have liked after any decent use. So I ended up removing it to bench bleed it and then I re-installed it. Search on you tube for bench bleeding master cylinder to get a feel for what is involved. My new MC didn't come  with a bleed kit so I made one as per the pics.

Brake Booster

The Porsche 996 C2 & Turbo use a brake booster (Brake Servo) made by Lucas with a boost factor of 3.85. The GT3 uses a lower boost factor of 3.15 (Porsche part No 996.355.923.90). The lower boost factor and bigger MC piston size translates to a brake pedal that needs more effort and enables the driver to have a better feel for the brakes under track conditions. I looked for a used GT3 booster for a while to no avail so I found a new supplier (TRW) at this LINK  where I bought the booster for about £290 delivered. TRW part number PSA111.

Impressions:  When I drove with the big brakes and high boost servo and 23.8mm a light touch on the pedal made for a lot of slowing down. That's ok for road driving where light pedal pressures are used but for track use your often on the pedal hard and using it as a pivot for heel & toe. When I swapped in the lower boost servo and 25.4mm MC the first impression during road driving is that the brakes are not as effective. Of course they are effective but it takes more pedal effort to slow the car down - consequently, when it comes to on track performance you can stand on the brakes harder and use the brake pedal as a pivot for heel & toe without inadvertently over-slowing the car. That is the effect I was looking for so it's all good. It's also worth mentioning that since going to these brakes and PFC pads I've had none of the brake shimmy that I was getting with my standard brakes and Pagid RS-29 pads.



Parts List for 6 pot brake upgrade & caliper swap

Rudtner racing Modified Porsche 6 piston caliper & custom mount kit
350x34mm 996 MkII GT3 front brake discs. OPC
PFC 08 Brake pads Front / Aftermarket
330x28mm 996 MkII GT3 rear brake discs. OPC/independent
PFC 06 pads in 996 C2 front sizing = GT3 rear sizing. 0776.06.17.44 / aftermarket
M12 4mm spacers x 4 generic / aftermarket
77mm GT3 caliper bolts x 4 999-067-042-09 / OPC
Pin/spring kit for 6 pot caliper 996-351-959-30 / OPC
Front caliper hardlines (L&R) 996-355-581--9B & 9A. /OPC
Male-male m10x1 convex unions x 2 /Merlin Motorsport UK

Optional but recommended:

Brake booster TRW PSA111

Master Cylinder Lucas 8D2611021

Proportioning valve (OEM or Tilton) - Note fitting these proportioning valve will generally involve quite a bit of research to find suitable connecting hardware and will likely involve some custom brake lines being fabricated.

Good brake reading

Stop Tech on brake testing

Stop tech technical white papers (Knock back, ABS, proportioning valves etc)

Brake Bias  (Bias spreadsheet / calculator)



Stripped caliper mounts / uprights (Noteworthy for 997 stripped caliper mounts)

   March 2012

Ok, so I play with my car more than most. That means my calipers have been on & off more than most and also it means that the threads (in the wheel carrier)  for one of the caliper mounting bolts got weak and stripped. Bugger. I recently had a very expensive track alignment & corner balancing & I didn't want the time or cost of messing with the alignment again so I wanted to repair the threads without removing the wheel carrier. BUT I also didn't want a poor quality thread repair that was less than perfect because this is for a caliper bolt and it is imperative that correct caliper to rotor alignment is preserved in order to avoid shudder/knock-back etc. There is limited space in the wheel arch so I had to get creative to come up with a solution that is accurate & effective.

The simple but effective solution was to have a Steel jig machined with a 12mm hole and a 12.4mm hole spaced at 130mm (I also had a second pair of holes drilled at 142mm for GT3/Turbo spacings). The 12mm hole aligns the Jig & the helicoil 12.4mm drill then goes squarely through the other hole to drill out the old threads. The jig is then stood off the mounting points using some spacers so that it then serves to align the helicoil tap squarely with the freshly drilled hole. A right angle 13mm drill was hired to take care of the drilling. With all this prep the drilling was a 5 min job. and the helicoiling wasn't much more. The results were spot on with a better than new repair.

Rear Brake Ducts

I installed GT3 rear brake ducts on my car. These attach onto the lower coffin arms via a plastic U shaped bracket. Two notes with installing these.

(1) The brake backing plate  needs to be trimmed back (remove rotor & caliper first).

(2) The ducts themselves needed relief's to be cut into them to avoid interference with the GT3 sway bar & drop links. They are pretty tough plastic but can be done with a dremel.

May 2012 - To be honest I expected that I might have some clearance issues with these brake ducts but that has not proven to be the case. I've recently had a trip into the grass which was enough to break my front splitter and front brake duct and fill the rear with grass and dirt but it remained firmly in place.

Brake results / impressions - May 2012 Update. Performance Friction Pads.

I haven't been using the car an awful lot for the past 2 months which means I've only had a limited number of opportunities to evaluate the brake performance and any ill effects from the larger than normal piston sizes I have as a consequence of relocating my C2 front calipers to the rear. Conventional wisdom (aka lots of forum observers) suggested that putting my C2 front calipers on the rear would increase the rear braking bias to an unacceptable level and the 'system' would not be safe/effective. The logic of that view is not unreasonable and I have been mindful of it whilst driving the car at the track because I have no desire to create an unsafe condition where the rear wheels lock under threshold braking creating an increased potential for a snap spin.

My initial track event with the car was in cool but dry conditions at Oulton park with the C2 Booster & Master cylinder. I found that it was difficult to properly modulate the brakes without over braking so I changed the booster & MC to GT3 items. That alleviated the over braking issue because the reduced booster and bigger MC require the driver to use MORE brake pedal pressure to slow the car down & that eliminates the tendency to over-brake. To a certain extent it makes the brakes feel like they are less effective compared to the big booster and smaller MC. Of course that is not the case, there is plenty more brake capacity if you want to press the pedal harder.

The  next event was at Spa but it was only a half day, I used front PFC 08 pads and rear EBC Yellow pads because the EBC yellow pads are less aggressive and thus reduce rear brake bias. The high speed sections require braking from around 140mph down to 70 Mph and I noted a little bit of tail wiggle under those conditions. However I have since noted about the same level of tail wiggle in a friends GT3 MKII at Donington which is set up similarly to mine in terms of suspension and LSD (His is fitted with 6 pots & std rear GT3 calipers).

The next event was at Snetterton in the wet where I did a full day, again using the PFC 08 front & EBC yellow rears. This was an excellent test because if the rears were going to lock early from excessive rear bias, it would have shown up under these damp conditions. Happily there was no evidence of the rears locking up early and the car was stable including during a few laps where I had to threshold brake during a corner entry for a car that was slowing more rapidly than expected. At the end of the day the car showed considerably more front brake dust than rear brake dust (partially related to different pad compounds) but most tellingly the the rears were not as extensively blued as the fronts and the fronts show typical moderate cracking already whilst the rear discs have no sign of cracking. My previous experience with standard brakes and RS-29 pads was cracking on front and rear rotors, even blueing on both rotors and surprisingly more brake dust on the rear wheels.

So at this point I'm of the view that the car is plenty stable and it looks like the combination of a standard 5/55 rear bias valve and less aggressive rear pad is under-utilising the rear braking potential of the 350/330mm rotor setup. That being the case I will revert back to using a PFC 06 rear pad for my next track day.

Follow Up June 2012:

I've done another 3 track days using PFC08/06 at Oulton and PFC08/EBC Yellow at Snetterton & Oulton. All were dry conditions. I had Mike Wilds (Professional racing driver) drive my car several times and he was of the view that the brakes were perfectly fine. His driving style is smooth but pretty aggressive with some heavy braking over shorter braking zones than I had been using. Under these conditions the brakes did not exhibit any undesirable traits attributable to excessive rear bias. Mikes results and assessment of the brakes were a good professional and independent endorsement of the system as I have it. I have noted that the rear PFC 06s are the primary contributor to the significant cold brake squeal I have. When EBC yellows are fitted to the rear there is not much squeal at all.

Brake temps

I have started to take some brake temperature measurements and will periodically update this section as collect some data using a consistent methodology.  The readings below were taken at various times of the day(s) generally after a session where the brakes had been well used. Some readings will have had a full cool down lap beforehand and the hotter readings generally involved less than a full cool down lap.

Snetterton 14/05/12 damp 16c PFC 08F 06R   180/180c 240/240c and F211/R200c

Oulton 20/6/12 Dry 22c  Using PFC 08F and EBC Yellow rear -  F318c/R370c : F244c/R255c : F229c/R295c 

R32 Skyline (F346/R281c and F239/R241c) carbotech pads OE disc/calipers

Brake bleeding & dealing with a persistent soft brake pedal.

For a long time I have felt that my brake pedal was softer than it should have been in comparison to other cars. I also had other drivers track my car and they agreed that the pedal feel was softer than it ought to be.

It is normal to have the brake pedal feel very hard with the engine off and it is normal to have the brake pedal have a bit of give before resistance is felt once the engine is running.

In my case, after bleeding the brakes the pedal was hard prior to engine start but would go nearly half way to the floor before feeling any significant resistance. - that was my starting condition and it would deteriorate a bit further once I got to the track. I never had the pedal go all the way to the floor, I never had pad fade or fluid fade but at the track the pedal just did not feel 'encouragingly' firm.

I should add at this point that I was bleeding with a Motive bleeder and I was using SRF fluid and Pagid/PFC pads and I had decent brake cooling. So none of those things were the issue.

That's when I set about my effort to eliminate the problem. To cut a long story short I will list the things that were necessary to resolve the problem. Not all of these steps will be necessary for everyone - they were necessary for me because I had swapped out various brake components (Calipers, lines, master cylinder, booster and proportioning valve). Although the pedal softness was noted from my very first track day in the 996, not just after changing t hose components. I bought a 5 litre budget brake fluid so that I could do multiple flushes at low cost and then I finished the process by doing 2 bleeds using 1L of expensive Castrol SRF each time.

  • Bench bleed the master cylinder.

  • Adjust the pushrod to the brake booster if necessary (this will influence the pedal height). see next Pic. Adjustment procedure is in the workshop manual.

  • Re-tighten all brake line connections to the flex lines and calipers, master cylinder and proportioning valve. (Some slightly loose connections at the flex lines I believe to be the root cause of gradually letting air into the system)

  • Ensure all bleed nipples are tight after bleeding. (With mechanical sympathy in mind I usually snugged up the nipples whilst trying to avoid over-tightening them - now I make sure they are quite tight). I also dry the nipples with paper towel thoroughly after bleeding so that I can detect if they are sweating any fluid later on (now that I tighten them they do not sweat, sometimes they used to).

  • Do at least one pressure bleed which includes fully squeezing each pad/piston set back as far as it will go whilst its corresponding bleed nipple is open. This is to ensure that no trapped air bubbles are sitting in the cavity behind the pistons. (After this bleed is finished the brake pedal will need quite a few pumps to bring the pads back into contact with the discs and the fluid level will probably need topping up).

  • Bleed the brakes with a combination of applied pressure from a motive bleeder and pedal pumping for each caliper.

  • Drive the car on a loose gravel surface with 8-10 stops from slow speed (ie 1st gear / 10-15mph) which activate ABS. This is more effective & easier on the car than a bunch of hard stops from 80mph.

  • Bleed the brakes again with motive pressure and pedal pumping.



FLUID CHANGE - How much to flush ? When switching between ATE blue and SRF it became apparent that about 2L of fluid is the minimum needed to clear all the blue out of the system. I suspect that is mainly a result of the fact that some mixing occurs so it is not just a 1 for 1 swap in volume terms. One trick for minimising mixing is to apply pressure to the fluid reservoir and then open up one of the front brake bleeders until the fluid level is almost empty, then repeat the process for a rear brake bleeder - obviously you need to be careful not to let the fluid level in the MC completely run out or you will be pumping air into the MC.

How to do the brake bleed ? I bleed with a Motive pressure bleeder at 2 Bar. I ensure that there is always a minimum of 1/2" of fluid in the bleeder bottle (I pour in 1L at a time) so that air bobbles don't get pumped from the bleeder into the reservoir. I check the fluid once it is poured into the bleeder bottle to ensure that it is free of air bubbles. I also tap the bleeder bottle a few times and let it stand for a good while (Go and have a coffee and check your emails) to ensure that there are no air bubbles clinging to the sides/fluid intake. I then open the bleeder valve (Right Rear) barely 1/4 of a turn then I go and press the brake pedal all the way to the floor hold it there 3 seconds and then slowly ease it back up. (cars with old master cylinders may experience seal failure by doing this - my MC is new though so no corrosion and no risk of corrosion at the end of the piston stroke ruining the seal) I repeat the pedal action 3-4 times. The pedal pumping against a barely open bleeder valve creates high pressure which will move along all the stubborn air bubbles (motive pressure alone may not achieve this in some cases). I then close the bleeder valve, swap the collection bottle to the other nipple on the same caliper, open it up no more than 1/4 turn, and repeat the brake pedal cycles. I then close the nipple. I check the bleeder bottle fluid level and pump it back up if necessary and then I repeat this cycle on the other rear caliper. When the second rear caliper has been done I pump the bleeder up again, make sure it has plenty of bubble free fluid and begin on the front calipers using the same process.

WARNING: Some people report that the clear plastic lines on their motive bleeder have burst and sprayed fluid every where. I have not experienced this myself but it is probably worth replacing those lines every few years. Some people just use the motive bleeder to apply pressure rather than filling it with fluid. That does eliminate the risk of a burst line spraying brake fluid everywhere but it does necessitate that the fluid in the reservoir gets topped up far more frequently and obviously the motive bleeder has to be disconnected and pumped up after each filling of the reservoir.


Constant stream of fine bubbles. When using the power bleeder it is not unusual to observe a constant stream of bubbles emerge from the caliper - this is indicative of air being sucked past the bleed nipple threads. This is not something that needs to be worried about. It is not necessary to try and seal the threads. with grease or tape. When pressure bleeding that air never gets past the nipple into the caliper. The stream of bubbles does make it a little trickier to spot 'real' bubbles that have come out of the brake lines but it's not that hard. The real trapped bubbles tend to momentarily interrupt the constant stream so you can still recognise them coming out.

Performance Friction Pads - impressions: Jun 2012.

I have been running PF 08 Front & PF06 rear pads for a couple of months now. I have to say that I am liking these pads a great deal more than the Pagid RS-29 pads. Whilst I had previously been happy with RS-14 pads, I cannot say that I was overly happy with the RS-29s due to wear rates, brake shudder and the extra hassle of bedding them in. The PFC pads have performed well and I have not had any shudder issues and no time spent bedding them in yet they have shown a nice even pad transfer to this discs. My only complaint has been that the PFC 06 rears squeal a lot in my setup.


Performance Friction 2 piece discs June 2012

When I installed GT3 6 pot calipers up front, I did so with a set of barely used OE 350mm drilled discs which I managed to pick up at an attractive price. That approached saved having to fork out £1k or so at the time for the PF discs I would have really liked. That was in March and its now June and the OE discs have reached their crack limit over the course of the 5.5 track days I have done in that time. I have managed to pick up some part used PF 350mm 2 piece dimpled discs for a bargain price of £125 which includes a set of half worn PF pads (type unknown unfortunately). Whilst I would have preferred a set of slotted discs, this was far too good an opportunity to pass up and so I will utilise this set of rotors and when they are done I'll re-use the hats and just purchase the slotted rotors and a hardware kit. These PF rotors are 1.9kg lighter than an OE 350mm 1 piece rotor, not only that but they will last a lot longer and thankfully wont need the holes cleaning out before each track day.

When I took the calipers off to install the PF rotors I found that all six the seals on the LHS had been heat effected (this is the outside wheel for the tracks I go to) whereas all six seals on the inside caliper / wheel  were fine.

Front Brake Cooling Revisited: July 2012

Whilst I had taken various steps to improve brake cooling, the toasted piston seals seen above along with the ongoing issue with my brakes feeling a bit soft after hard use and the expense of replacing pads & rotors has prompted me to up the ante in the brake cooling stakes. That means I have switched from 996 GT3 brake ducts to 996 Cup brake ducts which are considerably larger (& considerably more expensive I might add). I also ordered some 997 curved deflector plates and modified them slightly by cutting a slot for the steering arm to pass through. These are then zip tied into place at a couple of convenient points. Before doing that I removed the wheel arch liners so that I could access the radiator shrouds and I trimmed away about a 4x6 inch square section at the rear of the shroud to allow exit air from the radiator to flow rearwards towards the deflector plate. The radiator shroud in the 997 lets the air flow rearward but on the 996 it directs the air downwards. I then trimmed a section of the wheel arch liner away so that the air from the rad/shroud can pass into the wheel arch where it will subsequently reach the deflector plate and be turned towards the rotor/caliper/brake lines.

Part numbers for 996 cup brake ducts are
996 341 117 90 L
996 341 118 90 R

Brake duct comparison & discussion at Rennlist


Pic 3 

These are the 997 deflector plates I installed. Note that the slot for the steering arm needs to be wider than you might first imagine to account for the fact that the steering arm moves fore/aft as well as from side to side. It's worthwhile securing the deflector plate in place and then noting the position of the steering arm at both ends of steering lock - that way you'll know how wide to make the slot. I didn't want o cut away too much of the curved part of the deflector so I positioned it rearwards enough that the slot only just reached the curved part of the deflector. Then with the deflector secured at that point I put opposite lock on the steering (Pic 3) , noted how far forward the steering arm traveled and I then cut out the notch to accommodate the arm in that position.

By using zip ties the deflector can be positioned effectively and it also has a bit of give in the case of extreme suspension travel.

Rear caliper swap to GT3 (Jul 2012).

As can be seen above I went from a stock rear caliper to using my front caliper on the rear (so that I could use 330mm rotors) and now I have picked up a pair of 'correct' rear calipers i.e. These are calipers of a 997 2010 C4S which are the same as a 996 GT3/996TT and use the Porsche 996 standard rear piston sizes of 28/30mm. These calipers will provide a more traditional brake bias (more bias to the front). The other benefit is that they have the correct brackets and fixings to support the brake lines which the front calipers did not (when used on the rear). They also happen to be red with fresh seals which is a nice bonus. Like all the 996/997 rear calipers the mounting bolt spacing is 130mm. As these calipers are designed for 330mm rotors they do not use spacers but I might try these calipers with 350mm rotors in the future so I'll be hanging onto my collection of spacers.

Proportioning valve delete (Jul 2012).

Since I have restored the standard (GT3 MkII) brake bias to the car in terms of relative rotor / caliper size, I also went ahead and deleted the proportioning valve. The proportioning valve is standard on the Carrera and Turbo but it is not fitted to GT3s. The proportioning valve reduces rear brake force which is good for street cars because it is inherently safer/more stable but for a track car the proportioning valve means the rear brakes are underutilised and a track car generally has a decent LSD which does help to keep the rear end stable under heavy braking where rear brake force can potentially raise it's head as an issue (the issue is that you don't want the rear brakes to lock before the fronts as the car will want to swap ends if that happens).

To delete the prop valve I bought an M12 convex female-female brake line joiner (BQ147 from Brake quip) and then I manufactured a new short length of brake line using 6mm kunifer tubing which I bubble flared and fitted with M12 brake nuts to go from the joiner to the Master Cylinder.


Intake / Air Filter 29 Jan 2011

Early on I tried a Fabspeed Carbon Fiber Competition CAI and I quickly formed the opinion that it was overpriced, poorly designed, fit badly and complicated access to the engine.  It did actually improve power by 5Hp right at the top of the RPM range but it also provided less HP at various points across the RPM range as well. Overall there was no useful gain as  measured on the dyno. That also came at the cost of being annoyingly loud and with a terrible resonant vibration which totally killed the enjoyment of driving the car. Unfortunately the design was poor in so far as it was far more complicated to remove it and re-install and it still rubbed on the fan and forced the oil filler tube to contact the engine cover. Lastly the helicoil type threads that one of the support brace screws - screws into were sitting proud when delivered and then backed out the first time I undid that screw thus rendering a loose connection at the air filter end and no doubt contributing to the vibration/resonance that emanated from the back end at various points in the RPM range.

After that experience I was very appreciative of the stock air box characteristics so I have elected to simply use a high flow filter (K&N) and remove the Hemholtz resonator which tends to block off part of the filter surface. Most people replace the intake pipe with an aftermarket silicone hose and I will do that when they come down in price to 10 quid but I'll be damned if I'm going to pay 50 quid for an aftermarket silicone hose so I have retained the stock intake pipe and it is clamped to the fitting which I installed in place of the Hemholtz resonator. Credit to GT-4 at UK911.com for identifying that a 1.5" PVC threaded straight tank connector (with nut, poly washers and cap) will serve as a a good block off arrangement for the hole which is left when the Hemholtz resonator is removed. I trimmed about 7mm off the end of the straight tank connector and glued the cap in place.


Transmission & shift mechanism  Dec 2010 Back to top of page

   Whilst the IMS was being done the transmission was off the car so that was the perfect time to do a clutch job and possibly also a replacement flywheel as the Porsche Dual Mass Flywheel (DMF) can be pretty well out of spec by 70-100K. Mine was serviceable in accordance with the TSB so I did not replace it. I did consider a light weight flywheel but decided to stick with the DMF because it has a rubber component to it which is designed to absorb some drive train shock and engine vibration. So much so that the clutch friction plate doesn't have springs (as they would be redundant with the DMF). Hence a solid lightweight flywheel with a solid clutch disk generally results in noise at low/idle rpms and a bit more shock during clutch take up - not something I need in a daily driver.

Tranny rebuild Link (Rennlist):

Dec 2010: Transmission wise to keep things nice and slick, I replaced the original transmission oil with some Swepco 201 gear oil (80W90) due to the well reported  characteristics of that gear oil amongst the Air cooled Porsche community. This is a non synthetic oil suitable for LSD transmissions.

It has been cold weather since I installed the Swepco 201 and I have found a slight improvement in the shift quality in these cold conditions. Nothing remarkable I might add and the shift into 2nd when cold is still somewhat stiff.

14 Jan 2011: After running the Swepco 201 for a couple of weeks and wanting to know if there is anything better I swapped it out for some Mobil SHC (sold in the US as Delvac). SHC data sheets don't say that its is suitable for LSDs and that was a concern for me since I do have an LSD. I contacted various owners and workshops to get their views and established that the GT3 community is very happy with SHC but it's important to understand that the GT3 gearbox and LSD differs from the carrera gear box/LSD. I was advised by a reputable shop to use the SHC without additional friction modifiers for the LSD and I ascertained that reputable shops were using SHC in regular street driven 996 carreras (with LSDs) with no adverse wear or effects. The pump I used was a £6 item from Ebay that can put 500ml of oil at a time into the transaxle and it worked a treat.

Conclusion:  My first impression is that there is a slight improvement in the shift quality using the Mobilube SHC vs the Swepco 201. The SHC is certainly less viscous than the 201 and that may account for some better cold weather shifting. I am happy to say that I haven't found there to be any LSD issues or noises.

996 C2 Factory Spec is 75W90, Capacity 2.7L

Factory Gear Oil - > Shell Transaxle.

Options (Shell transaxle, Swepco 210 & ATF 714 blend, Delvac (Mobilube SHC), Redline 75W90NS Synthetic )

General transmission info at Lufteknic

Delvac (Mobil SHC) info at Lufteknic       

Mobil SHC Datasheet

3 Jan 2011 The 6 speed box on the car feels pretty good yet  many 996 owners find that a short shift kit (SSK) is a nice  improvement. Options include a B&M shifter, a Porsche copy of the B&M shifter, an Ebay copy of the B&M shifter or the 997 SSK. I chose to go with one of the Ebay copies of the B&M shifter because it appears well made and costs 20% of what the B&M shifter does. 

I did also buy a Schnell billet aluminium & delrin shift linkage to replace the factory plastic piece but I elected not to install it as I suspect it offers more problems than benefits. The problem I foresee is that the schnell unit will not maintain a positive grip on the shift cable end and when it moves the shifting will be adversely and noticeably effected.

a b c d e f B&M SSK installation Instructions  

 The B&M instructions are pretty good but I did come across a couple of things that are worthy of mention during the installation.

For a start the lever in the new shifter was installed back to front i.e. it tilted the wrong way as can be seen in the first pic above so I had to remove it and flip it around which was no big deal, it also gave me the chance to apply some silicone grease to the nylon shims and I discovered that the lever incorporates a set of needle bearings, so that's all good. The Ebay item also included a grub screw and locknut for both bushings - only one of these is needed to adjust the end play - I did not install the second one.

The next issue I noticed related to the two blue bushings (end caps), once installed the grooves for both the retaining clips should be visible so that the clips can be installed and prevent the bushings from sliding out. I found that with the bushings installed only one of the two grooves was visible (pic b). To overcome this issue I tapped out the plastic liner (item bb in the installation instructions) and removed the washer from the rearward bushing (see item cc in step 28 of the installation instructions). The washer is only there to spread the load from a rear grub screw if installed (and it  isn't installed). That provided an extra 1mm of clearance. With the shifter out of the housing I positioned both assembled bushings (minus the 1 washer) on the shifter and then lightly tapped them on with rubber mallet to ensure that the plastic liners were fully bottomed into the bushings. This provided adequate clearance and when re-installed both grooves were visible (pic c) and able to have retaining clips installed.

Pic e shows the difference in construction between the stock and aftermarket part and you can see where the different pivot points effect leverage and throw length.

When it comes to adjusting the cables I would suggest fitting the cable in various positions and seeing how the shift feels. In some positions it feels like the gear selection hasn't been completed. You can drive the car without the console installed and I think it pays to do so. It's probably also worth doing with the car cold as well as warmed up. From pic E it can also be seen that the stock shifter has the ball end of the lever bent forwards compared to the B&M style so I suspect that installing the B&M style with the cable in the exact same position will in effect tilt the gear knob backwards a tad compared to stock.

The shift definitely takes more effort but does feel considerably shorter and I imagine it's one of those things that you adapt to after a short while.


Jan 2012 997 Short Shift Kit: Over the past year I have heard some positive things about the 997 SSK and an opportunity arose to fit & try one. Having done so I found it to be a little easier to shift than the Ebay unit but it does have a slightly longer throw. I decided to buy this SSK and leave it installed so that I can try it at the track and see if it can help to reduce the occasional mis shifts that I experienced in 2011.


Suspension   Back to top of page

16 DEC 2010.  I've been debating the suspension choice for the car ever since day one. The options in my mind were M030 (super value/mild) X-74 (good value/good for track/very low/non adjustable) KW-variant 3 (reportedly excellent performance/but higher cost /adjustable/also requires sway bars (+$$) around £2800 in total).  My preferred choice would have been KW V3 with GT3 sway bars and modified drop links. I liked that option because it gave me performance and adjustability. The adjustability was very important, not just for getting it set up right but also because I have to deal with some MAJOR speed bumps in my street. The X-74 with its low height and lack of adjustability was highly desirable as a factory tuned setup with a  good track reputation but simply not an option given the constraints of where I live (speed bumps). Given my budget was getting tight after wasting a bunch of money on gear that doesn't live up to expectations (Fabspeed CAI and Maxflow mufflers) plus the odd un expected expense of £1300 or so for bolt extraction and block welding, I elected to go with the M030 option since it is a decent setup to begin with and mild enough for the street, is very good value  but most importantly, it is not so low that I will have clearance issues with daily driving the car. I've concluded that I will track the car with it's M030 suspension whilst I am in the UK and if I decide to keep tracking it in Australia I'll revisit the choices for track suspension at that time.


M030 kit as supplied:


Stabiliser Front 996 333 701 26

Bushings rear  996 333 792 25

Stabiliser Rear 996 343 701 21 19.8mm

Bushings front  996 343 792 12

Springs front 996 343 531 19 504

Springs rear 996 333 531 26 504

Shocks front 996 343 041 21

Shocks rear 996 333 051 34

Bump stops 996 333 105 03


I compared rear spring length for the old & new springs and the M030 springs were 20mm shorter, but since they are stiffer I'll be interested to see how the ride height compares to my old springs which probably had a bit of settling given they were 12 years old.

As can be seen from the pic the drop link which was bent when I purchased the car has subsequently snapped. So when I swap out the stock suspension for the M030 suspension I will definitely be expecting some improvement in front anti-roll performance!


A couple of notes on this job - The Front drop link upper bolt that locks the front strut into the spindle was seized  in place by that white powdery corrosion that is often seen between steel bolts and aluminium parts.  It took a combination of heat, penetrating oil and hammering to extract the bolt and it was a time consuming job. I was also unable to get the nut off the front struts using the tools I had. My local workshop tried a torch and impact wrench to no avail (destroying the rubber section of the upper mount in the process - see pic to right) so in the end it was a case of having to grip the shaft (ruining the strut) and use an impact wrench to get the nut off. As a consequence I'll be replacing the upper mounts £136 for the pair and the bearings (This was purely elective but done since the bearings can be a source of suspension noise as they dry up ). Underneath the plastic bearing there is a metal piece that mates the bearing to a rubber piece which contacts the spring. I almost neglected to transfer the metal piece to the new strut as it was fused to the old plastic bearing (see pic b to the right). It was only when I was assembling it that I noticed the rubber piece was a loose fit to the bearing and it didn't seem right that there would be no metal load bearer between the spring and the bearing. At that point I retrieved the metal piece from the bottom of the old bearing assembly and put 2 & 2 together. The replacement upper strut mounts are now a 997 part number as per the pics to the right. Ordering the replacement parts is a bit confusing even when looking at the very latest PET in the dealership because the diagram of the strut bearing parts seems to include more pieces than are fitted to the strut (in the case of my car). Suffice it to say that if you ordered part 996 343 515 05 you will get a complete bearing assembly (for MY 99 C2).

M030 Installation (Renntech)

a b c d e

f g h i j

24 Dec The Renntech instructions don't mention removing the front stabilisers (ARBs). To remove them you have to remove 3 of the 4 bolts on the boomerang shaped brace and just slightly loosen the other bolt so that the brace(s) can be rotated out of the way (see last pic). It is also necessary to remove the front bolts for the diagonal braces and loosen the rear bolts so that the diagonal braces can be swung clear (2nd last pic). The other pics show the M030 suspension installed and stabiliser bushings lubricated with silicone grease. Note that (unlike the Renntech instructions) I left the brake calipers attached because I removed the brake lines and replaced them with new hard lines and braided stainless steel lines at the same time as I did the suspension. If you don't want to open the brake lines (& bleed the brakes afterwards), then you need to remove the caliper from the spindle instead.

28 Jan 2011, Emmy doesn't have that many miles on her since I put the M030 suspension on but I have managed to do a number of local drives and a track day at Bedford. I had pre booked a suspension geometry check with Chris at Centre Gravity and today I took the car in to get that check done. The car hadn't been exhibiting any undue suspension noises or untoward suspension behaviour but I wanted the reassurance of knowing that I had a good geometry setup to begin with for 'learning the car' from a track perspective as well as from a general tyre maintenance perspective. Chris wanted to know my intentions for the car and I explained that I used the car as a weekender and I would be tracking the car but that I was not willing to unduly compromise the street driving characteristics to achieve optimum track performance. IE too low was not an option, and rose jointed bushings was not an option. I don't want too harsh a ride or too noisy a ride for the street. I am also going to live with the camber limits available from the stock top mounts & track arms. However I will switch to track tyres & pads once I have gotten a feel for the handling of the 996. My objectives for the car had already dictated the selection of suspension components and engine mounts etc and as such, with M030 and non adjustable sway bars at present, there is a limited amount of adjustability in the suspension ie sway bars are fixed, pre-tension is fixed, ride height is fixed, damping is fixed.


I asked Chris to set maximum front camber to suit track performance and thus I have elected to accept some increased wear for street driving (which I don't do that many miles of) and as Chris explained the increased negative camber will also contribute to accentuating the cars tendency to follow the camber of the road. I thought that was a good point for him to make from an expectations management perspective. Ie be careful what you wish for. So I consciously accepted that and we went ahead. We also discussed the pros and cons of Porsche's factory alignment settings which are a safe compromise for a new 911 street driver but not necessarily as suitable to for someone looking for 'more' out of the cars handling.

 Chris performed a test drive of the car under varying conditions and identified a few handling characteristics that were symptomatic of alignment discrepancies but nothing too major. Likewise there were no significant noises indicating suspension wear problems. We returned to the workshop and began the physical inspection. Chris established that a rear alignment had been done at some point and that the rear lower track control arms appeared to have been replaced at some point - and this was no doubt the reason that the rear arms looked to be in good condition. Further inspection uncovered delamination of the bushing from their installed positions in the front lower track control arms. The delamination was pretty minor and not resulting in any noted effect in handling at this time. Since the deterioration had begun I asked Chris to replace them on the basis that they would eventually result in a handling/noise issue and by having him replace them I would be able to observe the process and learn something. The arms were replaced with 40% cheaper TRW boxed items (TRW makes the arms for Porsche and then grinds off the Porsche Design symbol) as can be seen in the 5th pic above. I was pleased to see Chris goes to extra efforts to make things last (just like I do!) by using lubricants, waxes and sealants that your average mechanic typically wouldn't bother with.

A can be seen from the pics above the car was weighted to my specific weight in the drivers seat and the car otherwise in track trim before the Geo was carried out so that the geometry is correct for me as it would be on a track day.

Chris really took his time to get the settings spot on and explain what he was doing in the process. I have aligned 944s before but not a 911 so I valued the lessons I learned and I came away much better informed about the car. The post alignment test drive went well - since my car was actually in pretty good shape to start with I have to be honest and say that the post adjustment test drive wasn't an "OMG it's fixed!" type experience. However on the way home to Lincoln I had a couple of hours to get a feel for the car and I did come to realise that the car was simply more settled. less fidgety and more consistent in its response. I will be looking forwards to seeing how she goes at Silverstone next weekend.


30 Jan 2011 -  North Weald: Understeer city ?, Well it's been an interesting couple of days! On Thursday I had the car aligned by Chris at CG and in the post alignment test the 996 got around the test roundabout at 29mph before   understeering - this was a very satisfactory result and showed that the car had good cornering ability and when it did approach the grip limit it understeered rather than oversteered - just as it had been set up to do. Then on the Saturday I changed wheels and put on my track wheels so I went from 225 Michelin PS2 and 265 Contis to 225 Michelin PS and and 285 Michelin PS2. ie 40mm extra rubber out back and probably a bit of difference in grip characteristics as well. Tyre pressures were 36/44 for both configurations. Unfortunately this change made a HUGE of difference to handling. I took the car to a driver training session at North Weald with Andy Walsh (Renowned UK Lotus race driver) the next day and the car was an understeering pig. It's still a bit new to me so I'm thinking it must be just me but when he jumped in and put it to the test in the cornering exercise (grip limit test) he was shocked at how badly it was understeering - so badly in fact that he had me change cars into his own boxster so that he could achieve the objective of the exercise which was to give me a feel for how to deal with an oversteer (the boxster was still set up with an understeer bias). It was very telling because I had been through the corner a dozen times in the 996, understeering every time with no hint of oversteer yet on the first run through the corner in the boxster at speed it exhibited oversteer and  spun it. So it became apparent that the tyre change I had made to the 996 had increased traction at the rear and changed the (desired) slight understeer bias into a complete understeer pig. This understeer wasn't really evident in street driving but was going to cost me heavily at the track because I was going to have to get very slow to take the corners and be very late getting on the throttle to exit corners. So consider this as a couple of free lessons - the 996 can exhibit a TON of grip in the rear with zero tendency to step out into oversteer if that's how you like it. Also - changes in tyre width, pressure, brand and age can make a huge difference to the understeer/oversteer bias of the car and the experience of the last couple of days couldn't have made that more clear.

So - what do I do now... I plan to track the car so I will be experimenting with tyre widths, brands and compounds etc. That means I will be getting different amounts of grip front & rear and I need to be able to compensate for that. I plan to keep my alignment/geometry exactly as Chris at CG has set it up for the near term and I will compensate for my tyre choices by swapping my rear sway bar for a GT-3 sway bar which is adjustable. Right now with the track wheels fitted I need the rear sway bar to be stiffer to dial out understeer. When these tyres are done I will probably put 245s up front and with extra grip there I will no doubt have to soften the rear sway bar to compensate. When I move to MPSC track tyres they are available in 235/275 so the sway bar will need to be set somewhere in the middle.  The point of this is that I need some adjustability to compensate for the variations (in tyres & grip) that I am injecting. I should point out that I could play with tyre pressures to affect the oversteer/understeer bias but I like to be able to keep tyre pressures near to factory settings and achieve close to neutral handling before playing with tyre pressures. Once that is done then I can use tyre pressures to fine tune handling on the day. 

For information on how to affect the oversteer/understeer bias see this page General Suspension Tuning Notes


3 Feb 2011 GT3 Sway bar upgrade.    

GT3 front: 26.7, rear: 20.8 (Rear 996.333.701.90)
ROW M030: front: 23.6, rear: 19.6
OEM: front: 23.1, rear: 18.5

So I have elected to go with an adjustable GT3 rear sway bar to correct my understeer issues. The GT3 is both stiffer and adjustable. The pics show the GT3 bar in comparison to the stock bar. As can be seen from the pics the stock bar has the drop link holes in the same position as the softest setting of the GT3 bar (The holes furthest from the bar equate to the softest setting - so attaching the drop links to the holes closer to the bar results in the bar providing more roll resistance ie stiffer) Even though the stock bar holes equate to the softest position of the GT3 bar the GT3 bar is thicker to begin with so even the softest setting is stiffer than the stock bar or m030 bar. The ROW GT3 rear bar uses the standard drop links and new bushings. I have not ordered a front GT3 bar because it is clearly un warranted (ie making the front any stiffer would exacerbate the understeer problem) I will retain the non adjustable M030 bar in the front.

Considering my car had good handling (slight understeer bias) with 225/265  tyres and the m030 rear bar I expect that the GT3 bar on the softest setting  with the 225/265 tyres will shift the bias slightly more towards neutral and I expect to make minor adjustments to tyre pressure (ie drop rear tyre pressures slightly) to shift the bias back towards a slight understeer.

With the 225/285 tyre combination the tyre pressures can remain at stock 36/44 PSI and I will stiffen the bar until the understeer is reduced from it's current 'excessive' level to 'slight'.

Oct 2011 Suspension Upgrade #2

I have done a year with the M030 suspension now and it has proved very capable through 13 track days and a number of driver training events. I did some fine tuning with sway bars, tyres and pressures to get to a point where I was happy with the handling and everyone who had been in the car has commented on how well composed the car is. British Touring Car / Porsche Carrera Cup champion - Tim Harvey has also driven the car a couple of times now and he also agrees the car handles well so that has been a pretty decent professional endorsement.

In the beginning I hadn't intended to build up my 996 as a track car, I had intended to use it primarily as a street car. However that perspective has changed over the course of 2011 and I have now compromised the "everyday" useability of the car with fixed seats and roll cage. For 2012 I will progress the car further down the route of a track setup by going with some increasingly track oriented suspension which will no doubt create some more everyday issues (being lower) and sacrifice some ride comfort (being stiffer) and result in more noise (using spherical bearings).

I have purchased a set of INTRAX 1K2 adjustable coilovers to install over winter so that they will be ready to go for the 2012 season. INTRAX is a Dutch company and the founder of the company is the same guys who founded Ohlins amongst other companies. They are also the supplier of suspension for Radicals so they have a pretty decent race heritage.

The 1K2 setup allows for wide adjustment range of rebound & compression damping as well as adjustable ride height. The shocks are also modular/upgradeable/rebuildable. So I will lower the car from it's present height in order to lower the centre of gravity. The pics to the right show the suspension that I bought, the trouble is that it is a fast road configuration rather than a track configuration, I have been talking to Intrax and the solution is to send it to them so that they can rebuild the suspension with spring rates and damping to suit my plans for regular track use and limited road use. The support from Intrax has been really good.


INTRAX 1K2 Entry level modular adjustable race suspension

Intrax Rebuild

Nov 2011: after a series of discussions with Niek van Sambeek, the chief suspension engineer at Intrax, I had outlined the current & intended setup of the car and how I was using it i.e mainly for driving to & from the track and not so much daily driving. We discussed the types of track that I drive at and my personal preferences for performance vs comfort. With all that in mind Niek concluded that it would be worthwhile building my 1K2s to the same spring rates & damping setup that they use successfully in their 4 Way adjustable race suspension when configuring it for the Nordschleife. This setup is a bit stiffer in the rear than a KW Clubsport setup (approx 1050 inch/lbs) and a tad softer in the front. The rear setup utilises a low rate helper spring  to ensure the primary spring remains seated under rebound but also to to provide a lower spring rate for the car to ride more comfortably over minor road imperfections.

Whilst the suspension was off being rebuilt in the Netherlands I asked them to put it back together with a monoball rear top mount to eliminate any play in that component.

INTRAX suspension rebuilt to Nordschleife road race specs.

Intrax Installation

20 Nov 2011: Whist the installation was fairly straight forwards there were a couple of points worthy of note:

Rears: I installed the rear dampers first and I found that the plastic spacers on the lower mounts were actually about 0.5mm wider than the mounting point on the wheel carrier. Some sanding corrected that issue. There was also some binding when I attempted to pass the bolt through the lower mounting point. A few passes with a round file were needed before the bolt would slide through cleanly.

Something I discovered later was that there was (initially no clearance between the rear GT3 sway bar and the toe arm once the drop links were attached from the rear sway bar to the mounts on the bottom of the struts. With a bit of driving this problem seems to have corrected itself although there are only a few mm of clearance. It appears that the drop link mounts could do with being lower down on the strut body. This would be better of being set whilst the damper is not attached to the car because with the damper mounted it looks like the drop link mount can not be wound down the damper body without interfering with the drive axle. The mount is also tough to adjust because it is secured with medium strength Loctite and the supplied adjustment wrenches for the spring perches are too big to use on the lock ring for the drop link mount. Intrax advised to heat the drop link mount with a hot air gun/hair dryer to assist with braking the loctite bond then adjusting the mount further down the body. There is scope to move it up to 20mm lower than the position it was in when delivered to me.

I thought I'd have a hard time reaching the adjustment knobs with the cage in place but I have found I can reach back there without too much difficulty although I do have to set the camera to one side.

Fronts:  The front struts measured 51.8 mm in diameter and have no metal fin to go in the wheel carrier clamping collar. The OEM struts measured 51.5 and they do have a 2mm fin/tab that goes into the collar. To install the strut I had to clean out the accumulated oxides from the collar with a bit of light sanding and then I had to drive a small wedge (ball joint U shaped pry bar) into the gap in the collar to open it up so I could slide the damper in place. The damper sits with the adjustment knob quite close to the coffin arm ball joint nut but it does not interfere. I had a concern that it would be possible to over-tighten the clamping collar on the strut since the Intrax strut has no metal fin to fill the void in the collar. This proved to be correct as I discovered when I raised the car after the install and noticed that the front wheels had not gone into droop, they were still up in the wheel arch as if the car was on the ground. As soon as I loosened the drop link nut which tightens the collar the strut extended and the wheel went into the expected droop/rebound position. Intrax advised to only tighten the nut to 50NM but that is actually tighter than I had set it at when I experienced the restricted strut travel. So I have been experimenting with some shims in the collar gap so that the collar cant be over-tightened. With 4mm shims the collar can still be over tightened and restrict the travel of the damper piston so I'm going to try a 5mm shim

The mounting studs were supplied with some rather small standard nuts which would have had little hope of keeping the strut clamped in position at the desired point along the slot. I therefore decided to use the Porsche OEM nuts which have an extended base. Unfortunately these nuts are also a type of deformed locknut which ended up chewing up the thread on 2 of the studs and snapping one of them as can be seen in the last pic. That being the case I have replaced all the nuts with stainless steel metric flange nuts as a compromise.

Camber Setup.

The front camber plate needs to be adjusted before the strut is bolted in because the six locking screws are not accessible once the strut is in place. The first pic of the camber plate shows that there is one hole visible at each end of the row of locking screws. With the camber plate set that way I was able to obtain about 1.5 degrees of camber when the strut was pushed inboard as far as the OEM slots would allow. I then elongated the hole at the top of the strut tower into an egg shape and re-adjusted the camber plate screws until they were ALMOST at the end of the slots (DON'T put them fully to the end of the slots or the silver/circular bearing mount will protrude past the edge of the stud recess on the underside of the camber plate and you will not be able to insert the stud when installing the strut. Ask me  how I know. Leave a small gap of a few mm as per the second camber plate pic). With the camber plate set this way and with 6-7mm ground away at the strut tower, I was able to set up to approximately -2.3 degrees of camber.

Spring compressors - Not used during M030 removal or Intrax install.

The 1K2 system as built for me weighs 20.0kg. The M030 dampers with top mounts weigh: 22.2kg

Intrax Steel Strut Bodies

Dec 2011: My initial testing of the Intrax dampers established that there was an issue with the (front) damper travel being restricted by the wheel carrier pinching the aluminium strut body. This was first evident by the wheel remaining in the up/bump position even when I raised the car on the lift. As soon as I loosened the wheel carrier pinch bolt the damper extended into the rebound position as would be expected. On the road this problem manifested as a harsh/juddering ride even with the damping on full soft. When I flagged this issue to Intrax they sent me a set of steel strut bodies to replace the aluminium bodies. The steel bodies weigh an additional 500g over the aluminium bodies but they have successfully eliminated the initial issues I experienced. The steel bodies are also a fraction shorter than the aluminium bodies which means there is more clearance between the adjuster valve and the lower coffin arm.

Street Driving Impressions Jan 2012

With the steel strut bodies installed the dampers are now operating correctly and I have been able to do a number of test drives on the local patchy/bumpy/uneven pot holed Lincolnshire back roads. Considering the spring rates are 570lbs/inch front and 1254 lbs/inch rear, I am genuinely & pleasantly surprised to say that the ride comfort (with damping set to minimum) is completely acceptable even on the poor roads in my area. The handling is also very good even with this soft damping set. I was a bit worried how driveable the car would be on local roads with these very high rear spring rates but it seems Intrax were correct when they said these dampers would remain street driveable.

The dampers I bought were new but had been on someone shelf for a while and when the steel strut bodies were delivered we realised that the damper design had changed slightly (bigger piston rod) so I called Intrax and then I had to bore out the hole at the end of the strut body to 14mm to suit the dampers. That was a minor delay but no big deal. It was also an interesting opportunity to see the strut internals (Inverted damper design) and note the bump-stop contained within the strut body.

Suspension clunking/rattle Jul 2012

July  2012: xxx


Rear Monoball Toe Arms.

Jan  2012: In order to minimise toe change under load I have replaced the OEM rubber bush rear toe link with an RSS bumpsteer adjustable monoball toe link. This has  also be installed with an RSS locking plate in place of the toe eccentric which has a reputation for shifting under load and degrading the alignment. The use of a monoball design eliminates toe changes and delivers improved consistency in the cars handling under significant corner loading.

Geometry & Corner balance

Jan  2012: The car has been back to Centre Gravity where Chris spent the entire day on the car preparing for the upcoming track season. The rear toe control arms were installed along with the locking plates and a basic corner balance performed prior to the geometry being set. Once the track alignment was completed the fine adjustments to the corner balance were completed. The resulting weight of the car is 1325kg with 1/2 tank fuel. and a perfect 50% load across the diagonals. The only thing I would have liked different is for the car to be a fraction lower in the rear but we stopped at 130mm rear height because if the adjuster had been wound any lower the pax rear spring would unseat under rebound.

The test drive under freezing conditions showed that the car has lovely progressive handling and the damping is well designed to manage the high rear spring rates without being overdone.

Feb 2012:  I've put in 3 trackdays already (Oulton, Snetterton & Silverstone) and I couldn't be happier with the suspension. I'm loving the ability to adjust the damping and consequent grip to suit the conditions and then back it off for a comfortable drive home. It was a bit of a leap of faith to go with this suspension since there was limited feedback about these dampers but any concerns I had have now been put at ease.

Rear Control Arms.

Oct 2011: In addition to stiffer springs & damping I am also attempting to eliminate some of the suspension changes attributable to compression of the rubber suspension components. With that in mind I have picked up a set of standard control arms that have already been modified with GMG Racing monoball bearings at the inner arm link and with GMG adjustable billet castor pucks.


Porsche 996 Limited Slip Differential LSD / Traction Control.

  My 996 is one of the rarer ones fitted with a GKN manufactured Option 220-Locking Differential 22/40% (ie 22% LSD locking under acceleration & 40% locking under braking), Option 222 Traction Control System and Option 224 Automatic Limited Slip Differential. The car runs ABS 5.3 and is not fitted with PSM. Whilst the LSD is a much more desirable option for the track than the open LSD fitted to most 996 carreras, the Option 220 LSD is not particularly aggressive in its lockup rates compared to the GT2&3/Motorsports LSDs which use lock up rates of 40/65%. As has been discovered by the GT3 track fraternity the non motorsport 996/997 LSDs also have a history of not functioning effectively for very long due to the friction material Porsche used. The good news is that all the 996 LSDs can benefit from the very effective Porsche cup/motorsport friction disk it. Matt Monson at Guard Transmissions in the US has also developed aftermarket friction discs and ramps for these LSDs As my C2 LSD basically uses the same LSD body as the GT3 & Motorsport LSD, it can be rebuilt with the aftermarket ramps from Guard Transmission to give it a locking rate of 40/60% which is a more aggressive rate better suited to the track. Matt also confirmed that the C2 LSD does use machined gears rather than the cast gears employed in later 997 GT3/RS LSDs. I have also discussed my rebuild options with Steve McHale at JZM in the UK and may have JZM rebuild it. The Porsche cup rebuild kit provides about 60-70nm of pre-load. At the moment there is next to no preload on my car. With my car raised and me turning one rear wheel  my clutch based LSD should result in the other wheel turning the same  direction but in fact nothing at all happens and it takes very little effort to rotate the wheel by hand (i.e. the is little pre-load resistance).

Note 1: Option X75 and 911 Anniversary model cars were fitted with a 22/27% LSD compatible with PSM.

Note 2: These friction plate LSDs are superior to TORSEN gear based LSDs for track work because the friction plate LSDs provide the lockup under braking which significantly  improves the back end stability of the car under heavy braking from high speed.

OEM Traction control system (this is a summary of it for my own reference!) - The LSD mechanically transfers engine torque from a slipping wheel to the wheel with traction in the traditional way. Option 224 uses the ABS system to create a virtual brake LSD system (rear axle only) but this 'brake differential' only operates on the rear wheel which has lost traction when the vehicle speed is below about 62mph. Above that speed the Option 222 part of the equation will begin to reduce the amount of fuel injected and also retard the ignition timing to reduce the amount of torque that the engine develops until traction is regained at both rear wheels ie it cuts power to eliminate wheel spin. The option 222 & 224 traction control effects can be turned off by pressing the traction control button on the dash and the TC effects will stay off until the car is re-started. Turning of TC for track work thus prevents the cars onboard systems from interfering with balance/conditions the driver may be trying to invoke. Since the TC system employs braking on the wheels and reduction in engine output it is also probably going to be slowing you down rather than helping to exit corners - hence it gets turned off at the track.

These behaviours are quite different to that which PSM delivers (no physical LSD, 4 wheel independent braking, and PSM which re-activates under certain conditions after it has been turned off).

* Pics from GT.



GT Friction discs vs OEM GT3 brass discs & GT ramps

LSD in a 911 - good background info:

Over the past month or so I have done of lot of reading and talking to people about LSDs in order to improve my own understanding of how they function, what my rebuild options are and what the pros & cons are. It's been a pretty interesting time and I have learned quite a lot. Of course there are varying opinions out there about the need for / benefits of an LSD but what follows is based on what seemed to me to be the consensus opinion of the people who have gone down the path of an upgraded LSD & or the recognised experts in the field. I thought it might be handy to summarise some of those  points here:

Track cars do benefit from being fitted with a clutch type LSD (over a TORSEN LSD), they deliver increased braking stability, especially at high speed and during trail braking into corner entry and increased corner exit speed by allowing you to get on the gas earlier without wheel spin post apex. Saving 3 seconds or so at a track with a 2 minute lap time is the type of improvement noted by a GT3RS driver who went down the path up upgrading from the factory GT3RS brass plate LSD.

A decent clutch LSD should last several years (3-4) of use for someone that does regular track days.

40/60 is a good compromise rate for a serious 911 track car that still sees street use. 50/80 plus starts to create understeer/oversteer issues that demand significant adjustability in the rest of the suspension system in order to restore suitable balance/driveability. High ramp rates will have more pronounced effects in tight 2nd gear corners when the LSD will lock, deliver extra rear grip and create understeer if the front suspension setup isn't able to be configured to match that extra rear grip. In a street car similar untoward effects may be observed when performing tight turns during low speed domestic manoeuvering. Overdoing the ramp rates beyond 40/60 or 50/80 can thus have detrimental effects on the cars agility in corners.

Belleville washers are a well established way to deliver pre-load to the clutch/discs and this arrangement is more tolerant of wear so it is a fundamentally sound approach to building an LSD. Porsche's move away from Belleville washers (and use of brass based friction plates) in recent years has resulted in their LSDs being considerably less effective and more short lived and that approach appears to have been indicative of Porsche's need to cater more to the average street driven car/driver rather than the performance expectations of the considerably smaller track day crowd. In other words recent Porsche LSDs have sacrificed track functionality in favour of traction control that has been achieved through other braking or engine torque management effects which are detrimental to lap times because of their braking effects and engine torque reduction effects but are inherently cheaper to deliver since the multi channel ABS  systems and ECU management of the engine is already in place whereas an LSD is a mechanical item which represents additional cost, weight & it is a wear/maintenance item which non track enthusiasts may consider undesireable.

The use of 8 disc clutches (as in cup cars) vs 4 disc clutches does not seem to offer increased benefits to a typical weekend track car (whereas it is possibly more important to an  endurance full on race car), but 8 disc clutches do increase cost.

OEM clutch discs based on the brass material can only tolerate about 0.1mm of wear before becoming ineffective, the Guards discs with Belleville washer preloading can wear up to about 0.4-0.5mm before they become ineffective. The Porsche motorsports non brass friction discs have a reputation for good longevity as do the guards discs.

Pre-load of around 60lbs is what Guards recommend for a street driven track car, the motorsport internals in a GT3 diff are about the same. By comparison a cup car with an 8 plate clutch will have about 120ft/lbs preload - but this is in a cup car that may have to endure a 24hr endurance event and with suspension/tyres to match.

The preload is set by choosing a Belleville washer of a given height and thickness to suit/match the assembled height of the rest of the friction and plain discs which form the clutch stack.

A Belleville washer is just like a flat washer that has been pressed into a bit of a cone shape, it is basically a simple/durable/effective spring. One of the pics to the right shows a Belleville washer next to a plain plate.

The diff spends most of its time unlocked - the 40 in a 40/65 diff means that the wheels can experience 60% difference in torque before the LSD will lock, Under braking the 65 means that only 35% difference in torque between the rear wheels will be tolerated before the LSD locks... and when it locks both wheels will turn at the same rate. When both rear wheels lock to rotate at the same speed, going around corners becomes more difficult - the car may become less nimble if the rest of the suspension cant deliver traction where it is needed.

LSD Links (from where a lot of the above was originally gleaned.)  Link 1 Cayman LSD  Link 2 LSD Buster 6Spd online  Link 3 LSD Buster Rennlist Link Vintage differential video (Excellent)  Link 911UK re LSD Buster Link Wiki


996 Carrera LSD Rebuild Nov 2011


Polished plates     2.5mm x2

Dull plates           2.33mm x2

Friction plates      2.08-2.2mm x4

Bellevile washer    1.85mm / crown height 4.6mm x2

Ramp cup 35.05mm total height or 26.06mm between base and crest of divot

Plate diameter      98mm

Annulus               20mm

Stack height (no gears) without Belleville washers 88.73mm

Polished plates     2.5mm x2

Here are the pics of the LSD being removed from the car.

LSD removal process

With the car raised and the rear wheels removed, drain the transaxle, apply the park brake, put the car in gear, undo the CV joint bolts at the Transaxle on both sides. I release the brake and rotate a pair of bolts to the top position and then apply brake, undo them etc. Once the CV joints are undone, install two of the bolts into the stub axle and counterhold the stub axle with a crow bar whilst you undo the bolt in the middle of the stub axle, withdraw the stub axle. Repeat process for the other stub axle. Undo the 11 LSD cover plate bolts then tap the cover plate free from the transaxle by using a light mallet & wooden block against the purpose built webs on the lower portion of the cover plate. Catch any residual oil as the cover plate comes away. The LSD can then be manoeuvered out of its housing - it can be a bit awkward with the CV joint in the way but nothing too bad. The LSD with ring gear weighs approximately 30lbs though so be prepared for that weight.

Below are the pics of the LSD being disassembled, I was fortunate enough to be able to work with my Indy at his workshop to do the LSD rebuild. The 12 bolts buzzed off easily, and surprisingly the ring gear was tapped off easily with a nylon mallet.

Below are the pics of the LSD going back together with a liberal coating of gear oil, I ended up doing this twice because I made the mistake of installing the parts into the housing when the parts should be built onto the end plate. With the parts assembled on the end plate the numbers adjacent to the ramps on the GT ramps, will be on the left hand side. By installing the parts into cover with the numbers to the left (as I did it the first time) the ramps are actually backwards, as well as being plain wrong this also showed up as an excessive pre-load (150ft/lbs). With the parts reinstalled correctly the pre-load measured 62ft/lbs - right on target. The second pic below shows how the belleville washers make the end plate sit proud and it is necessary to squeeze the halves together with vice grips when installing (or removing) the 3 screws. That squeeze is the pre-load which is squeezing the friction discs against their mating surfaces. The ring gear bolts were tightened to 75 ft/lbs initially after having loctite applied, they were then tightened to 140ft/lbs in an alternating pattern. I had to counter hold the LSD in place with a pry bar between a pair of the bolt heads whilst the other bolts were torqued up - otherwise the LSD would turn in the vice. The last pic shows a fitting that allowed the pre-load toque to be measured with a torque wrench, Matt at GT said a more realistic preload setting is obtained after the LSD has been through about 5 heat cycles.

Below are the OEM parts that were in my LSD  only 2 friction discs ie 1 per side. They are carbon based, same as the 993T discs. It appears from the markings on the ramps that the ramps may also be 993 origin 25/65 ramps rather than 996 22/40 ramps as expected. The last pic in this serios shows the friction disc, the disc is 2.68mm thick at this point and after many attempts I finally got a pic that shows the wear tends to occur one one side rather than both sides. Advice from GT suggests that the components in this LSD probably had an effective life of about 20,000miles.

Below - LSD ready to go back in the car and back in the car. I found it helpful to use the stub axle to get the LSD back into its cavity and mated to the pinion gear. I then put the stub axle through the transmission cover and used the stub axle as a means of lining up the cover plate bearing race to the LSD and the transaxle body simultaneously - that seemed to work pretty well. I replaced the corroded OEM bolts with stainless M8x35 flange bolts and they get tightened in an alternating pattern to 24N/m.


Click the above image for a full sized view which shows the clutch components & ramps stacked as they will be installed into the LSD housing (as per an LSD oriented with the pinion gear side towards the bottom - like the above left pic with the LSD on the vise)

Note 1 the Belleville washers can be installed inverted if desired.

Note 2 Some diffs (ie Cayman) come from Porsche with the friction plates adjacent to one another rather than interleaved!

These are the components that make up the clutches.


Belleville washer (spring)- thickness and height determine the pre-load applied to the clutches.

There is a given amount of depth or space within the LSD housing so the thickness of the discs and plain plates is chosen to fit the assembled stack within the housing with a bit of space and then a pair of belleville washers of suitable height and thickness are chosen to deliver the desired amount of spring force/pre-load which will come into effect as the two portions of the LSD housing are bolted back together


Street Driving Impressions Jan 2012

I wasn't expecting to be in a position to provide driving impressions about the LSD until I got some track time with it. However it turns out that the effects of the working LSD can be felt in normal street driving  at perfectly normal legal driving speeds as well.  Pulling away from tight corners the LSD can be felt biting in such that the applied level of throttle seems to be delivering more punch. When driving the car through corners at anything resembling a sporty pace the car simply feels more grippy and planted where before it would have felt there was some slip and an inclination to be tentative with the throttle. 

There is a varying engine note that I have regularly heard at the track when I have watched race cars accelerate out of the pit lane to joint the circuit. It can be heard in street cars as well but not so distinctively, now with the LSD working I noticed this effect much more than before and I realised it's the LSD reducing tyre slip under straight line acceleration and thus putting more load on the engine as the car accelerates away.

996 Cup Splitter

Since  I'm in the process of giving the car a greater track focus I've  gone ahead with a more aggressive front splitter. So I have ditched the standard splitter and chosen the Cup splitter rather than the GT3RS splitter. The splitter is designed for the MkII cars but can be easily adapted to the pre facelift cars. The modification requires cutting off the ends as per the attached pic (Hacksaw). The front centre mounting hole lines up with the original front centre mounting hole in the bumper but the rest of the holes do not. So I put the splitter in place with the single front plastic rivet, then I drilled through the splitter making a 4mm ish hole at the end as can be seen in the 2nd pic to the right. You can then unscrew the existing screw which secures that flap and use a longer screw to secure the flap and the splitter. With the ends and the middle of the splitter secured you can mark and drill the remaining holes and then install the plastic rivets to firmly fix the splitter. I initially installed the splitter without the double sided tape but will refit it with the tape and some silicone to ensure it remains secure at speed with no gap.

The splitter will provide some additional front downforce at speed, hopefully that will be noticeable in Craner curves at Donny.

May 2012:  I put a wheel off on the side of the road on a country lane recently to get around another car. I'm now on my second splitter. :(


Part Number: 996.505.986.91

€175 delivered Carnewal

Cup Steering Wheel  18 Dec 2011

With my track objectives for the car I have replaced the OEM airbag steering wheel with a Momo Model 07 Suede (350mm) steering wheel mounted to a Momo 7004 Hub.  This is basically the same as the cup steering wheel without the Porsche logo on it In addition to the wheel and hub it is necessary to buy a 2.8 Ohm (I used 2.7) resistor to use in place of the airbag and so prevent a warning light being flagged by the ECU, and a plastic/copper elbow ( OEM part number 964.652.104.00) which simply clips into the existing steering column surround to facilitate provision of 12v power to the horn button via the slip ring on the base of the Momo 7004 hub/boss.

This is the procedure I used:

Note 1: power should not be applied via the ignition switch when there is no airbag/no resistor connected to the orange plug - else an ECU Airbag fault will register and require resetting at a service centre.

Note 2: Airbags are pyrotechnic hazards with potentially serious risk of injury. Disconnecting or removing airbags by persons unqualified to do so is hazardous and not recommended.

Note 3 Tampering with or removing the safety systems of a vehicle may increase the risk of injury in an accident and have serious implications for your insurance cover.

Prior to removing the steering wheel ensure the wheels are in the dead ahead position. Disconnect the battery and allow the car to sit for 10 mins. extend the steering wheel towards the driver & rotate the wheel as necessary to access and undo the T30 Torx screws (see pics). Pop the yellow plug off the airbag. Unclip the horn wire connectors from the OEM steering wheel, remove the 24mm nut & washer. mark the steering shaft 'top' position with the steering wheel in a level orientation.  Remove the steering wheel. Remove the 2 screws from the slip ring assembly. Remove the 6 screws securing the plastic trim  for the steering column assembly and remove the 3 pieces of plastic trim. Unclip the red & orange plugs from the slip ring assembly and remove it from the car.

I then cut the red & orange plugs from the airbag assembly and modified them as per the pics, ie a 2.7Ohm resistor was soldered across the wires from the orange plug and I soldered a standard automotive bullet connector (female) to the brown/white white wire from the red plug, I then used needle nose pliers to reduce the size of the plug for a tighter fit on the pin from the elbow.

The Elbow clips into the steering assembly as per the pic. The pin from the elbow is covered by a plastic plug on the back of the steering switch unit. Prise that plug off and then cut/trim it back as per the pics so that the elbow pin is exposed. The modified red/orange plugs can now be connected to their counterparts. This effectively puts the resistor in place of the airbag so the ECU still thinks the airbag is present. The bullet connector is then connected to the elbow pin - make sure it is snug. This connection provides the horn power. The other wire from the red plug does not need to be connected as the horn button will connect to earth through the hub  & steering column when the horn button is pressed. (A good earth may not exist until the steering nut is tightened.) Install the hub/steering boss noting the orientation of the 'top' marker. Counter hold the steering boss with a brace & then tighten the steering nut to 33 ft/lbs. Assemble & wire the horn button as per the pics. Slide on the bellows over the hub and orient it's 'top' marker so that it has a neat fit on the hub. Orient the horn button to be level, position the steering wheel over the horn button and screw it in place with the supplied screws. Reconnect the battery & test the horn.

The weight saving from this installation is 1.6kg.

Reference Links

Rennlist Thread



Ride Heights

OEM stock  RF-66cm LF-66cm  RR-66.5cm LR-67.5cm

Dec 2010 Immediately after installing the M030 and before going for a drive the heights are at 67cm front and 68cm rear. Underside reference points at 133 / 153mm F&R when Geo was done at CG.

26 Nov 2011 With the Intrax suspension installed the ride heights have been set to 64cm at the wheel arches. or using the underside reference points 112/126mm (F/R)




Suspension heights: L to R OEM stock, OEM M030, Intrax



Wheels - 9 Oct 2010 Back to top of page     (Wheel Weights Table with wheel pictures)

<< Oct 2010 This pic is Emmy on her loaner wheels whilst the Sport Classic II's were  away being re-furbished.

I will not be going to 19" wheels even though they look nice as they just make for a compromised ride quality on  the street. Emmy came with Sport Classic II wheels which look great (or they will look great when they get back from the re-furb shop). My only concern with SC II is that they are a complex wheel shape and will be a pain to keep clean. She's wearing turbo twists while the SCII's get refurbished and I have to admit that whilst I have always thought turbo twists are a bit plain, they are simple, and easy to clean and they look alright with a silver car.

08 Oct 2010: To the right are the wheels after being refurbished by Exel wheels (www.exelwheels.co.uk)  Chris at Exel is a Porsche owner himself and knows his wheels. He provides a great service by coming to  your place to fit loaner wheels whilst he takes yours away for a high quality refurbishment. Mine were in very poor condition to begin with so I was pleasantly surprised to see them come back in such pristine condition. Stand by for some better quality pics to highlight the delta between the original and re-furbished condition. I have no hesitation recommending Chris to others who are interested in having their wheels refurbished and I say that without any incentive other than I am very happy with the work that was done and the service that was provided.



Porsche Sport Classic II, 2 piece wheels as photographed on the day I first viewed the car (18 Sep 10) and then again after refurbishing by Excel Wheels.


Track wheels - Jan 2011

I decided I'd like to get a set of track wheels so that I can run some R compound tyres and make better use of some track brake pads so I set about looking for some OEM wheels. I didn't want to spend big $ on aftermarket lightweight wheels so I like OEM wheels for strength/weight & value.  I ended up finding a set of 996 Carrera 5 spoke wheels 8J ET50 & 10J ET65 wearing 225-40ZR18(N1) & 285-30ZR18(N3) Michelin Pilot Sports for use as a set of track wheels. These are in fair  shape but I'll freshen them up and have some Wurths silver wheel paint and clear lacquer on the way. I plan to use these wheels with the road tyres for my first couple of events while I get to know the car and then I'll switch to track tyres.

Feb 2011: I have also been shopping around for track tyres of course and had intended to go with Michelin Pilot Sport Cups but I found a deal on some Toyo R888s that was just too good to pass up so I have ordered them (245/40/ZR18 & 285/30/ZR18). UPDATE: I was a bit to hasty in accepting the 245s up front as I discovered that others who fitted 245s experienced rubbing of the fender liners on partial lock. That being the case I returned them and sourced 235s from Camskill as Tyre Drive didn't have the 235's in stock due to some general shortages of R888s in the UK at the moment.

Specification  Sidewall  Radius  Diameter  Circumference  Revs/Mile  Difference (MPSC Sizes for a Track C2 - ie The size of my latest set of MPSC)
235/40-18         3.7in  12.7in    25.4in         79.8in        794        0.0%
295/30-18         3.5in  12.5in    25.0in         78.4in        808       -1.7%
Specification  Sidewall  Radius  Diameter  Circumference  Revs/Mile  Difference (My Toyo R-888s 2011/12)
235/40-18         3.7in  12.7in    25.4in         79.8in        794        0.0%
285/30-18         3.4in  12.4in    24.7in         77.7in        815       -2.6%
Specification  Sidewall  Radius  Diameter  Circumference  Revs/Mile  Difference (My MPS2s 2011/12)
225/40-18         3.5in  12.5in    25.1in         78.8in        804        0.0%
265/35-18         3.7in  12.7in    25.3in         79.5in        797        0.9%
TYRE Links


R-888 Sizes   MPSC Sizes   Michelin Pilot Super Sport Sizes* not yet in good sizes for Emmy

Standard C2 tyres sizes are as below with a 0.9% radius difference

225/40ZR18  Circumference 78.8"

265/35ZR18 Circumference 79.5"

Radius delta should be <3% to avoid ABS issues related to relative wheel speeds.

Tyre Radius Calculator will enable comparisons of tyre radius for new tyre types.

Wheel clean up

The face of the track wheels looked ok from a few meters away and there was minor kerbing on them but the inside of the wheels had lots of lifting paint and surface pitting/corrosion. Even though they are track wheels I thought I'd clean them up since they'd be an eyesore otherwise. I figured that cleaning them up would also be a good time to mount the tyre pressure monitoring system since the clean-up and TPMS mounting will both effect the balance and I can get them balanced just the once. The clean-up will also give the wheel weights some clean surface to mount to. I thought I'd have a go at cleaning the wheels up myself (Bad idea). I did 95% of one wheel using an 80 grit sanding disc but using that means having to have a very very light touch as it will readily grind away metal (Pic b). The remaining 5% of the wheel is the inner parts of the hub that cant be sanded by wheel or hand and I didn't want to leave an area of metal with corrosion on it as doing so would begin to compromise any painted area adjacent to it. So I carted the wheels into my nearest powder coating workshop and had the wheels blasted (like I should have done in the first place). That cost   £60 to get the tyres dismounted and 4 wheels blasted.

The blasted finish feels rough like sand paper (Pic C) and has to be sanded smooth by hand and I used 280-400 grit for that (Pic D) and I used 120 grit over a spongy sanding pad to re-profile the edges to remove kerbing marks. Each wheel took a good hour or so of sanding. To paint the wheels I suspended the wheel from a roof beam in my garage by passing the strap through the hole where the wheel cap goes. With the wheel at waist height I could spray from above and below and rotate and angle the wheel to get excellent coverage. Pic F shows the wheel primed and allowed to dry for 24 hrs before going over the wheels with a 400 grit sand paper again to smooth the primer in readiness for the paint.  I thought I might not have quite enough Wurths silver wheel paint on hand so I painted the hidden section of the wheel in black and then I have applied the silver to the exposed wheel surfaces.





Tyre Pressure Monitoring System  - Feb 2011:  I've decided to splash out on a TPMS to let me monitor tyre pressure and temperatures live whilst I am on the track. I expect this to be an educational piece of kit for seeing what's going on with my tyre pressures and temps on a lap to lap basis and being able to correlate that with how the handling of the car is changing. This will be far better than what I have been doing until now which is just measuring the tyre pressures when I get back to the pits after the cool down lap. Temperature data will be a bit less useful I think - at least on comparison to measuring temperature in 3 places across the tyre surface to see where exactly the tyre is doing most of its work. So when I get serious about it I'll have to break out the probe pyrometer for that job. I'm curious about how much lead it will take to offset the sensors attached to each valve.

 (TPMS OEM Link)

Torque spec - 4nm +/- 0.5nm for screw and valve body.

UPDATE MAY 2012: Sadly this system has not stood up well. after bringing my wheels out of winter storage it seems that 3 out of 4 TPMS sensors have failed. I went through the procedure of deflating the tyres in setup mode to reinitialise the system but no joy. I've done plenty of driving on them and a couple of  track days and reinitialised them a few times and they still have not come good. I also contacted the OEM for their advice but they didn't bother responding.


 Link for spare valve parts in UK


This bracket from a hardware store proved perfect to mount the TPMS monitor to one face using the velco and the other edge slides nicely into the gap between the console and dash. That means it covers the cd trays which for me is fine as I have never used it. I liked this as it saved me from having to attach and adhesive or fasteners to the dash.

Front Wheel Spacers  - 15 March 2011:  I have installed 15mm front spacers & 15mm longer bolts. With 8J ET50 wheels&  225/40ZR18 Michelin Pilot Sport tyres & M030 suspension, these are not exhibiting any rubbing during normal driving including full steering lock. The front wheels definitely look like a much better fit in the wheel arch. My local country roads are quite poor and make for a good test of wayward suspension characteristics and I am happy to say that the fitment of the spacers has not had any adverse steering effects what so ever, likewise on the A roads. On track the extra front track width will further reduce understeer.


The first two pics are prior to fitment of the spacers and the second two pics are after the spacers have been installed.




Track Wheels - June 2011  update. Team Dynamics Pro Race 1.3

18x8.5 ET 45 (11.0kgs)

18x10.0 ET 65mm (11.75kg)

I have decided to go with a set of brand new designed for the track track wheels. I considered OZ Racing Allegeritas and Team Dynamics Pro Race 1.3s and ended up going with the Team Dynamics wheels on the basis of cost £860 delivered vs £1800 for the Allegeritas in silver. The Allegeritas are impressively light and sorely tempting but I couldn't justify them for my 996 which has the weight and suspension set up of a road car rather than a track car. So in the end I brought the Team Dynamics wheels and a new set of Michelin Pilot sport 2s for my road wheels for less than the cost of the Allegeritas. The other factor that swayed me to the team dynamics wheels was the fact that they are well represented as the wheels on many of the race cars at the track days I have been attending recently. I originally ordered the fronts with an offset of 40mm rather than OEM 52mm but ended up with 45mm offsets (long story). They are mounted with standard wheel bolts which protrude the same distance through the hub as they do when fitted to OEM wheels. The 45mm offset is equivalent to running a 7mm spacer on OEM wheels. I have left the rears with the standard offset as I wish to retain the standard rear track on the car (for the time being at least).

30 Jun 2011: Got the wheels & tyres sorted today  ->

The Pro races are now fitted with Toyo R-888 235/40/ZR18 & 285/30/ZR18  track tyres and TPMS sensors and they seem to have balanced up nicely, overcoming the issues I experienced with my earlier track wheels.


June 2012 Update. I have run these front wheels with 235/40R18 Michelin Pilot Sport Cups and a 7mm spacer (effective offset: 45-7=38mm) at the track and they were fine. Camber was -2.33 degrees but I don't believe that was a big factor in enabling the fit. I did try with a 15mm spacer and a 235/40R-18 Toyo R-888 but the tyre did catch on the fender lip in the 1 o'clock position.


Interior - 12 Oct 2010

Not a whole lot will be done with the interior, although I did opt to replace the standard shifter with a Porsche crested Techart version in silver and black and I put in new OEM floor mats in black as well to provide some contrast to the otherwise grey interior.

(last pic is as purchased)



28 Oct 2010 Coil pack heat shields

Coil pack / cam cover  heat shields - these shields looked terrible on all the cars I have seen in the UK. At 12 quid each they are pretty cheap to replace and it can be done with the standard mufflers still in place too (as I know from doing them on my last 996). There are two of the same part number, and the same part fits either side.


Scissor Lift

A After many years of thinking about getting a lift but having not done so due to reasons of cost / space or re-locatability I have finally found a solution that suits my requirements very well. I can park over this lift and it can be moved about. That means that when I move out the lift can go in a shipping container with the car and be utilised at my next address. The lift was also quite good value especially with a strong Aussie dollar at the moment.

This certainly makes life easier for major maintenance but it also makes things considerably safer compared with traditional car jack methods. Now my track day car preparation is a lot easier and faster as well .... wheel changes, brake bleeds, oil changes... all definitely a lot easier!



Porsche Recaro GT-3 Seats

Originally I had no intention of putting fixed seats in the car because they seriously reduce the useability of the cargo space in the rear and the reality is that space gets used for lugging things on holidays and track days too. However as I am doing more track days than expected I have been on a quest to reduce the weight of the car and more recently I concluded that I wanted to achieve a better driving position by being firmly strapped in (See reference to driving the R300 Caterham). So I looked into seat options. I quickly discovered that seat options can get confusing by the time you decide what brand suits you then what width you need, then what mounts you need, then what sliders you need. then what seat belt mounting arrangement you need. At that point it became clear that the OEM solution using Recaro GT3 seats was attractive for more than just the OEM look factor. Although not a cheap solution it does resolve all of the headaches that can come with a non purpose designed solution. Importantly this solution supports mounting the seat belt receptacle on the slider (as opposed to being fixed to the body). If going aftermarket look at Brey Krause side mounts which also support a mounting of a seat belt receptacle but do your home work because the mounts only suit certain seats. Porsche shop is the UK distributor for BK but once again I had poor service from Porsche shop and they never got back to me when I asked them to get some specific BK parts (before I went with the GT3 seats).

Tequipment Safety Roll Bar

There is a You Tube video (Not by me) for the installation of the Tequipment roll bar. I have added some extra pics to my website to show a few key points. I did not remove the side plates along the bottom of the door frames. As can be seen it is possible to pull back the carpet sufficiently to make the necessary plastic cuts. I had removed the carpet from the rear seat area. This did make the job easier but is probably not necessary.

The roll bar weighs 13kg. plus the weight of the hardware and spacers.

Note that where a GT3 seat is installed with the seat belt running through the seat back holes it is possible to remove the seat from the car with the seatbelt still attached to the roll cage lower mounting point. I did this to access the rear without having to undo the lower mounting bolts for the roll bar. The last pic is the new carpet panels I made for the rear.


Schroth Profi II-6 Porsche Harness

Using the same philosophy of using the OEM solution for the seats, I went with the Schroth Profi II-6 Porsche Harness which is designed with all the right fittings specifically to bolt into a 996/7. From past experience I knew that it can be a hassle mounting a harness safely and correctly and I didn't want to go down that path. I think this is a fair value harness considering it is such a tidy solution as well as being a quality item in its own right. I bought mine from JJC Race & Rally. Harness weight is 1.85Kg. I'm presently waiting on a Brey Krause bar from porscheshop uk to fit under the seat in order to properly mount the crotch straps.

Cooling system improvements

There is much discussion regarding the fact that the 996 as standard operates with a fairly high coolant temperature. The consensus seems to be that Porsche designed it to do so in order to minimise emissions but this approach is not ideal for longevity of the engine. As I track the car and will take it back to Australia I am keen to have it running as cool as possible so I have picked up a 3rd radiator kit and also a low temperature thermostat (Thermostat from Hartech). The 3rd radiator kit weighs 3.6 kg (plus additional coolant) - at least it's at the right end of the car and low!

Here are some tips in addition to the Renntech DIY instructions. My GT-3 front bumper was one of the types without a cut out for the 3rd radiator so I prised away the rubber part that surrounds the inlet and then used a dremel cutting disk to cut off the end of the protrusion that forms the air inlet for the 3rd radiator. It wasn't all that tricky and cleaned up tidily with a utility knife. In order to pull the wheel well liner out of the way you'll need to undo a 10mm plastic nut as well as the forward plastic rivets. To get room to work on the radiator hoses you'll need to undo the 13mm nut and 2x13mm bolts that hold the radiator bracket in place. Then move the radiator rearwards until the plastic protrusion at the front of the radiator slides out of its round rubber mounting bushing. The radiators can then be moved around adequately to work on. Using a flexible hose clamp plier makes undoing the OEM clamps a lot easier. The radiator can be mounted upside down as I have thoughtfully demonstrated in the attached picture - don't do it this way, the drain plug is far less effective. The rubber shroud should also be installed before the radiator is assembled into its brackets and bolted to the car.

Installation of the thermostat was reasonably straight forwards. A bucket full of water will drain when the thermostat housing is loosened. Accessing the bolts for the housing is easiest when the big rubber coolant hose is removed from the thermostat housing and also undo the three mounting clamps (10mm bolts) for the coolant line that runs near the thermostat housing. That hard line then can be pushed aside to access the thermostat housing bolts. I was able to dismount the thermostat from its housing without the Porsche special tool (I used a U shaped / wedged ball joint separator).


The charts below show some of the data I have collected with the new radiator installed.  The first 3 charts are a session at the track where the car was already pretty warm after having been driven on track 20-30 mins previously. Temps start at about 86c then climb to a max of 96c during the hard driving and then they have cooled to 88c after completing one 3mile cool down lap. By way of comparison, the car runs at 78c during normal road driving (Aug 2011, outside temps approx 20c)

Radiators: OEM vs aftermarket.

As this pic shows, it should be noted that there are differences between the aftermarket brands of radiators and the BEHR standard radiators. The aftermarket rad has a bit rougher finish to it but most significantly it has fewer coolant rows than the BEHR rad.


Cooling take II- Upper vented radiator & grilles.

Dec 2011. Since I had a bit of time off over Xmas I thought I would perform the modification to re-route the airflow from the 3rd Radiator. The modification involves tilting the radiator forwards,  blanking off the 4 holes on the underside of the bumper, cutting new vents in the upper surface of the bumper, fabricating some grilles for the vents, creating some duct work behind the radiator to redirect the air flow, cutting some recesses into the side radiator scoops and modifying the front rubber duct work for the 3rd radiator.

This is really quite a time consuming modification and I did it over several days and I installed grilles over the regular bumper inlets to prevents the ingress of leaves, rubbish and other matter that clogs up and corrodes the radiators.

I made a template for the vents based on some dimensions provided by Dervish at Reenlist in the 996 GT3 forum. I actually changed the dimensions slightly - primarily as a result of the method I used to draw/create the curvature. I have uploaded template diagrams I made whilst doing this mod. I used a dremel cutting wheel to cut the slots out, I used a dremel sanding drum to work the sharper curves and I used a dremel metal bit to round the tightest corners. These tools worked very well, the trick is simply to take plenty of time and be well braced whilst manipulating the tool. I used some sandpaper on a foam sanding block to finish the edges. See pic for tool details.

For the mesh I embossed it over another template cut from some wood about 4mm thick. I used a socket driver with some rounded and square edges to press the mesh into shape over the template. I then painted the mesh black and then used Tigerseal polyurethane sealer/adhesive to glue the mesh in place. As can be seen from one of the pics I used some toothpicks & string to keep the mesh snug in the vents whilst the adhesive cured.

** Update, Please note: after doing this mod a Rennlister pointed out that the OEM way of doing the tilted rad involves reversing the top section of radiator frame so that the tabs are towards the front of the car. I left the tabs towards the rear of the car and so the extension tubes result in a lot more forward tilt. This explains why I found it necessary to cut relief slots in the side rad scoops.

The duct for behind the radiator was fabricated from some thin aluminium and riveted together. It was a bit fussy assembling the radiator into the frame with the duct in place (because the hoses were hooked up) but it was do-able. The pic shoes that the ends of the duct are attached via two rivets. I drilled all the holes for the rivets but initially only attached each end by one rivet - thus allowing the end to rotate and make installation easier, then I assembled the radiator into the frame and fixed it to the car. There was then space to fit the second rivet on each end of the ductwork. The duct more or less prevents the air from flowing down or to the sides and the car bodywork is suitably shaped to direct the air upwards towards the vents. I bent the wings of the duct a little after the radiator was in its final position to close the side gaps more completely. I also put a felt pad between the wings and the body work to ensure there were no vibration noises from the duct/bodywork.

The rad was tilted forwards by using an aluminium tube of 8mm internal diameter and about 48mm long and using  m8x65mm stainless bolts in place of the original upper bolts. I also drilled an 8mm hole closer to the top of the upper mounting tabs of the  radiator upper frame and installed the m8x65 bolt through that hole as it is a better fit once the rad is tilted forwards.

For the front duct, using a dremel cutting disc I trimmed off about an inch along the upper edge shown by the green dots in one of the pics . I also made a 20mm slice in the area of the red dots in the same pic. This allows the duct work to flare out a bit as the bumper is installed. It's a bit tight for space when this all goes together but this didn't prove to be quite as big a hassle as I thought it might. In the end I tucked the trimmed upper edge of the duct into the space between the radiator and the frame. (much like the original). The lower edge of the duct was partially tucked into the gap between the frame and radiator. With the bumper in place the modified duct seems to be doing its intended job of directing the air to the face of the radiator.

On my 99 C2 I had to modify the airducts for the side radiators because the tilted centre radiator (and it's frame) protrude into the space occupied by the side radiator duct. The recesses I  cut into those ducts can be seen in one of the attached pics. I cut a triangle shape with the dremel cutting disc and then rounded out the shape using a dremel sanding drum. The drum was very quick and effective at forming the shape. I only used one disc and one sanding drum for the whole job.

Whilst I was at this job I made some aluminium mesh grilles to cover the lower bumper openings. These were also fixed in place with tigerseal and held nice & snug whilst the adhesive cured using the duct tape and string method that can be seen in the attached pics.


Track Camera GoPro HD-Hero Motorsports

I have replaced my trusty Hi-8 camera with a GoPro HD Hero 1080p Hi Definition camera. These are really amazing cameras, perfectly compact and suited to filming from within the car. The battery lasts a couple of hours and you can record a days worth of track sessions on a 32Gb SD card. It comes as standard in a waterproof casing which I promptly drilled a hole in so that I can leave a USB cord plugged into the camera whilst it is in the car (for charging or downloading the vids to my laptop).

The GoPro website is worth taking a look at for some pretty amazing vids.



Compact battery (Odyssey PC680) Aug 2011

In an effort to save weight compared to the large OEM battery I bought this battery and mounting system from the US. I wouldn't use this as a daily battery because it's capacity is not all that high and the 996 runs various electronics continually but the mounting arrangement lets me swap it for the standard battery on track days without having to drill any holes etc.

Note that a PC-680 is supplied without SAE terminals so they have to be bought separately. The mount weighs 1.27kg. The version I bought also includes provision for mounting a battery cut off switch. The battery itself weighs 6.8Kg.

Lightweight Lithium battery (Voltphreaks VPA-P6) Jan 2012

The VPA-P6 is an ultra light weight Lithium Iron battery weighing in at a meager 2.9Kg with terminals. The existing Rennline battery mount I purchased for the Odyssey battery works equally well for the VPA-P6. The VPA-P6 is a few mm thicker than the PC-680. This particular Lithium battery does not include a circuit to shut the battery down if it gets over discharged, hence there is a risk the battery could be ruined if say the alternator died and the car was kept running until the battery ran out of charge. I began by leaving the battery installed in the car on a daily basis and closely monitoring the voltage see how long the battery lasts under normal daily use - for me that means often having the doors open (& door lights on) for hours at a time while I work on the car. The battery proved to have enough capacity to deal with this type of usage.

After owning the battery for several months of UK winter weather I have found that a periodic (weekly) use of the battery tender has been sufficient to keep the battery in working condition. Typically I put it on and leave it on for 24-48 hrs or so. I have noticed that my battery charger only brings the voltage up to about 13.25v and that is more than adequate to start the car (albeit a little slower to start when the temps are around zero). I have measured the battery voltage after a decent drive, say 1/2 hour after stopping the car and the voltage is usually reading about 13.6v. The measured voltage seems to drop with temperature of the battery.

Issues - The most peculiar experience(s) I had with the battery was as follows. The weather was around freezing, I'd start the car in the garage and then go for a 2hr drive to the track, I'd stop near the track and fill up with fuel and then the car would not turn over. (for a while). Voltphreaks said the battery does better when it warms up from having an electrical load on it. So they advised me to run the fan on Hi or the headlamps on for 30 sec or so and then try to start the car. This 'workaround' did the job. Unlike a 'normal' battery this battery would begin turning the engine over very slowly and then increase in speed until the engine caught.

So to be fair, I never got stuck although there were those 2 or 3 occasions where I wondered if I was going to be stuck. With the benefit of experience I guess I know the battery can be coaxed into life using the 'workaround' under those freezing conditions.

I think a 911 is a challenging car for this battery because the battery does not get warmed by the engine and the battery is at the end of some pretty long cables.

Am I happy with it... Hell yes!

Lightweight Interior Aug 2011

Ok so at this point the with a roll bar and fixed seats in the car it has definitely been compromised as an everyday car with reduced flexibility coming from not being able to put much of anything behind the back seats. That being the case I took things a step further and made my own interior panels out of light weight materials in order to save some weight. Of course the cost of doing so is considerably increased cabin noise.

Update Dec 2011: I've now eliminated the side airbags and door speakers and am fabricating a cover to replace the centre console which will better suit the needs of mounting my datalogger and TPMS. As with the non airbag steering wheel, it was necessary to insert 2.7ohm resistors into the airbag plugs in order to simulate the presence of the airbag and prevent an airbag failure light.



Carbon fibre sunroof Feb 2012

This became a bit of a spur of the moment modification when I was offered a CF sunroof panel and Alcantra roof liner at a good price. I subsequently removed the OEM sunroof (weight 12kg) and installed the CF panel with Tigerseal adhesive. The end finish turned out very good (other than I had to use grey tigerseal due to ordering the wrong colour and then running out of time to fix that issue.) The trick with this install was to use some aluminium strips to bear the load of the CF panel. Tape was applied to fix the panel in place in the fore/aft & Left/right axis. and also to close the gap so that there was a floor for the adhesive. I then placed half a dozen various weights on the panel from above to ensure that it was flush with the roof line. That worked really well. I let the adhesive cure for 48 hrs before moving the car. It has since done several track days and no issues. Also no leaks when I have washed the car.

Surprisingly I was able to remove the sunroof without removing the seats & roll bar.

Following on from this activity I have installed an alcantra non-sunroof roof lining (996.555.091.04). It was supplied to me without metal rods so I had to buy some 5mm stainless steel rod and make up new rods. Note each rod length is slightly different and also fairly critical as the rods need to fit to length snugly so that they do not rattle and do not bow excessively. The rods fit into plastic receivers (Part no 5 in the diagram) that are already in place even though not all of those plastic receivers would have been used in a sunroof car.

I also discovered that the non sunroof roof liner uses a smaller surround around (Part no 8) the interior light.  The smaller surround is part number 996.555.557.10 which cost about £37 from design911.


Hood catch 9 Jan 2011 Back to top of page

When I bought this 996 two minor things were known to be not working properly, one was reversing lights not working and the other was that the hood didn't pop up after being released. I set about fixing the hood catch today. This was a fairly straight forward task. First remove the plastic trim piece which covers the catch by twisting the 4 plastic tabs 90 degrees. Then I removed the front section of carpet from the luggage space by removing the 5 plastic clips that secure it. Unclip the alarm wiring from its plug and then rotate the plug about 40 degrees to release it from its bracket (see pic A). Undo the 2 x 10mm bolts which secure the bracket. Set aside the stainless steel backing plate for the catch. Pop out the emergency release cable from the catch. Push through the rubber grommet and then the plastic plug for the alarm wires (it will fit through the hole). Then pop out the hood release cable and its rubber boot and then the catch can be removed from the car. Next pop off the alarm switch cover which is held in place by two plastic tabs (See pic B red arrows).

In my case the spring was still seated in the hood locking lever but it had bent beyond 90 degrees and lost some of its spring force. I used a beefy needle nose pliers to bend it back to 90 degrees as per the green line on pic C. Bending the end of the spring may be a little easier if you pop the other end of the spring over it's tang (yellow arrow pic D).

I tested the operation of the catch before and after bending the spring by rotating the locking catch to its locked position (Pic E), use the shaft of a small screw driver to press the lever into the locked position. Pic F shows the catch NOT working ie it has been released but it has not rotated into its correct position (Pic D shows the catch in its correct position after being unlocked - It is the tail end of this catch which pops the hood up. After I bent the spring to 90 degrees as described and made sure the spring was snugly seated in the corresponding hole in the locking catch I found that the locking catch would snap up to the correct position with a positive sounding click.

Oh there was one other bonus - my luggage area light started working - it was obviously operated by the switch which is in turn operated by the locking catch!

 A B C



Light Weight Hood & Vinyl Graphics: Jul 2012

I just happened to be surfing ebay a couple of days ago and discovered this ex race car GRP hood going for a price which was too good to pass up. I had previously considered a CF hood but at £700+ I wasn't that keen. This hood weighs 5.5kg vs 14.4kg for the OEM steel hood... so now it's mine. The hood is in quite good shape, mainly just one big scratch and some chipping of the pointy corners. So I have set to work with some filler and I have the car booked in to Spectral Designs SW of London to wrap it in CF since I'm not inclined to paint a hood which is going to see track duty. Even though my sunroof is already genuine CF I'm going to have them wrap the sunroof as well so that the sunroof and hood match. This is also the catalyst to add a purely cosmetic touch to the car by having Spectral designs  do a vinyl graphic on the side of the car. At this point in time I've also decided to add a personal label to the car, hence the RS 3.4. So far as I know there never was a 996 Carrera RS 3.4 so I don't think I'm guilty of imitating something else. I like to think that the RS 3.4 label is indicative of the lightweight Renn Sport ethos to which I have built the car. This RS 3.4 label might also help reduce the  instances of people thinking the car is a GT3 with a Carrera badge which has happened several times lately when I've been at the track.

The hood uses M6x45 bolts to attach to the OEM hinges. One thing the hood doesn't have is an attachment point for an OEM latch so at this point it is purely secured by the hood pins I have installed. Those pins are very simple to install by drilling through the sheet metal that the normal rubber hood height adjuster rests against. I will need to fashion a new means to ensure that the hood sits at a correct height behind the bumper and to me I'd like it to sit a fraction lower than the bumper in order not to sit proud into the airflow coming over the bumper.

Other points to consider are that with no latch the alarm will always think the hood is open unless the latch switch is electrically bypassed. The trunk is also less secure without a latch. Finally I doubt the sealing is as good with a lightweight hood so the contents of the trunk may be more prone to water/dust ingress - time will tell on that one.


Aerocatch hood pins

Initially I installed a basic hood pins because the hood already had been drilled for them and it allowed me to get mobile with the new hood.

However for the longer term I needed a solution that would allow me to lock the hood as failing to do so would leave the car insecure since it doesn't have a regular hood latch. Aerocatch hood pins were the logical answer. I was a bit unsure whether there was space to fit them but obviously form the pics the answer is yes they do fit. There is not much room for error when doing this job so it was definitely a measure twice and cut once operation. I spent the best part of an afternoon doing this job. Part of the time was taken making the custom load spreaders which is the aluminium oval that can be seen in one of the pics. I made those because I didn't really like the fact that the aerocatch mounting screws are very very close to the edge of the hole that the catch sits in and the kit only includes tiny washers to bear the load of the mounting screws. The load spreader does a much better job




OEM VS Original Parts.

Here's my take on this subject. Sometimes the aftermarket parts are the same as the originals, sometimes they are not.

When it comes to coffin arms, the TRW parts are Porsche parts with the Porsche symbol ground off.

When it comes to other parts there are visible construction differences ie aftermarket MAFs and radiators. Cheaper probably does mean inferior quality or performance in my view.

Other things like Brake disks (Pagid/Zimmerman) may appear slightly different in construction (rear disk drilled pattern) but seem to work equally well in my experience and are thus worth saving money on. Likewise with O2 sensors.

So when it comes to fitting a part that involves a fair bit of labour or is a critical system pay for quality rather than risking a critical failure or repeat job.


Radiators: OEM vs aftermarket.

As this pic shows, it should be noted that there are differences between the aftermarket brands of radiators and the BEHR standard radiators. The aftermarket rad has a bit rougher finish to it but most significantly it has fewer coolant rows than the BEHR rad.




Reversing Lights 14 Jan 2011 Back to top of page

The reverse lights in my car didn't work when I bought the car. I checked the reverse switch when I had the trans out of the car and it seemed OK. I checked the globes and they were OK and then I found that the fuse was blown (Fuse B5). However after replacing the fuse the problem persisted. I went back to the switch and verified that power was reaching the switch and it was. I then took the switch out and checked it again and it was working. I scratched my head and engaged reverse and the lights came on. Grrr. I figured my messing around with the switch had disturbed something enough to make it work again. The happiness was short lived though as I found that sometimes the reverse lights came on and sometimes they didn't. Since the switch only costs about £15 I ordered a new one and installed it when I did my gear oil change on 14 Jan 2011.


Bedford Autodrome trackday 22 Jan 2011 - The fun begins.

It was a cold, damp and drizzly day that saw a good portion of the attendees in the runoff zones at some point but it was a great location to do the first track day in Emmy. Had a great time working up the car and managed to stay out of the weeds. Unfortunately I did manage to exceed the drive by noise limit in the afternoon as I picked up the pace and earned myself a place in the sin bin/spectator ranks - but not before getting a decent feel for the car. All in all a very enjoyable day and great crowd. Bedford runs a 101dB static noise limit. 87.5dB @ 20m drive-by limit.

<-- Mates Daz & Ric getting the R-32  ready (Ric being the good bloke that he is,  let me get some seat time in his Skyline after the 996 was banned for exceeding the noise limit - gotta love boost)


Porsche Experience Centre

April 2011

I had booked myself in for a you-drive session at the Porsche experience centre, primarily to have a crack at the kick plate which kicks the back end of the car left or right as you drive over it so that you get to experience and correct an oversteer situation. Your on an ice like surface after the kick plate has done it's thing so this is quite a unique setup and worth while doing. During my visit there the Ice hill was unavailable due to maintenance so we had to suffer with driving a new PDK Cayman R around the low friction (snow like) surface. That was definitely good stuff. The experience also includes driving a new 911 around the handling circuit (roughly 1km long and relatively narrow), for that I was handed the keys for a 385Hp 997 Carrera S PDK so that was handy as something to compare with my 996 and I gave that a decent push around the track.  As it happened I managed to top the human performance challenge and was rewarded with some pax laps in a new 997 GT3 with Ex rally champ and Porsche instructor driver Jeremy Palmer doing the piloting. We spent that time between the low friction circuit and the handling circuit putting in fast laps and demonstrating car limits. As I peered into the wing mirror frequently looking at the clouds of tyre smoke billowing from the GT3 as we travelled sideways around the low friction circuit, I figured no one could see what we were doing as I'm sure the entire circuit must have been shrouded in tyre smoke. Jolly good stuff really!

I think my experience may have been a bit better than average but I sure as heck had a great day. I'm also booked in for some one on one driver training with a Porsche instructor driver next week.


North Weald - take II

I headed back to North Weald for a day with Andy Walsh (Lotus Elise series driver) after my previous day was a bit of a non event due to the car understeering so badly. In the mean time I had installed a GT3 sway bar and widened the front track to reduce understeer so you can imagine I wasn't really happy to discover the car was still understeering on the 285/225 combo - this really highlighted to me just how critical tyres are with respect to handling characteristics. In particular it reinforces the point that even with a tried and true tyre/suspension setup - the handling can still go astray due to tyre condition ie  age (hardness), mileage, tread depth.

Andy being the good bloke that he is offered his spare boxster wheels (255s) to go on the back in place of my 285s so we bolted them on and bingo we got some (actually lots) of oversteer to play with. Since that's what the day is all about I finally got some value out of it - ie practising dealing with oversteer correction.




Porsche 996 North Weald circuit video with Car Limits Andy Walsh.

(44Mb .mp4, right click & Save as)

Snetterton April 2011.

27 April turned out to be a nice sunny day to head to the track at Snetterton. I had hoped to get to the track with my Toyo R-888s but that didn't happen as I have decided to buy some new track wheels which I couldn't get in time for the event. So I took my road wheels and the rather old and hard (7yo) tyres that still happen to be fitted. There was a track photographer present and he got some helpful shots of the car under corner loads which is quite helpful for me considering I'm trying to decide on which wheel offsets I should go with for the new wheels in order to maximise track without having tyre rubbing issues. The pic to the left was handy in showing the rear tyre tucking into the fender nicely under load. Based on these findings I'm aiming at 18x8.5 ET 40 Fronts and 18x10 ET 65 Rears to suit my 235/285 Toyo R-888 track tyres. Standard front offset for mine is 50mm and I have been using a 15mm spacer with my 225s to achieve an effective offset of 35mm but the 235 Toyo will fill the arches a little more - hence the decision to look for an ET40 front wheel to give me an additional 5mm clearance for the 235 R-888.


Snetterton 300 August 2011

This was the first day at the track with the roll bar and seats fitted to the car and also my first time at Snetterton with track tyres fitted. I haven't made any further changes to the cars suspension setup as it seems to be handling pretty well both from my own perspective and a couple of instructors who have been in the car with me recently. This particular event included a real bonus in so far as I was able to take instruction with Tim Harvey, Porsche Carrera Cup GB champion in 2008 & 2010. Clearly it's hard to beat getting instruction from the champion in such a class. What was really insightful was having Tim Harvey drive my car around Snetterton to demonstrate a number of things and in effect show me what my car could do when driven skillfully. It was a brilliant opportunity. It was certainly an eye opener for me and has given me plenty of things to think about and work on for the future - Thanks Tim..

The final bonus with this day was that I was running with a  Race Technologies DL1 Mk3 Data Logger. I ran it with just a power connection and the GPS antenna stuck on the roof. This has proved invaluable for being able to review and compare how I tackled each segment of the track. A Big thanks to 911UK MisterCorn for making that possible!


Sep 2011: To the right is one of the laps I drove whilst I had the  data logger in the car. As of Sep 2011 I used the software that comes with the data logger to overlay the gauges and timing information onto the video. To be honest at first I didn't think the overlay video was all that important compared to analysing the data - until I compared it to the video (with overlays) with Tim Harvey driving, I stand corrected ie the video with overlays conveys additional information that may not be so clear from looking at the graphs in the analysis software.


The YouTube video above shows Tim Harvey talking about the 2011 Porsche Carrera Cup GB series.


Donington GP Circuit 9 Oct 2011

The weather forecast deteriorated as this day drew closer so the evening before with no improvement looking likely I elected to take the track wheels (R-888 tyres) off and fit the road tyres (PS2) instead.  At 5AM when I got up to it looked pretty bad with pouring rain so I wasn't expecting this to be a very good day. It rained for most of the 90 minute drive but petered out a few miles before I arrived at the track. When I got there it was cool and the ground was wet but there was no standing water at least. Oh well.... I thought it wont do any harm to practise in some slippery conditions. Greasy is pretty much how it started, but it didn't rain any more despite being cool and overcast and looking like it might do so. So as the day progressed the track began to dry out on the common line and grip continued to improve. By the end of the day most all of the track had dried out.

At this event I had a coaching session arranged Tim Harvey. Having previously received some coaching from Tim at Snetterton and some further guidance at Oulton Park I had learned a lot (OK maybe it doesn't show) and I had been practising those skills, this subsequent session proved valuable to get some more feedback and the high speed flowing curves of Donington provided opportunities to highlight additional techniques for car handling. Since this day started off damp it was also a bit of a contrast in terms of lessons received with Tim during dry conditions. This was all excellent stuff and whilst some lessons only get learnt when your ready to do so, I'm sure that the lessons I have learned from Tim Harvey have had the greatest impact on my driving thus far.

I have also invested in my own Race Technologies DL1 Mk3 data logger at this time and between the instruction from Tim, the data from the logger and the video from my HD Hero Camera, I can see plenty of areas where I need to improve what I am doing, work on some finesse and aim for consistency.

So in the end this day proved to be excellent. It would have been nice to have had the track tyres on the car in order to exploit the extra grip they offer but in reality they would have been marginal early in the day and it probably didn't hurt to do the day on road tyres on a wet track at a time when I am going faster than before.

Gallery from the day

Above: A full HD Video session on the Donington Park GP circuit in the 996.




Donington GP Circuit 15 Oct 2011

Myself & regular track mate Ric Hands arrived not long after sunrise and were quickly unpacked and we had the cars prepped and sorted for the day with a flask of coffee getting the day started. Despite being mid October this unfolded as beautiful warm day, completely dry and blue skies... what more could a track junkie ask for (apart from more power, better suspension, lighter weight... ah! I digress). A few forum members attended this particular event and so were rewarded with some excellent driving conditions.

It turned out to be quite a social day with lots of people interested in saying hello and being interested in pax rides. There were also a few minor dramas to make the day interesting. Ric's Skyline decided to split an intake pipe after the first session and so he couldn't make any boost and his car being MAF based didn't like that.  I'm not sure if John had done anything similar with his GT2 but he was quick to a creative rescue involving a tin can, some duct tape and some nylon ties and the skyline was put back in motion for the rest of the day in that shape .. still running about 1 bar of boost (400hp) too!


After meeting our 'neighbour' I went for a pax ride in his Tiger which was just superb on a day where the conditions were so nice. Andy has since posted a you tube video from the day which can be seen to the right.

I also went for a spin with Peter in his 996 C2 Cab. I must admit it was nice to get around with the top down and hear the howl of the Porsche sports exhaust.  

Since the conditions were much better than the week before I was able to run my track tyres and take another few seconds or so off my previous lap times thus getting my time for Donny down to 1:56.7Sec on the GP circuit.

Click picture for full size view.


Above are some HD laps from an afternoon session.

This is Andy's Tiger in which I enjoyed a few pax laps on the day, the video shows what a great day it was to be getting around in an open top car.

May 2012 Coaching with Mike Wilds.

I had heard of Mike Wilds through the grapevine and noted that he had a very good reputation as a driving instructor. I met Mike at Donington one day and found him to be very personable and I subsequently booked him for a full day of instruction at Oulton Park shared with a mate (Ric / Skyline R-32 GTR). Since we were all staying at a hotel to be convenient to Oulton, we met Mike the evening prior to the track day and talked through the plan for the following day over a meal.

Ric and I both had a good amount of track driving experience at this point but we both also gained considerable benefit from Mike's coaching and we both found his coaching style to be excellent, informative and non-pushy. Mike has a considerable amount of professional racing experience both in terms of car types, racing circuits and racing conditions and I felt I was really benefiting from the insights he provided and the observations he made regarding areas that I needed to improve upon.

I have no hesitation in recommending Mike's services to anyone that wishes to improve their track skills.

Mike Wilds contact details and information are on his web page here.

23 Jan 2011 OEM Adjustable GT-3 Wing  &  Track Wheels Back to top of page

Yesterday was a great day at the track and today also happened to be a particularly good day as well. I managed to pick up an OEM GT-3 Mk-1 Aero Wing in a favourable exchange to replace the cabriolet wing that was on the car when I bought it. As of 25 Jan the wing is in at the body shop being prepped for a coat of arctic silver.


20 Feb 2011: Wing & spats installation. 

I got the wing and spats back from the painters who have done a great job. I gave now installed the wing and also the spats onto the rear bumper. The spats is the trickier of the two jobs since I didn't have a template. I made one up but wasn't entirely happy with that as some of the holes had to be elongated to correctly allow the bolts to pass through. What worked best for me was to use a piece of blue tack to transfer the hole position from the spat to the bumper. I used a piece of blue-tack about the size of a quarter and about 2mm thick, I applied a bit of olive oil to it to reduce its tackiness on one side and then I placed that over one of the threaded holes in the spat. I then put the spat in place and pressed it firmly against the bumper. The blue tack remained stuck to the painted side of the bumper and there was a raised portion showing me where the hole would sit. I then stuck a sharp pointed object through the centre of the raised bit of blue tack to mark the centre of the hole on the bumper. Then peel the blue tack away and drill the hole.

I'm glad I went to the trouble to get and install the spats as I always felt the rear bumper looked like it was  missing something without them.





Useful Links for 996 owners

Detailing page

Porsche Workshop Manuals & Porsche parts catalogue (PET) application

Option codes    OBD II Error codes  Wheel offsets  HVAC Diagnostics Trick  My 996 Newbie Good guts guide

Porsche Technical Service Bulletins (paid access at Renntech) Renntech - Look up prices on Porsche part numbers

Porsche 996 Essential companion - 656 pages of good info.

You Tube also has a variety of 996 videos, DIY guides etc

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Below are the vendors that I have used & found to have good gear or service when shopping for Porsche parts.

* Don't believe everything you read on the internet *



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What's not to love about the track ?

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