I found this in my old emails (from 2007) whilst searching for something else. I don't remember who the guy who sent it me is but he had some good friends at Porsche who were involved in the CGT development and he answers some of my questions below including lots on my query about why my, and other CGT tests, could only do 0-300kph in ~32s when the factory got 25.Xs....... It was nice to re read this, quite interesting :)
First of all, the figures published by Porsche were obtained from the Weissach cars. The cars used standard pump fuel up to 100 RON during the testing period. These cars were not fitted with any “special” enhancements. Jens drove the vehicles throughout the test program as did others and confirms that no “special driving techniques” were employed by anyone for the purpose of the published figures. “The figures are always signed off at top level before being released and that needs a lot of evidence to gain signatures.”
He is positive the figures published were achieved and says sometimes were exceeded. “The Porsche philosophy on publishing performance figures is that ALL production cars must be able to confirm the figures quoted. This often means lowering the “best” figures obtained during any testing for the poorest denominator as cars do vary a little.” I guess that is where the traditional Porsche understating comes from? So were Porsche on a marketing trip with their claims? I have to say, based on my discussions with two good friends, no. Well not intentionally anyway!
Generally the guys were perplexed at your figures and could only point to the obvious considerations. Jens did say that he had also seen worse times than yours during development but these were for a reason
and mainly consisted of one or even more of the following being out of spec…..(so many I had to keep writing them down!) Sorry if it seems I am teaching you to suck eggs! Hey, they did it to me and I was also yawning, so here it is!
Tyre condition
Tyre temps and pressures
Weather
Wheel alignment
Engine service condition
Weight
Road surface
Mechanical service condition
Damper performance
Clutch performance
Rear wing position and performance
Fuel quality
Driver error
etc; etc; etc
The basic message was that everything should be “in spec” for the car to perform well. (obvious) Thomas is adamant that the asphalt surface will play a larger part than most people think. “We have known this for many years from extensive testing on different surfaces at Weissach and the Nordschleife.” He would be surprised if your car was the reason. I would agree only because the time gap is so large. I drove a 2004, 105,000 km car at the weekend, this really felt no different than mine! Unlike 911/993/996 where you can certainly tell the difference in high mileage even with a blindfold, this CGT was the same as mine. This can only point to the design and build quality. Superb.
Interestingly, did you try the run in the opposite direction? They both agreed that the lower performance was more than likely due to increased drag on the car or full power/traction not being achieved. Gear changes were good and not an issue. However, as you can appreciate, it was not possible to pin point any certain reason.
Finally, they suggest you try the run again, preferably on a different track and monitor the results. If they are the same, Thomas’ suggestion is to have the car checked over and maybe Dyno’d if nothing is found.
At the end of it all, Thomas said in his heavy German accent “You know, all this is not important, what is important is one lap at the Nordshleife!” I love that statement so much I have to use it on my signature!
Like you I find it amusing how the rumors and theories develop -like the clutch ECU software mod !Some guy posted recently as if it is fact that '05 cars have this mod which makes the ECU increase the load for a hill start..... In fact the recent Porsche Post (PCGB), the one with the Red CGT on the front, the author inside also refers to the later cars having easier to get off the line clutches.....
One issue which I am interested in is the ride height. Some people say the US ones were higher than Euro ones. My ( US ) handbook states 86mm and that is exactly right for the front splitter - I really can't see how Euro ones can be lower ? Confirmation would be great...
Thomas could not think of any differences between US and ROW Motronic programs, except for the fuel vacuum pump program on the US version. He maintains that there should not be any differences between a US car and an EU car in terms of designed performance. It is possible to download the ROW program to your Motronic if you so wish.
With regard to the alleged “hill start program”, Thomas has never heard of it! Having read some of the other posts, I would suspect that what the yanks are referring to is ignition advance. This will occur whenever the engine senses a high load and it will be blatantly apparent at low revolutions when it acts like an anti-stalling measure. This will give the impression of a “blip” from the throttle at just the right moment, but of course its not. The increase in revs would only be noticed when the load has been overcome or the load has ceased to be. Ie. quickly disengaging the clutch. So their description of exactly what and when it occurs is not entirely accurate which is why you probably could not reproduce it.
Car height: Again, there is NO difference in car heights between US and ROW. There is a slight adjustment that can be made on the lower spring retainer that was provided for a simple reason. As vehicles become older, they will get lower, spring tension, bushing etc. and this may cause damage to the underside.
The rollbar is set to the middle position during production as the standard spec.
I asked a whole heap of other questions which Thomas has promised to get back to me on as well as elaborating on your specific questions. He needs to call around a few departments to get the accurate info. Should have the answers in a few days.
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997 GT2 2014 3.9 Mezger, 800PS @ 1.2 bar
2018 McLaren 720S
993 Turbo, 2006 built 3.8, 577PS/797NM, 1440kg DIN sold to a worthy enthusiast.
). 
- very interesting. I have to get a Carrera GT at some point but must be a flat black - they look so wonderful.
