krisa9977

I spent a lots of time with Porsche GT3 991 at the race track before I found proper setup(wheel alignment) for best possible lap time. The difference from the car with standard setup from the factory and optimized setup is huge! With my setup(only wheel alignment and ride height), I had 3.5 second lap time improvement at 3 miles race track over original factory setup. It it possible to make the car even faster, but front camber is limited with the bolt length. The bolts of the front control arm are to short and it is not possible to put more shims to increase negative camber.

PierreTT

Please share this setup!

krisa9977

Lowest possible ride height in front with maximum possible negative camber(need to use shims). 2 mm in total toe, softest roll bar

Rear is a bit tricky. Camber anywhere between -3.1 to -3.6, 6 mm in total toe, softest roll bar. You need to adjust your rear alignment according to the track and your driving preferences.

Manifold

What front camber did you wind up with?

krisa9977

about 3.1. I did not try to rotate top mounts yet

Manifold

Thanks.

I tried increasing cambers to -2.0 and leaving everything else factory, and the car seemed decent. A pro who knows the car very well advised me to go back to factory -1.5 cambers, and the car felt better, maybe a little faster too, but I didn't have good data to compare. I recently ran across a guy driving a 991 GT3 (very fast) who changed his setup similar to what you describe, and said it significantly improved turn-in and cornering grip.

The whole setup question is confusing to me ...

krisa9977

My student qualified first and finished second in Porsche Sport Challange race with those settings. It was warm up race just before DTM. 20 identical stock 991GT3s with factory roll cage on Cup2 tires. Absolutely no modification allowed. The only thing that we could do was to play with the alignment.

https://video-mia1-1.xx.fbcdn.net/hv...a7&oe=55F0D9B7

Mike in CA

Although I was able to get -2.2 in front without shimming, and I'm happy with the result, just FMI I'd be interested in hearing more about this. I was told that, unlike the 997 cars, rotating the top mounts wasn't possible/had no effect (can't remember which for sure). Was I given bad info?

krisa9977

I'm not sure about rotating top mounts on 991GT3. There is no clubsport position like it was on 997 GT3. I did not try to play with top mounts yet. The best way to increase negative camber is to add more shims, because this way you increase front track as well. Wider track is always better for grip.

BTW. I tried factory -1.5 setup and -2.1 setup. For some reason factory setup works better. But when you go "extreme" with camber, its getting much better again. The problem is rear end stability. With aggressive setup you gain a lots of grip, but your rear end becomes unstable. You have to be very smooth, transferring the weight to rear wheels at mid corner. If you increase rear camber to -3.6 degrees, you'll get very stable car, but you also get a lots of understeer. But if you'll adjust your driving line and driving style, it is possible to go much faster.

Mike in CA

Thanks. I'm running -2.2 front and -2.5 rear, middle setting on the bars, all other settings within factory limits. This setup is definitely quicker than the stock -1.5 F/R for autox and it feels better to me. Overall grip is improved, as is turn-in in tight corners and slaloms without the rear getting twitchy. I've noticed no ill handling effects on the street although it's too early to tell about tire wear. With regard to your experience, maybe it's the difference between a track setup and one for autox. I haven't tracked my car so I can't say how well these settings would work there.

krisa9977

autox settings are completely different. Slower the corner - more understeer you got. All the cars, in general, have a tendency to understear in slow corners and overstear at fast corners.

krisa9977

This is setup for autox )))) You don't need GT3 for that )

Mike in CA

haha.....back in the early '70's when I started autocrossing with a Lotus Europa, Minis were more common. You don't see them very often today, at least not the "real" ones. I enjoy the GT3 for autox; I know I don't need it for that but it's a competitive autox car that I don't have to prep and can also enjoy on the street.

Manifold

Ah, interesting, that may explain it, maybe I've only tried the first half of a U-shaped curve. Any thoughts on why there would be such a curve?

krisa9977

I have no idea why. I also know that you have to be very fast and very smooth driver and drive your car 100%, especially at mid corner to take advantage from aggressive race setup. I saw that "average" driver can go faster with factory setup. When we put less experienced driver in a car with more negative camber, he didn't like the car and his lap time was slower. When the pro driver jumps into the car with "race setup" his lap time 3 second faster over the same car with "factory setup". If you don't use all available grip at mid corner, you don't need more negative camber