[Skypalace]

Coolsuit weight depends on size. Large is about 30 lb with ice, I run the small FAST setup that's about half that, the ice will last about an hour on a very hot day, 90-120 minutes on cooler days. I run it any time the ambient temp is above 70, and often below that for practice & warmup.

For me it's not about staying cool per se (once I'm on track I don't notice temperature or other physical discomfort etc., I'm too focused on driving), it's about not getting so hot that my mental or physical performance is compromised. Pre-cool suit I was starting to making mental errors and having to back off the pace towards the end of races on hot days. Of course it's the day I got heatstroke (running 5 race groups on a 104 degree day) that broke the camel's back :-)

I'll gladly add the 15 lb. for increased mental performance, even minimal, in the last half of a race. Given that I'm ~2800lb with driver, that's .05% extra weight, or about two gallons of gas, or about 2.25 horsepower given power/weight.

If you're that worried about performance, the engine drag from the AC compressor will hurt you more than the weight of the AC. I'm not sure if the Porsche disengages the AC compressor when at 100% throttle, if it does then you should be fine, as it just means you're burning a little more gas (ie. at say 45% throttle rather than 40% throttle in a part-throttle sweeper) rather than reducing full-on performance.