Both T/F and F/C spin the tires all the way down the track, they have to. It's obvious when they do not have enough wheel speel, it's called tire shake. If you have too much wheel speed you are going to smoke the tires. The power limited acceleration as modeled above is not accurate as the cars in both fuel classes have more than enough power to spin the tires regardless of the down force provided by the wing. It is controlled by the tuneup by programming the timing, fuel flow, clutch setup and other settings that can each be set to change numerous times during the run. It's all a matter of programming the car systems to make the maximum amount of horsepower needed to get the car down the track with the maximum tire spin but not smoking the tires. It's rare if they are producing the maximum horsepower the engine can produce all the way down the track. Listen to numerous tuners at the racers and there are times they have a very difficult time backing the car down enough to get down the track. Never have heard a tuner say they didn't have enough power, it's the tuneup settings that determine how the power is used and how much is needed and when. It's the clutch slipping- how much and when, timing change and fuel changes all the way down the track. In Denver which is the high altitude track the fuel cars are allowed more blower overdrive, wing angle and a higher nitro percent as there is less air resulting in less horsepower thereby screwing up their normal tuneup. With the above changes they can run much of the same tuneup as they do at sea level.