Here's how I'm testing the cars. All four, driven by my class 31 b-spec pro, M. Cooper. (No joke.) Here, I will post his times for us to draw conclusions. All races are done built to spec, no tune, and on racing medium tires. I also keep his attitude neutral race long, and there is no tire or fuel wear. The race of choice is 10 laps on Trial Mountain.
Acura NSX RM
best lap - 1:35.881
total time - 16:14.222
Honda Integra RM*
best lap - 1:38.372
total time - 16:50.844
Mitsubishi Lancer RM*
best lap - 1:38.583
total time - 16:44.234
Subaru Impreza RM
best lap - 1:36.405
total time - 16:23.080
After some thinking that the Honda Civic would perform better than the Integra, I had M. Cooper give it a go. I also tried the Lotus Elise for good measure.
Honda Civic RM*
best lap - 1:39.675
total time - 17:05.689
Lotus Elise RM
best lap - 1:31.871
total time - 15:34.439
*Do to consistant traffic, the Integra, Lancer, and Civic all ran slightly slower lap times. With each one, it seemed to be about a 2 sec difference a lap, or 20 sec overall.
Conclusion: I see two options.
1. Allow 3 cars: Impreza, Lancer, and NSX. Restrict all cars to 415 hp. The nimble characteristics of the lighter NSX compensates for the extra grip of the AWD cars.
2. Allow 5 cars: Civic, Impreza, Integra, Lancer, and NSX. Restrict all cars to 350 hp. Each car has it's own advantage. The NSX handles best and has the highest top speed. The Impreza and Lancer benifit in low grip scenarios. And, the Civic and Integra have the lightest weight and most predictable driving characteristics, but suffer from excessive tire wear.