This is incremental but I would say 200 hp for every 1000lbs is a minimum point for non momentum cars. Keep in mind we are not talking keeping momentum such as Hamilton versus Roberg et al.
Additionally you have some very fast cars that I would call semi momentum such as a USAC midget or Formula Atlantic.
Non momentum cars are pretty easy to identify; Cup cars, F1, Indy Car, Sprint cars are obvious ones.
For the sake of what we here drive momentum cars are going to be Miata, FRS, Datsun 510, NA MR2, Boxter. Starting around Caymen S, WRX and S2000's you are getting into the incremental zone.
Weight is a factor as well so for road cars I'd say over 3200lbs and 400hp would be non momentum.
For the record I run a 1500lb car with 80hp at the wheels, I have also run a Dsports racer that was 1000lbs with 175hp capable of out accelerating your basic Viper and turning very fast lap times but it still was a momentum car. 175hp just isn't enough raw power to push through the wind at 130mph like there is with a 700hp car. Having a car on the ragged edge cornering means there is not a lot of traction left to accelerate but if the car doesn't have any real acceleration it doesn't matter. If you have 600hp giving up that 10th of a mph may allow you to unwind the wheel earlier, flatten out the car and be on the gas earlier playing to the cars strength.
IF your driving focus is on entry and corner speed then you are in a momentum car, if your focus is getting good bite off the corner then you are not.
Tom
