springer3

Aerodynamics is complicated. This is simplified, but basically correct. The more powerful car will start to pull away noticeably at about 45 MPH. Above that, there will be no contest.

Wind drag force increases with velocity squared (V^2). Power to overcome the drag forces increases with velocity cubed (V^3). The slope of the wind power curve is getting pretty steep at about 45 MPH (about the speed where the spoiler deploys).

These numbers are a guess, but are reasonable. At 50 MPH, wind drag requires 5 HP to overcome. By 100 MPH, overcoming wind resistance is costing 125 HP (5^3).

If you accept these numbers, a 4000 lb/400 HP car is accelerating 1.2% faster than a 2000 lb/200 HP car when both are at 50 MPH. At 100 MPH, the 4000 lb/400 HP car is accelerating almost twice as quickly.

Remember all other things are equal, so both cars have 1000 HP brakes, and the 2000 lb car will pull twice as many Gs in the turns. Things will be a lot more exciting for the 4000 lb car at the end of the straightaway, but it will have a substantial lead.

tonytaylor

To say F=ma is of course true but hp isn't a force but work done and while the car certainly has mass, "m" it also has weight. For the acceleration in F=ma a 400hp4000kg carand a 200hp/2000kg would be the same and this is "inertia". However there are other forces that need to be overcome of aero resistance is one but forces relating to weight are also relevant, that is, friction - try pushing a 4000kg car at a constant 2mph and a 2000kg car at the same speed and see which is easiest. 2mph is a constant speed so there is no acceleration and aero resistance at this speed is negligible but the heavier car is still harder to push.
Aero resistance is dependant on both the Cd or "shape" of the object and it's size. My motorbike is very unaerodynamic compared to a car but can do 125mph with only 60hp and since it does have some mass not all this power is used overcoming drag. At 45mph a 400hp4000kg car would still be losing ground on it
I would say power/weight upto 100mph and power/drag over 120mph.

Flagg

We just need to prove it. Someone needs to strip all they can out of the car, down to say 2,500 lbs and have a stock 247 hp engine. Then we need someone to have a turbo engine in a 964 making 500 HP - and then load the car with 5000lbs of lead weight

My gut feeling is that the 5,000 car would win a in straight mile drag strip. The 2,500 pound car would win on a track, due to braking and corning........

Flagg

AJKOK1

Sounds like a plan. Anyone want to "lend" me a 964 Turbo Engine, I'll test it out and promise to send it back in one piece ( honest).