Quote:
Originally Posted by mikeyjd
This is similar to what I was looking for. The one I was thinking of was posted by Darin I think, and it displayed mph on a grid with aero % increasing incrementally. Something like 20mph = 30% and 40mph = 50% . It was a nice looking graph and I just wanted to have it on hand for reference.
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*The drag FORCE varies as the square of the velocity:If you double your velocity,you're hitting twice as much air,twice as hard.
The Power required to overcome the drag force varies as the cube of the velocity:When you double your velocity,you're hitting twice as much air,twice as hard,twice as often.
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When you know the 'starting point' for your car you can throw in a new drag coefficient,holding everything else constant and see how it impacts the road load horsepower for any given velocity.
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Top speed is achieved when power-train losses,rolling resistance,and aero drag equal the brake horsepower of the engine at whatever conditions you're operating at.
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The mechanical efficiency of the power-train is essentially constant at full power so you can just discount the brake horsepower by that fractional multiplier,then any drag reduction allows a speed increase which balances the new aero load and new(higher) R-R value at the higher velocity at that discounted horsepower.