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      06-04-2013, 02:01 PM   #72
CanAutM3
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Quote:
Originally Posted by swamp2 View Post
When to shift is quite simple, it is not about average power nor about torque, torque is irrelevant. One shifts where the accelerative force is higher in the next gear than if the shift was not made. In other words if lines on the force vs. speed in each gear cross that shift should be made at the vehicle speed (can back calculate rpm) where they cross. Simple.
I beg to differ. Maximizing average power generated over an acceleration run is what needs to be done to optimize acceleration. Now there are several ways to calculate and figure this out and I agree that the method you suggest is one of the most straight forward ones (it is also the one I use).

The only difference between propulsive force and wheel torque is the wheel radius (this is pretty much a constant on a street cars, maybe not on a top fuel dragster though ). You need the engine torque curve and gear ratios to plot propulsive force vs road speed. Saying that torque is irrelevant is not really accurate.

You will find that when the force lines of two gears cross, the power generated in the lower gear is equal to the power generated at the higher gear at that speed. Thus maximizing average power.

Last edited by CanAutM3; 06-04-2013 at 08:14 PM..