Drivetrain loss & WHP vs. CHP calculation discussion (read this if you want to do it right)
10-23-2006, 08:55 PM
#11
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Your first statement is correct. After that you are, as you put it "a bit off."
Drivetrain loss is based on friction in the trans, diff, tires, etc. and the inertia of the drivetrain. The firction does not change in relation to the amount of power used to accelerate the drivetrain. Inertia is directly related to mass. The inertia the engine has to overcome is determined by the mass of the drivetrain components not the output of the engine. The friction and inertia are constant so the drivetrain loss is constant.
10-24-2006, 04:25 AM
#12
The friction loss varies by road speed and/or engine speed though, right?
So if you had an engine/drivetrain combo that lost 20% to friction at its stock power peak of 5500 RPM, then tuned it so peak power was 6500 RPM, you could have a larger (in absolute terms) loss in the second case, no?
10-24-2006, 05:43 AM
#14
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Yes that's true. You would have to measure the loss at the same RPM in both cases.
The drivetrain loss will be constant at each RPM point, but it is variable as RPM increases.
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