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Drivetrain Efficiency

I'm sure we're all familiar the terms HP@Crankshaft and HP@Wheel.

When we measure HP using common Dyno machines, we are measuring the
HP@Wheel. Then, using an approximation constant, we approximate the actual
HP@Crank.

I've never been into any Dyno shop, so correct me if I'm wrong. From what
I've heard, HP@Wheel = .85 HP@Crank. (approximation) For automatic trans,
it's more like HP@Wheel= .80 HP@Crank.

The constant (.85, or .80) comes from the energy loss through the
driveshaft(Is this the proper word to use??). Well, my question is do people
actually measure the different driveshaft efficiency on different cars??
In another word, different cars should have different efficiency. Different
set ups (Front wheel, Rear wheel, All wheel Drive), or different material
used. (I heard either 944 or 928 has fiber reinforced aluminum shaft).

So, maybe in a Ferrari, HP@Wheel = .9 HP@Crank. (You get the idea)

Anybody wants to toss in their $.02?



Michael Ting
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