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So generally people would multiply crank hp X ~0.85 to get rwhp.

556hp X 0.85 = 472.60 rwhp

To go backwards, you divide.

472.60 rwhp / 0.85 = 556 hp

But if you dynoed your car stock at 460 rwhp, your X would be 0.8273. That is, of course, assuming your engine actually puts out exactly 556 crank hp.

To sum it up, you can really only make an educated guess.

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The rear wheel HP given in many discussions is taken from dynamometer readings. So, to get to the flywheel HP, add the drive train loss (if you know it) to the rear wheel HP.

If this is an educated guess, then i take it that all companys put out higher hp numbers then whats acually there, so that they can one up their competitors. To bad everyone doesn't go by the rwhp. Thanks for the info. Cecil..........

So generally people would multiply crank hp X ~0.85 to get rwhp.

556hp X 0.85 = 472.60 rwhp

To go backwards, you divide.

472.60 rwhp / 0.85 = 556 hp

But if you dynoed your car stock at 460 rwhp, your X would be 0.8273. That is, of course, assuming your engine actually puts out exactly 556 crank hp.

To sum it up, you can really only make an educated guess.

Automatics can be 15-18% drivetrain loss.

All wheel drive also causes drivetrain loss.

I guess we just need a little compilation of stock dyno runs and we can calculate what the drivetrain loss is on automatics and manuals for these cars.

If you mean all companies as in GM, etc, no they don't make an educated guess. they have engine dynos that dyno the actual flywheel horsepower. They do this with the engine out of the car. I know for my Z06, they dyno'd each engine to make sure it was @ 505HP. Then again those motors were hand built.If this is an educated guess, then i take it that all companys put out higher hp numbers then whats acually there, so that they can one up their competitors. To bad everyone doesn't go by the rwhp. Thanks for the info. Cecil..........

Mark

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