whats the math equation to figure out crank horsepower to actual wheel horsepower. i know theres about a 25-30 percent loss from crank to whp. but how do you figure it out?

 

well, it really doesn't work that way, the number that they give you when you buy the car is one of two things, either done on an engine dyno, or done via a mathimatical equation taking into account masses and rotating ratios.

There really isn't any way to get a solid conversion, there are just way too many variables, everything from weight of flywheel, clutch, and all that, not to mention how much in the way of grinding gears could affect the equation, becuase of how much of a synchro you shave off, or something like that.

To the best of my knowledge, there is no simple conversion, and by the way, it's a lot closer to 15-25% drive train loss, the only way your really gonn have like 30% or above is with an all wheel drive car.

Later,
Aj

 

gotta agree with AJ. To toss out something a little more exact we also use 17%-18% for estimates. This is based on the 4 Integras I have owned and dyno'd the 1 Civic we used to dyno and the 2000 Prelude and 2000 CIvic SI we dyno. all fall right at 17%.