| : I would expect that they would make in the 530RWHP range. 530*1.18 = 625 cranksaft horsepower. I've often seen people multiply the rear wheel HP numbers with the drivetrain loss the way you do, stated as 1.18 for an 18% drivetrain loss, or 1.20 for a 20% drivetrain loss. But the math does not work out that way. I'll explain. We'll use nice round numbers to make it easy. Let's say you have a 600 hp engine (crank). Let's say your tranmission has a 20% loss. Already knowing that 1/5 of 600 is 120 (a 600 hp engine would lose 120 hp through our drivetrain) we'll do the math to check to see if our calculations arrive at that answer. According to your math, a car with 500 rwhp x 1.20 would give you 600 crank hp. But we know that this cannot be right because we already know that a 600 hp engine will lose 120 hp through this transmission, and deliver 480 HP to the wheels. If we did 480 x 1.20, we'd only get 576 crank hp, which again is not right. To do the math correctly, we must multiply by a fraction. 600 x .80 = 480 This works out perfectly to give us the figure that we already know to be correct. And to calculate the other way, from RWHP to crank HP, we'd simply divide by the same fraction. 480 / .80 = 600 Perfect. Now let's plug in your numbers. 530 rwhp, with a 18% loss would be: 530 / .82 = 646.34 And to check our math, the way the teacher always taught us in school, we'd get 646.34 x .82 = 530 Perfect :-)
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