So, What's The Real Transmission Power Loss %

[CSX4833]

I've heard anything from 20% to 12% on modern day manual transmission power loss at the wheel versus at the crank. There doesn't seem to be a general agreement and I realize certain variables can cause differences (e.g. altitude) but isn't there an acceptable % of loss with which one can feel comfortable stating without relying on a dyno which we all know can vary.

[KCMO-GT500]

I've heard anything from 20% to 12% on modern day manual transmission power loss at the wheel versus at the crank. There doesn't seem to be a general agreement and I realize certain variables can cause differences (e.g. altitude) but isn't there an acceptable % of loss with which one can feel comfortable stating without relying on a dyno which we all know can vary.

my 2007 was rated about 500-505 at the engine, and dynoed about 440 at the rear wheels initially. As you increase power, I am not sure that you can apply the same percentages as there are multiple areas of power loss, and I imagine some are fixed and not related to input power. Most folks just go with about 15% (for manual) and call it a day.

Edited January 19, 2014 by KCMO-GT500

[twobjshelbys]

The loss also depends on the configuration. The "parasites" like air conditioning take horsepower away before it gets to the transmission. Modern transmissions are more efficient though so the loss there will be less than it used to be. I'm surprised that transmission losses aren't actually known. They should be able to statically apply a known force to the transmission and measure how much comes out.