I was researching AWD to find out how much power the drivetrain takes up, and I ran across an interesting website, that I can't find now, but this guys concept makes total sense.

What we all believe right now is that the drivetrain takes ~20% of our power, tranny, axles, clutch, etc.

What this guy was proposing is that any given transmission and drivetrain will only take a given, specific amount of horsepower. If you think about it, it makes sense. Let me try to explain.

If we all have the same manual transmisssion and say 1 of us is non-turbo. For the sake of argument, lets say the transmission takes 28 HP (140 * 20%) to turn all the gears and axles. Now we have another guy running a 275HP turbocharged car, why would the exact same transmission, axles, etc, take any more than 28 HP to turn???

Why should the transmission take 55 HP (275 * 20%) instead of the same 25 HP it took on the NT car??

Why does the drivetrain take an extra 27 HP to turn just because the car has more power???

Shouldn't that extra 27 HP be directly applied to the wheels?

I hope this makes sense, please explain, or discuss, or ask for clarification.

I'll try to find the website I read about this on.

I see what your saying. Instead of using a percentage to attain drive train loss, it should be a constant.

Originally posted by WIDECLIPSE
I see what your saying. Instead of using a percentage to attain drive train loss, it should be a constant.

Exactly, for any given drivetrain setup.

The actual drivetrain loss may not be a percentage or a contant. It may be a more complicated function than that. But, I bet it follows more like a percentage than anything. You can assume that an appreciable amount of loss is caused by friction between the faces of the gear teeth in the transmission. The frictional forces that must be overcome will depend on the force pushing the two gear teeth surfaces together. The load put through the transmission will determine the forces pushing the gear teeth together. The load put on the transmission depends on the torque output of the engine at that time. So, higher power = higher load on gears = higher forces pushing gear teeth together = higher friction between gears = higher losses. I'm sure there is more to it than that. But that is how I picture it.

Corbin

'95 ESI-T
Now with more power and fewer leaks



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