How do you calculate the transmission loss from the flywheel to the wheels. I've always thought that it was about 20% so basically if you're making 200bhp at the flywheel then it makes 160bhp at the wheels.

Is this a bit high, if so what is the approximate % loss to the wheels.

 

I thought it was generally 17% for RWD cars. I think it should be a little less for FEW cars though. Maybe 15% loss.

 

I've always wondered about this, so maybe somebody can help.

I hear that it's a percentage. Let's say 20% on a given vehicle. If the stock motor was 200HP at the crank, it would be 160HP at the wheels. Let's say we modded the motor and brought it up to 400HP at the crank. Would it be 320HP at the wheels? If so, why would it suck 40HP out of one motor and 80HP out of the other, considering that it's the same drivetrain? Maybe I'm just missing something...

 

the amount of loss will follow a negative exponential sort of curve.....you cant give it a definite percentage.....

you wont always lose the same percentage....the more driving force behind that transmission....the less of it will be devoted to turning the gears and axles....and more will be put out as horsepower......

so, as power rises, there should be less loss through the drivetrain....

17% doesnt sound right at all for RWD cars....they have a full trans, a yoke, a cv joint...a drive shaft...another cv joint....a differential then an axle....they lose a LOT to the wheels.....

upon the assumption that an average h22 puts down 170whp which is what i have gathered.....

considering that they make 200hp at the flywheel, that is also on the assumption that honda isnt lying.....which isnt entirely out of the question....

anyway, that is a 30hp loss to the ground....which comes out to 15%.....

then you take into consideration say a civic si motor....supposedly 160hp at the flywheel....but MUCH less torque than the h22......it puts like 135 to the wheels....thats a 17% loss......

so not a big difference in percentage.....maybe that is a good "rough estimate".....but if we got a good high hp flywheel vs. whp number then we could show how it decreases.....

correct me if im wrong...^^is all theory and a couple of dyno sheets....

wheel hp numbers come out to around 135 on the si.....that converts to about 17% loss

 

Firthy

Have you asked the same question on Honda Revs?

What was their reply?

 

Nope, hadn't bothered. Only asked on here because of the cam discussion but I suppose it would be a good idea.