quote:Originally posted by Rapier:
Lastly - to add my 2 cents.
Though it sounds logical that the losses are fixed - it's still the same transmission etc - it cannot be. This would mean producing more than 100bhp just to move the car at walking speed. There are plenty of small cars produce far less than 100bhp - could their losses be so much smaller than a ZF.
Good observation Derek,
The friction in a transmission will increase with rpm AND with power transmitted (loading).
This is why a trans oil circulation pump & oil cooler are needed when the car is raced. If the friction remained the same, no cooler would ever be needed. The fact there is more heat in the oil indicates whatever creates the heat has increased, i.e. friction.
That heat is horsepower that is lost in the transmission, the more heat (btu's), the more horsepower that is lost. The fact that high rpm & high loads create more heat in the tranny indicates these conditions also create more horsepower loss, it is not a fixed amount.
Your friend on the DTBB, George