Why is drive line power loss not a fixed amount

[sapper]

Could someone explain why the drive line componets consume a percentage of the total power and not a fixed amount. If the drive line requires X amount of energy to operate due to friction and mass, then the power loss here is a fixed amount. So what am I missing?

An example is comparing the power a car makes at sea level and then at 5000 ft. If you are in the same gear and rpms everything in the drive line is spining at the same speed at both locations. Now if power loss is figured as a percentage, then the car at sea level has more power consumed by the drive line. This does not make sense.

 

[mike69440]

The trueth about drivetrain loss.

you are partially correct.

Drivetrain loss is a complicated equation. At lower power and torque levels the % loss is greater than at higher levels. Things even will reverse at some point when the lubrication film stength goes away and material deformation occurs. (Ouch!)

For a car with the Cobra's output, using a correction factor of about 11 to 13 % is about right, not the 15% feel good number frequently touted.

Mike