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Originally Posted by Lucky
Guess I should read better... 
Even so, I believe this is easily explained by the following High School Physics formula for the friction force observed between sliding surfaces:
F = mu * Fn
Where:
F = the force due to friction (loss in a tranny, for example)
mu = the coefficient of friction between two moving surfaces
Fn (as in "normal force") = the force applied perpendicular to the two moving surfaces
The key parameter above is "Fn", which inside a tranny occurs where gear surfaces touch and shafts push sideways against bearings (to counteract the torque that is spinning the shaft). As this "normal" force goes up, friction loss (F) goes up in a linear manner. So yes, the climbing loss as more power is put through a tranny makes perfect sense.
Yes, rotational inertia remains the same, but as friction loss climbs the inertia becomes less of a factor. |
Yup, the amount of friction is directly proportional to the amount of force. Rotational inertia is a very minor contributor to drivetrain losses.
If that small engine in the example is at full throttle making all of it's 100hp and the bigger engine is at part throttle, making the same 100hp, the losses in the system will be the same, but add more throttle to the big engine and friction goes up in the pistons, crank, gears, axle joints and tires.
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