[s-cars] Accurate Drive-Train Loss on UrS?

[Calvin & Diana Craig]

>Conversely, why should the driveline require more power to be spun when
>connected to a tuned motor, as opposed to a more pedestrian stock motor? It
>would seem to me that to spin the halfshafts at 60 or even 200 RPM would
>take the same effort, regardless of what HP the engine was capable of
>putting out. Rotational inertia does not factor in here, as HP is a steady
>state measurement, is it not?

Two points here:
1) Inertia does factor in.  Torque = I * Angular Acceleration.  Since HP =
Torque*RPM/5252 the higher the I, the more torque it robs.
2) However, I am along with you for the fact that the percentage is a rotten
way to say it.  It is a parasitic loss that is going to be dependent upon
Drivetrain Inertias, as well as RPM for the frictional losses.

I believe the reason you see things expressed in percentages is because in
general the larger the HP & Torque output the beefier the drivetrain needs
to be; example would be the clutch/flywheel on my '72 Pontiac vs. a Honda
Civic.  HUGE difference.  Now, if you keep the drivetrain components the
same, and then do stuff like better exhaust, more boost, etc. then the
losses should go down as a percentage.  Also, this will depend alot upon how
brute force oriented the manufacturer is to solving problems.  Example would
be using a larger gear in the tranny with thicker teeth as opposed to using
a higher strength material in the gear and keeping it small.

--Calvin