Real HP loss numbers

[Daniel Ciobota]

Clarence L.Snyder wrote:

> >  So, when someone is talking about a 75hp loss, not all that loss is
> friction,
> > otherwise our drivetrains would glow in the dark!  However, much of
> the loss due
> > to momentum is taken up by the engine (more strain), which shows up
> as heat in
> > the coolant and oil.
> >
> >  If my physics are wrong, please correct me.
> >
> >  Just my $0.02.
>
> The indicated horsepower on an inertia dyno may indicate this as lost
> power, but in fact it is not. In a sustained speed condition all the
> inertia effects dissapear, and when you slow down you get the power
> back. An accurate chassis dyno cannot depend on inertia alone.

 Technically, you're correct, hp required to bring all rotating mass up
to a certain speed is actually stored, and released when you let off the
gas.  But, rear wheel hp is still affected by the amount of energy you
store in the rotating assembly past the flywheel; thus, the larger the
momentum, the more energy required to bring to a certain speed, the less
energy remaining to spin the drums, thus less rear wheel hp numbers.

Daniel