Real HP loss numbers

[Clarence L.Snyder]

> 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
No, Horsepower is the rate of doing work. Increasing the speed is doing
work, slowing down is negative work, and maintaining the status quo is
exactly that. It takes absolutely no power to maintain inertia - and
only a little to overcome the friction in this case. ALL power stored in
accelleration is recovered in decelleration once you factor out friction
losses.
This is why an inertia chassis dyno can so very easily if not lie, at
least mislead. It is NOT measuring horsepower, it is measuring
acceleration, from which you deduce Horsepower. Horsepower can ONLY be
actually measured under static or quasi-static (long term repeatable)
conditions, Foot Lbs/second cannot be measured at variable speeds and
variable torque (load) unless you can take a snapshot in time and
measure instantaneous speed and load. Even this is not accurate unless
multiple snapshots are taken, and an average calculated because
instantaneous torque varies with piston position, as does accelleration
and speed.
Only a load cell or an inertia cycle can determine real horsepower, and
the inertia cycle method requires considerable computational power.