What is HP anyway?

[amalventano at sc.rr.com (Allyn)]

> I know that 1 HP in electrical power=746 watts. But I see power posted as
HP
> and BHP for cars. Whats the diff? Is there any?

HP = calculated horse of engine based on torque @ rpm. there doesnt seem to
be a set standard of measurement for this one.

BHP = brake horsepower, measured at the output of the crank. 'brake' comes
from the method of measurement. engine is run wide open, at a specified rpm,
with some form of braking mechanism loading down the crank to keep it at
that rpm constantly. the amount of torque on the brake factored with rpm
gives BHP. this is the most accurate way to measure engine output, but its
not very practical since you need an engine dyno.

WHP = wheel horse, measured at wheels

WBHP = wheel horse on a 'braking dyno', where the dyno does the same as the
BHP method above, just at the wheels instead of at the crank output.

important to note is that HP/WHP figures may differ from BHP/WBHP figures.
non-braking tests may be dynamic (i.e. a dyno run, 4th gear pull, etc). in
those cases, the engine is accelerating. different factors play into this,
which may cause an engine to get higher/lower numbers as compared to the B
results.

also, dont forget european hp numbers are calculated differently sometimes.
safer to go with the kw numbers and do the conversion to us-hp to eliminate
any confusion.

hth
Al