In article ,
says...



I know there were at least two 'standards' of HP ratings. One was the
engine on a test stand under optimal conditions and the other was to put
the car on a dynometer and running it. That showed up all the losses in
the transmission and other things.

No, both net and gross HP are measured at the flywheel. However, net
HP was with fulll exhaust , fan installed, water pump and alternator
installed, while gross HP was a bare engine on optimized free flowing
exgaust with no fan or waterpump or alternator, and adjusted to
standard atmosphere at sea level - in other words, under "ideal"
conditions - or "theoretical" maximum HP.
Net is real world horsepower.

see:
https://ateupwithmotor.com/terms-tec...et-horsepower/
for more REAL information.


That means there are 3 ways to measure the HP in the US. It is easy for
anyone to put a car on a dyno and see what the wheel HP is but not so
easy for the 'engine ' HP where the engine is on a test stand with and
without all the items like fan belts and exhaust system with the
mufflers.

Then there is a metric HP. Not sure if the cars like Toyota and Honda
use that or not. The US is about 745 watts per HP and the metric is
about 735. That would give one a few percent advantage over the other.

Sometimes the factory just pulled the numbers out of the air. Some for
insurance pricing and some for drag racing in years past.