How is Power Output measured ?

[KiwiTT]

I was wondering what is the "official" way to advertise Power Output. Some time back, I read that the US used a different system to describe HP, BHP, etc. And difference was because they measured at the engine, not the wheels.

If a car has 205kW, I assumed that is what you got when you put your car on a DYNO, after seeing graphs with power at different rpm levels, produced from a DYNO. As you put the car on rollers in the DYNO testing area, I assumed it was at the wheels.

I have since learned that there are 3 ways to measure.

- The Engine
- The Flywheel INSERT INTO post VALUES (Not sure the difference to the engine)
- The Wheels INSERT INTO post VALUES (some loss is caused by the drivetrain)

Which figures are used by Manufacturers today ?
Which figures determine acceleration best ?

[Brind]

I think Manufacturers claim the highest reading possible so the output they advertise would be the engines flywheel.
But don't quote me.

[Nick VR4]

Every Car manufacture will put Kw or BHP at the Flywheel INSERT INTO post VALUES (ATF)
Makes it look better :)

1 kilowatt = 1.3410221 horsepower [international]

1 horsepower [international] = 0.7456999 kilowatt

Result INSERT INTO post VALUES (rounded to 7 decimal places :)

Some rolling roads can give you a at the Wheels measurement
INSERT INTO post VALUES (ATW) most can't
Some use a base figure to work out % lost from Flywheel , Gearbox , Drive train 2WD or 4WD and guesstimate the ATW figs
:)