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What does breaking horsepower mean?

posted by  Accord_Man

I think it means the horsepower at the crankshaft but I could be wrong

posted by  99integra

Its just horsepower at crank using a breakometer or something

posted by  CarEXPERT

Google: (and it's BRAKE, not BREAK)

BRAKE HORSEPOWER (bhp)
Definition: The measure of an engine's horsepower without the loss in power caused by the gearbox, generator, differential, water pump and other auxiliaries. The actual horsepower delivered to the driving wheels is less.

posted by  windsonian

Thank you, a to the point answer. Those are sometimes hard to come these days.

posted by  Accord_Man

I did copy and paste it out of google, so i can't take all the credit.

posted by  windsonian

Brake hp is just the same as horsepower to the crank. Of course they take all of the assesories out, thats why wheel hp is much less because the belt is driving the assessories and the engine connected to the wheel.

posted by  CarEXPERT

...and you get losses throughout the drivetrain. gear meshing, bearing wear, noise, heat etc etc ..

posted by  windsonian

Alright smartass I got a question too: If you had a car with 100hp and a car with 1000hp at the CRANK, which car would lose the most hp through the drivetrains? Is it a % of how much or what?

posted by  CarEXPERT

Hold up. BHP is horsepower measured with a friction brake. Whether that's an engine brake dyno, or a wheel one, it doesn't matter. the B in BHP has no bearing on where the measurement is taken or how many accepssories are connected.

the problem comes in that lately many websites are circulating the erroneouds definition of brake horsepower as being a type with the accessories on the engine, which is similar to the version of the term used by pump manufacturers to differntiate it from peak power. To them it's continuous power at the shaft that can be maintained over long periods of time.

But for automotive use, according the SAE, BHP is simply horsepower measured in some fashion with a brake device, like a braking dyno.

http://encyclopedia.laborlawtalk.com/Horsepower

"Brake horsepower was a term commonly used before the 1970s in the United States, and is still common in the United Kingdom. It indicates the brake, the device for measuring the true power of the engine. Stating power in 'bhp' gives some indication this is a true reading, rather than a calculated or predicted one. However, several manufacturers started to strip their engines of essential ancillaries for the purposes of getting a high horsepower figure to use in marketing the car.

In the United States the term fell into disuse after the American Society of Automotive Engineers (SAE) recommended manufacturers use "hp (SAE)" to indicate the power of the engine, given that particular car's complete engine installation. This may also be stated as "SAE net hp" or simply "net hp". The British market seemed not to need the correction. "

posted by  ChrisV

chill man ... i wasn't being a smartass, so don't get all defensive. I was just adding to your answer. It takes power to drive the accessories and you lose power from transmission losses etc.. In general most losses will be a %age (a gearbox might be typically 95% efficient or something) but as the power increases by 10 times, I'm not sure if the %age would remain constant or not.

posted by  windsonian

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