break horsepower

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if a engine has a 20bhp what is the hp of this motor????

posted by  johnp0154

Very little.

posted by  DodgeRida67

Go to the Gearhead Garage... That'll answer some questions.. :thumbs:

posted by  R34RB30DETTV

Actually johnp0154, it is "BRAKE Horsepower" and not "Break Horsepower" to imply a load placed on something rather than to break something by damaging it. BHP is the acronym and it means:

as per dictionary.com:
"The actual or useful horsepower of an engine, usually determined from the force exerted on a friction brake or dynamometer connected to the drive shaft."

This means that BHP is the actual USEFUL power rating that we care about. If that motor you were talking about was 20BHP, that means that it is capable of 20 useful horsepower to accomplish some level of work that it was employed to do. It is basically FINAL power rating and therefore the rating we care about.

This would be like rear wheel horsepower of a car's engine capability. If you have a 1971 Chevelle SS 396 and the engine is putting out 400 horsepower from the crankshaft, we don't care about that because WE CARE about the fact that once that power is transfered through the driveline (transmission to the driveshaft and through the rear differential to the rear tires) we now have 380BHP, say. The horsepower of that car is 380BHP (useful horsepower). We've lost the other 20HP mainly to frictional losses and heat/noise as well...so who cares about that 20HP. It is gone. Does that answer your question? :smoke:

posted by  cmeseadoin

Again I get the chance to say, HUH? While you are correct about power loss through the drivetrain, that has nothing to do with the term 'brake horsepower'. You are guilty of "D". I know I've answered this previously but here goes again.



SAE Gross Horsepower or Brake horsepower (bhp) was the standard horsepower measurement by the automotive industry up until 1971. Brake Horsepower Power is measured at the flywheel with no load from a chassis or any accessories and with fuel and ignition operations under ideal conditions. An accessory is anything attached to the engine, by any means, which is not required for basic engine operation. By this definition, this would include a power steering pump, smog pump, air conditioning compressor and an alternator. Ideal conditions, often called laboratory conditions, are standardized settings for use during horsepower measurement. During the 1960s they consisted of a barometric pressure of 29.92 Hg and a temperature of 60 degrees F.

SAE Net Horsepower became the standard measurement in 1972, and is still used today. SAE Net horsepower is the horsepower generated by the engine at the flywheel with all accessories attached. This change was made to reflect the numerous energy sapping accessories that cars began to have, such as an A/C Compressor and alternator, and thus was a better representation of the actual power generated by the engine. This number is always lower than the SAE Gross horsepower. Therefore, the same engine could have been rated in 1971 as 360 SAE Gross Horsepower and in 1972 as 300 SAE Net horsepower without any reduction in "power."

posted by  vwhobo

OHHHHHHHHHHHHHH LOOK, I am guilty! :hi: Logically though, if the definition of BHP is the "useful" amount of power from an engine....that is final drive power to me. I could not care less about what the engine has at the crank, rather, I want to know what it has at the rear wheels via driveline losses with an automobile.

I still read horsepower ratings in mags and such very often that speak in terms of BHP. If SAE has a new standard, why is it still printed.

I guess I'm just GUILT as charged, spank me! :laughing: :orglaugh:

posted by  cmeseadoin

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