Definitions of different HP and Torque measurements.
I am asked these questions quite often and thought it would be a good idea to list the answers here. Easiest definitions I found were on Wikipedia so I am just cutting and pasting. I get a few UK magazines and they are always speaking of HP in BHP and Torque in NM. So for guys who are as dumb as me this will be good stuff, for you smart ones............
Brake horsepower (bhp)
Brake horsepower (bhp) is the measure of an engine's horsepower without the loss in power caused by the gearbox, generator, differential, water pump, and other auxiliary components such as alternator, power steering, and AC compressor. Thus the prefix "brake" refers to where the power is measured: at the engine's output shaft, as on an engine dynamometer. The actual horsepower delivered to the driving wheels is less. An engine would have to be retested to obtain a rating in another system. The term "brake" refers to the original use of a band brake to measure torque during the test (which is multiplied by the engine RPM and a scaling constant to give horsepower).
(SAE)
In the United States the term "bhp" fell into disuse after the American Society of Automotive Engineers (SAE) recommended manufacturers use hp (SAE) to indicate the net power of the engine, given that particular car's complete engine installation. It measures engine power at the flywheel, not counting drivetrain losses.
SAE-certified horsepower
In 2005, the Society of Automotive Engineers introduced a new test procedure for engine horsepower and torque.[5] The procedure eliminates some of the areas of flexibility in power measurement, and requires an independent observer present when engines are measured. The test is voluntary, but engines completing it can be advertised as "SAE-certified".
hp (DIN)
DIN horsepower is the power measured according to the German standard DIN 70020 and like the SAE net figure is measured at the flywheel. However, DIN "horsepower" is often expressed in metric (Pferdestärke) rather than mechanical horsepower.
[edit] Effective horsepower (ehp) / True horsepower (thp) / Wheel Horsepower (whp)
Effective horsepower, True hp or wheel horsepower is the power converted to useful work. In the case of a road vehicle this is the power actually turned into forward motion as measured on a chassis dynamometer.
"True hp" is generally 10% to 20% less than the engine's "bhp" ratings due to drivetrain losses.
Wheel Horsepower (whp) is the more widely used term for Effective horsepower.
Some people (e.g. American automotive engineers) use horsepower (imperial mechanical) for power, foot-pounds (lbf·ft) for torque and rpm (revolutions per minute) for angular speed. This results in the formula changing to:
HORSEPOWER=Torque in ft lbs X RPM/5252
TORQUE
The SI unit for torque is newton•meters (N•m). In U.S. customary units, it is measured in foot pounds (ft·lbf) (also known as 'pounds feet').
The conversion for NM to FT LBS is:
1 newton meter = 0.737 ft. lbs.
So there's some good common numbers that get thrown around. So now if you're like me when you read anything from the UK you know the HP and torque numbers are much higher than here.
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