Difference between horsepower and brake horsepower?

Question

This has confused me for a while..and the internet was useless for searching this.

Answer 1

The answer to this does depend on how long back in time you consider in the context of "cars and transportation". Many many years ago cars were labelled as 8, 10, 14 or 16 horsepower relating to simple engine capacity at 10 horsepower per litre. So a classic car rated at 14 hp had more or less a 1400 cc engine. In those days we used to talk about long stroke, short stroke or square stroke as well which related to the ratio of cylinder bore to stroke. Long stroke engines didnt rev so easily but did pull better with higher torque. Short stroke engines revved higher but suffered from lower torque. Nowadays it is useless to compare such specifications and the mechanical world has standardised to measure the bhp and torque of engines (at various engine speeds) as true representation of an engines power output. Some answers are correct in that you measure brake horsepower by applying some sort of brake effect to absorb the power output. You can measure bhp and torque at the crankshaft or at the wheel which either takes account of the transmission or doesnt. Try looking up power curves for some motors on the internet and you find with modern electronic engine management you can get varying power output out of the same engine by changing the engine management settings. You can also change the shape of the power/torque curve to give more driveability in everyday use. My Triumph bike will deliver 120 bhp if I take the revs up which is awesome power on a 200 kg machine but you dont drive around at max power all the time. On the other hand my turbo diesel car is rated at 100 bhp but the real power comes from the torque between 1500 and 2500 rpm.

Answer 2

The definition of 1 horsepower is the ability to raise 550 pounds 1 foot high in 1 second. Another way of saying that is “550 foot-pounds per second”.

Brake horsepower is the vehicle’s horsepower measured where the power is delivered (for example, at the rear axle of a truck tractor. Shaft horsepower is the power measured at the engine itself, before any losses from the clutch or differential occur.

So the only real difference is where it's measured. If you measure at the engine output, you can claim high numbers. But what matters is what is delivered to the tires. There is obviously some loss through the gears, etc. so brake horsepower is the more honest number.

Answer 3

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. 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).

http://en.wikipedia.org/wiki/Horsepower#Brake_horsepower_.28bhp.29

ADDED:
They're basical the same. Just measured in a different manner.

Answer 4

Horsepower used to be measured on an engine with no accessories (allternator, power steering, torque convert not hooked up. Brake horsepower is measured WITH all of that hooked up. 'Raw' horsepower is made by very powerful engines like the old big block 427 Chevys and 426 Hemis, brute strength and tons of torque to burn tires and tear out clutches, transmissions and rear ends. The ultimate desire for maximum high performance. Lots of fun, too. Nothing quite like blowing a competitor's doors off!

Answer 5

BRAKE HORSEPOWER is the actual amount of power that an engine can deliver at a certain speed with a wide-open throttle. The term brake horsepower is derived from the braking device (usually a dynamometer) that is applied to measure the horsepower an engine develops. The dynamometer consists of a resistance-creating device, such as an electric armature revolving in a magnetized field. A paddle wheel revolving in a fluid may also be used to absorb the energy.

Horsepower is defined as work done over time. The exact definition of one horsepower is 33,000 lb.ft./minute. Put another way, if you were to lift 33,000 pounds one foot over a period of one minute, you would have been working at the rate of one horsepower. In this case, you'd have expended one horsepower-minute of energy.

Answer 6

Horsepower rating is the gross horsepower w/o accessories draining power, as on a "stand " type dynamometer. Brake horsepower rating is the net horsepower at the rear wheels as measured on a chassis dynamometer. Usually the net is 20-25% lower depending on accessories & transmission type. An automatic trans will lose more than a manual trans, for example.

Answer 7

Horsepower is the power output of the engine, when in neutral gear and not driving anything.

Brake horsepower is the power measurement at the wheels, that is the useful power. Power between the engine and the wheels will be lost in turning the drive shaft, gearbox etc.

So horsepower is the output of engine. Brake horsepower it the power at the wheels, the actual driving power.

Hope that helps, can't explain it any other way anyway, I'm just a dumb blonde

Answer 8

nothing really just a difference in output areas.