Why is the power of a car called BRAKE HORSE POWER ?

Answer 1

I think some of the other people answering this quesiton are confused... you are asking specifically about "brake" horse power, not about simply what horse power is, right?

BHP is the output of the engine WITHOUT the loss of power resulting from accessories that it drives. That's why hp that makes it to the wheels of the vehicle is always significantly less, because some power gets lost due to the added stress. The actual term "brake," as I just learned from my good friend Wikipedia, comes from an old tool used to test engine power called a band brake.

Answer 2

It is called "horse power" as engines (going back to the early days of steam) were originally used to replace horses, and a 2hp engine could do the same amount of work in a set amount of time as 2 horses.
The "brake" part comes from the machinery (a "band brake"once used to measure it - basically the engine was made to work against a brake, and the power measured by the amount of braking necessary to hold the engine at constant speed.

Some band brakes are still in use (my university had one for undergraduate laboratory use in the mid 90s), but engine development centres now use electrical dynamometers to measure an engine's output.

Answer 3

In the 70's and 80's the BHP used to be measured on a resistance in ideal conditions, it was usually prefaced with the letters SAE. Now it's DIN and typically the BHP figure is that taken at the back wheels although manufacturers are still tending to exaggerate that figure quite a bit - there's a magazine, EVO, that from time to time will put cars' back wheels on the current version of the 'brake' just to check and some of them, are miles out.

Answer 4

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.

Brake hp is usually much more than rear wheel or front wheel hp due to friction loss through the accesories(tranny, gears,etc. Make the car seem more powerful than it really is in advertising I.E. Ford GT Mustang 303bhp, 247 at the rear wheels.

Answer 5

At the beginning of the automotive industries cars were rated against horses as a way for people of the time to understand the power of the cars.

Answer 6

Its relative to the power , one horse pulling one cart and so on 2 horses and so on back in the days before engines

Answer 7

because horse power is no longer figured out by how much a horse can pull but instead they hook up the engine to a machine that tries to stop the engine by not allowing the drive shaft to turn
recently they use the drive shaft to spin a huge magnetic that creates an emf then they measure that using sensors

Answer 8

I understand the HORSE POWER bit.
But Why the BRAKE ?
Surely this relates to slowing down / Decelleration ?

Answer 9

'Brake Horse Power' was the slogan used by protesters in the days when we were ruled by horses. Thankfully the horses relinquished their power fairly peacefully.

Answer 10

BHP takes into consideration all the accessories attached to the engine, power steering, A/C, alternator, transmission or any other power robbing accessories attached to the motor. If those weren't part of the equation the horsepower numbers would be inflated.