# Brake horsepower and relationship

### Horse Power: What is Horse Power? How to Calculate it? And, How to use it effectively?

Horsepower (hp) is a unit of measurement of power There are many different standards and .. Boiler horsepower is abbreviated BHP, not to be confused with brake horsepower, below, which is also abbreviated BHP. . psi (48 kPa) and for the piston speed to be that generated by the assumed relationship for paddle ships. HP vs BHP. You are bound to have stumbled upon the term Horsepower, whether you own a vehicle or not. HP is a measurement which is. A common motoring question is, 'what is the difference between horsepower, brake horsepower and metric horsepower?'. It is not unreasonable to wonder.

Technology Torque and BHP explained Most people have some idea of what an engine's power is, but are hazy about exactly what the torque figure represents. In fact, many cars that feel powerful are showing the effects of strong torque rather than high power output. Most people have some idea of what an engine 's power is, but are hazy about exactly what the torque figure represents.

Measuring engine torque and power Measuring engine torque and power An engine's power is measured by running the engine against a load on a dynamometer. The braking effort needed to hold the engine at a steady speed on full throttle gives the torque.

The power can then be calculated by multiplying the torque by the engine speed. An engine which produces a lot of torque over a wide range of engine speeds will be relaxing to drive because fewer gearchanges are needed: At cruising speeds a lorquey' engine will not need to be turning over very quickly because it can pull at high gearing, which makes for good economy. Engines that produce a lot of power for their size do not usually produce so much torque, and what torque there is is often produced at higher engine speeds.

It is also likely that the engine will be producing usable torque and power over a smaller range of engine speeds; this narrow 'power band ' makes the engine less suitable than a torquey or 'lazy' engine for jobs such as towing, and the car will be less relaxing to drive. Typical figures A fairly typical small family car engine puts out, say, 60bhp brake horse power at rpm.

The same engine can be tuned or modified so that it gives 80bhp at rpm.

### Horsepower - Wikipedia

But although the power is greater, the peak torque can actually be less, as well as occurring at a higher engine speed. Brake refers to the device which was used to load an engine and hold it at a desired rotational speed. During testing, the output torque and rotational speed were measured to determine the brake horsepower.

Horsepower was originally measured and calculated by use of the "indicator diagram" a James Watt invention of the late 18th centuryand later by means of a Prony brake connected to the engine's output shaft.

More recently, an electrical brake dynamometer is used instead of a Prony brake.

Although the output delivered to the drive wheels is less than that obtainable at the engine's crankshaft, use of a chassis dynamometer gives an indication of an engine's "real world" horsepower after power losses in the drive train and gearbox.

Shaft horsepower[ edit ] Shaft horsepower shp is the power delivered to a propeller shaft, a turbine shaft — or to an output shaft of an automotive transmission.

## Horse Power: What is Horse-Power? How to calculate and use it effectively?

Shaft horsepower is a common rating for jet engines, industrial turbines, and some marine applications. Reciprocating internal-combustion automobile engines are rated instead in the US by SAE certified net power, which is measured at the engine's crankshaft, and so does not account for losses in the transmission.

Equivalent shaft horsepower eshp is sometimes used to rate turboprop engines. It includes the equivalent power derived from jet thrust. The vehicle is generally attached to the dynamometer and accelerates a large roller and Power Absorbing Unit which is driven by the vehicle's drive wheel s.

The actual power is then computer calculated based on the rotational inertia of the roller, its resultant acceleration rates and power applied by the Power Absorbing Unit.

## Torque and BHP explained

Some motor vehicle and motorbike dynamometers can also be purely inertia-based where the power output is calculated from measuring the acceleration of a roller drum with a known rotational inertia and known parasitic frictional losses of the roller drum's bearings. Engine power test standards[ edit ] There exist a number of different standard determining how the power and torque of an automobile engine is measured and corrected.

BHP is measured within the engine's output shaft, and was originally designed to calculate and compare the output of steam engines. The horsepower was a widely adopted unit to measure the output of turbines, piston engines, electric motors, and other machinery. It is a very important unit for airplane engines and turbines.

It helps the proper calculation of an engine's efficiency, in order to ensure its smooth working between the take off and landing of a flight. History The term 'horsepower' was coined by James Watt, for efficient marketing of his improved steam engine. It was used to compare the power of a horse with that of a steam engine.