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The brake horsepower (bhp) is an imperial unit of measurement of power, usually in reference to the output of engines or motors, expressed in horsepower (hp). The "b" only denotes that it is measured by the resistance of an applied brake. "Brake" refers to the device which is used to provide an equal braking force to balance an engine's output force and hold it at a desired rotational speed.

Usage

In the United States, the term "bhp" fell into disuse in 1971–1972, as automakers began to quote power in terms of net horsepower in accord with standard J1349 of the Society of Automotive Engineers (SAE). SAE net horsepower is measured at the engine's crankshaft, and so does not account for transmission losses. However, similar to the DIN 70020 standard, SAE net power testing protocol calls for standard production-type belt-driven accessories, air cleaner, emission controls, exhaust system, and other power-consuming accessories. This produces ratings in closer alignment with the power produced by the engine as it is actually configured and sold.

Most countries now use the unit watt (W) and kilowatt (kW) for measurement of power. With the implementation of the EU Directive 80/181/EEC on January 1, 2010, the use of horsepower in the EU is permitted only as a supplementary unit.[1]

The term "bhp" is still used in the environment of drag racing and was adopted by Asphalt Street Storm Racing. Although the game generally displays either metric or imperial units according to the player's personal settings, the power of a vehicle is always referred to as capitalized BHP, expressed in the imperial horsepower unit.

Horsepower

Definitions

There are many different standards and types of horsepower. Two common definitions used today are the imperial horsepower (or mechanical horsepower) and the metric horsepower. In certain situations it is necessary to distinguish between the various definitions of horsepower and thus a suffix is added: hp(I) for imperial horsepower, hp(M) for metric horsepower.

Other names for the metric horsepower are the French cheval-vapeur (ch), the German Pferdestärke (PS), the Italian cavallo vapore (cv), the Polish koń mechaniczny (KM) and the Russian лошадиная сила (л. с.).

Imperial horsepower
1 hp(I) 33,000 lbf⋅ft/min

= 745.69987 W

Metric horsepower
1 hp(M) 75 kgf⋅m/s

735.49875 W

Conversion

The following table shows conversions between kW, bhp = hp(I) and the still widely used PS = hp(M). Bold numbers exact; the others are rounded to 8 digits.

Unit bhp kW PS
1 bhp (brake horsepower) 1 0.74569987 1.01386966
1 kW (kilowatt) 1,34102209 1 1,35962162
1 PS (Pferdestärke) 0.98632007 0.73549875 1

Examples

In Asphalt Streetstorm,

  • the BMW M2 Coupé's power at stock level is indicated as BHP: 365.00, which means that it has
    • 365.00 hp
    • 272.18 kW (365.00 hp · 0.74569987)
    • 370.06 PS (365.00 hp · 1.01386966)
  • the Equus Bass 770's power at stock level is indicated as BHP: 631.00, which means that it has
    • 631.00 hp
    • 470.54 kW (631.00 hp · 0.74569987)
    • 639.75 PS (631.00 hp · 1.01386966)

References

  1. Directive 2009/3/EC of the European Parliament and of the Council of 11 March 2009. Official Journal of the European Union (2009-03-11). Retrieved on 2020-09-18.
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