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Brake horsepower per cubic centimeter or (bhp/cc) is a figure of merit that is used to indicate the 'state of tune' of an internal combustion engine. It is defined as the ratio of the engine's net power output to its displacement, the internal size. Power is measured at its rated speed and full throttle.
Prony brake dynamometers at a tractor contest in 1910 Schematic of a Prony brake Actual Prony Brake built for testing 5HP Steam Engine. The Prony brake is a simple device invented by Gaspard de Prony in 1821 to measure the torque produced by an engine. The term "brake horsepower" is one measurement of power derived from this method of measuring ...
However, it is the power a car can produce at the wheels (wheel horsepower or whp) that matters when it comes to acceleration performance. Wheel horsepower equals brake horsepower minus drivetrain losses, which can be anywhere from about 10% to 25%. [12] Power-to-weight ratio: hp/lb hp/lb W/kg acceleration higher is better Propulsive efficiency
Tax or fiscal horsepower is a non-linear rating of a motor vehicle for tax purposes. [19] Tax horsepower ratings were originally more or less directly related to the size of the engine; but as of 2000, many countries changed over to systems based on CO 2 emissions, so are not directly comparable to older ratings.
A compression release brake (also known as a Jacobs brake or "jake brake"), is the type of brake most commonly confused with real engine braking; it is used mainly in large diesel trucks and works by opening the exhaust valves at the top of the compression stroke, so the large amount of energy stored in that compressed air is not returned to ...
To calculate the actual efficiency of an engine requires the energy density of the fuel being used. Different fuels have different energy densities defined by the fuel's heating value. The lower heating value (LHV) is used for internal-combustion-engine-efficiency calculations because the heat at temperatures below 150 °C (300 °F) cannot be ...
For vehicles where the above formula cannot be applied (e.g. electric vehicles), the tax horsepower is derived from the effective engine power (which is defined by law as the maximum power that the engine can provide after being used at full power from 30 minutes, which is normally lower than the rated engine power).
A roller brake tester is a method of allowing the dynamic assessment of the braking system of a motor vehicle, whilst the vehicle itself is in a static condition.This type of brake tester is normally used in UK garages when used as part of an inspection lane for the MOT test.