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Engine displacement
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Engine displacement
Engine displacement is the measure of the cylinder volume swept by all of the pistons of a piston engine, excluding the combustion chambers. It is commonly used as an expression of an engine's size, and by extension as an indicator of the power (through mean effective pressure and rotational speed) an engine might be capable of producing and the amount of fuel it should be expected to consume. For this reason displacement is one of the measures often used in advertising, as well as regulating, motor vehicles.
It is usually expressed using the metric units of cubic centimetres (cc or cm3, equivalent to millilitres) or litres (l or L), or – particularly in the United States – cubic inches (CID, c.i.d., cu in, or in3).
The overall displacement for a typical reciprocating piston engine is calculated by multiplying together three values; the distance travelled by the piston (the stroke length), the circular area of the cylinder, and the number of cylinders in the whole engine.
The formula is:
Using this formula for non-typical types of engine, such as the Wankel design and the oval-piston type used in Honda NR motorcycles, can sometimes yield misleading results when attempting to compare engines. Manufacturers and regulators may develop and use specialised formulae to determine a comparative nominal displacement for variant engine types.
In several countries fees and taxes levied on road vehicles by transport authorities are scaled in proportion to engine displacement. In countries where this is practised, vehicle manufacturers often seek to increase power output through higher-revving engines or turbocharging, instead of increasing the displacement.
Examples of countries where the road taxes are based upon engine displacement:
Wankel engines are able to produce higher power levels for a given displacement. Therefore, they are generally taxed as 1.5 times[citation needed] their stated physical displacement (1.3 litres becomes effectively 2.0, 2.0 becomes effectively 3.0), although actual power outputs can be higher than suggested by this conversion factor. The nominal displacement of a Wankel engine is 3 times smaller than the physical displacement, but this is compensated by the fact that the shaft has 3 times the rotational speed of the rotor. The nominal displacement is the swept volume of a single chamber.
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Engine displacement
Engine displacement is the measure of the cylinder volume swept by all of the pistons of a piston engine, excluding the combustion chambers. It is commonly used as an expression of an engine's size, and by extension as an indicator of the power (through mean effective pressure and rotational speed) an engine might be capable of producing and the amount of fuel it should be expected to consume. For this reason displacement is one of the measures often used in advertising, as well as regulating, motor vehicles.
It is usually expressed using the metric units of cubic centimetres (cc or cm3, equivalent to millilitres) or litres (l or L), or – particularly in the United States – cubic inches (CID, c.i.d., cu in, or in3).
The overall displacement for a typical reciprocating piston engine is calculated by multiplying together three values; the distance travelled by the piston (the stroke length), the circular area of the cylinder, and the number of cylinders in the whole engine.
The formula is:
Using this formula for non-typical types of engine, such as the Wankel design and the oval-piston type used in Honda NR motorcycles, can sometimes yield misleading results when attempting to compare engines. Manufacturers and regulators may develop and use specialised formulae to determine a comparative nominal displacement for variant engine types.
In several countries fees and taxes levied on road vehicles by transport authorities are scaled in proportion to engine displacement. In countries where this is practised, vehicle manufacturers often seek to increase power output through higher-revving engines or turbocharging, instead of increasing the displacement.
Examples of countries where the road taxes are based upon engine displacement:
Wankel engines are able to produce higher power levels for a given displacement. Therefore, they are generally taxed as 1.5 times[citation needed] their stated physical displacement (1.3 litres becomes effectively 2.0, 2.0 becomes effectively 3.0), although actual power outputs can be higher than suggested by this conversion factor. The nominal displacement of a Wankel engine is 3 times smaller than the physical displacement, but this is compensated by the fact that the shaft has 3 times the rotational speed of the rotor. The nominal displacement is the swept volume of a single chamber.
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