Editing Engine (section)

== Performance ==
The following are used in the assessment of the performance of an engine.

=== Speed ===
Speed refers to crankshaft rotation in piston engines and the speed of compressor/turbine rotors and electric motor rotors. It is typically measured in [[revolutions per minute]] (rpm).

=== Thrust ===
[[Thrust]] is the force exerted on an airplane as a consequence of its propeller or jet engine accelerating the air passing through it. It is also the force exerted on a ship as a consequence of its propeller accelerating the water passing through it.

=== Torque ===
[[Torque]] is a turning [[Moment (physics)|moment]] on a shaft and is calculated by multiplying the force causing the moment by its distance from the shaft.

=== Power ===
[[Power (physics)|Power]] is the measure of how fast work is done.

=== Efficiency ===
{{Main|Engine efficiency}}
Efficiency is a proportion of useful energy output compared to total input.

=== Sound levels ===
Vehicle noise is predominantly from the engine at low vehicle speeds and from tires and the air flowing past the vehicle at higher speeds.<ref>{{cite journal|first=C. Michael |last=Hogan |title=Analysis of Highway Noise |journal=Journal of Water, Air, and Soil Pollution |volume=2 |issue=3 |pages=387–92 |date=September 1973 |issn=0049-6979 |doi=10.1007/BF00159677 |bibcode=1973WASP....2..387H |s2cid=109914430 }}</ref> Electric motors are quieter than internal combustion engines. Thrust-producing engines, such as turbofans, turbojets and rockets emit the greatest amount of noise due to the way their thrust-producing, high-velocity exhaust streams interact with the surrounding stationary air.
Noise reduction technology includes intake and exhaust system [[muffler]]s (silencers) on gasoline and diesel engines and noise attenuation liners in turbofan inlets.