# Engine power > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Engine_power > Markdown URL: https://mediated.wiki/source/Engine_power.md > Source: https://en.wikipedia.org/wiki/Engine_power > Source revision: 1342390132 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) {{Short description|Power output of an engine}} {{ Infobox physical quantity | name = Engine power | unit = [Kilowatt](/source/Kilowatt) (kW) | symbols = {{mvar|P}} | baseunits = 1000 [kg](/source/kilogramme)⋅[m](/source/meter){{sup|2}}⋅[s](/source/second){{sup|−3}} | dimension =

ML^2T^{-3}

| derivations = {{math|1=''P'' = [''M''](/source/Torque)·[''ω''](/source/Angular_velocity) }} }} '''Engine power''' is the [power](/source/power_(physics)) that an [engine](/source/engine) can develop. It can be expressed in power units, most commonly [kilowatt](/source/kilowatt), metric horsepower (often abbreviated [PS](/source/Pferdest%C3%A4rke)), or [horsepower](/source/horsepower). In terms of internal combustion engines, the engine power usually describes the ''rated power'', which is a power output that the engine can maintain over a long period of time according to a certain testing method, for example ISO 1585. In general though, an internal combustion engine has a power take-off shaft (the crankshaft), therefore, the rule for shaft power applies to internal combustion engines: Engine power is the [product](/source/Product_(mathematics)) of the engine [torque](/source/torque) and the crankshaft's [angular velocity](/source/angular_velocity). == Definition == Power is the [product](/source/Product_(mathematics)) of [torque](/source/torque) and [angular velocity](/source/angular_velocity):{{Harvnb|Böge|2017}}. p 233 Let: *

P=

Power in [Watt](/source/Watt) (W) *

M=

Torque in [Newton-metre](/source/Newton-metre) (N·m) *

n=

Crankshaft speed per [Second](/source/Second) (s⁻¹) *

\omega=

[Angular velocity](/source/Angular_velocity) =

2\pi n

Power is then: :

P= M \cdot \omega

In internal combustion engines, the crankshaft speed

n

is a more common figure than

\omega

, so we can use

2 \pi n

instead, which is equivalent to

\omega

:{{Harvnb|Fred Schäfer, Richard van Basshuysen|2017}}. p. 21 :

P= M \cdot 2 \pi \cdot n

Note that

n

is per Second (s⁻¹). If we want to use the common per Minute (min⁻¹) instead, we have to divide

n

by 60: :

P= M \cdot 2 \pi \cdot {n \over 60}

== Usage == === Numerical value equations === The approximate [numerical value equation](/source/numerical_value_equation)s for engine power from torque and crankshaft speed are:{{Harvnb|Böge|1972}}. p 154{{Harvnb|Kemp|1998}}. p 259 ==== International unit system (SI) ==== Let: *

P=

Power in [Kilowatt](/source/Kilowatt) (kW) *

M=

Torque in Newton-metre (N·m) *

n=

Crankshaft speed per Minute (min⁻¹) Then: :

P= {M \cdot n \over 9550}

==== Technical unit system (MKS) ==== *

P=

Power in [Metric horsepower](/source/Horsepower) (hp, PS) *

M=

Torque in [Kilopondmetre](/source/Kilopondmetre) (kp·m) *

n=

Crankshaft speed per Minute (min⁻¹) Then: :

P= {M \cdot n \over 716}

==== Imperial/U.S. Customary unit system ==== *

P=

Power in [Horsepower](/source/Horsepower) (hp, bhp) *

M=

Torque in [Pound-force foot](/source/Pound-force_foot) (lbf·ft) *

n=

Crankshaft speed in Revolutions per Minute (rpm) Then: :

P= {M \cdot n \over 5252}

=== Example === {{box|header=Torque and power diagram of the example diesel engine|align=right|{{Chart|definition=Diesel engine power and torque example.chart|data=Diesel engine power and torque example.tab|Width=300}}
''The power curve (orange) can be derived from the torque curve (blue)
by multiplying with the crankshaft speed and dividing by 9550.''|caption=}} A diesel engine produces a torque

M

of 234 N·m at

n

4200 min⁻¹, which is the engine's rated speed. Let: *

M= 234 \, N \cdot m

n= 4200 \, {min}^{-1} = 70 \, s^{-1}

Then: :

234 \, N \cdot m \cdot 2 \pi \cdot 70 \, s^{-1} = 102,919 \, N \cdot m \cdot s^{-1} \approx 103 \, kW

or using the numerical value equation: :

{234 \cdot 4200 \over 9550} = 102.91 \approx 103

The engine's rated power output is 103 kW. == Units == {| class="wikitable" ! ! [Kilowatt](/source/Kilowatt) ! [Kilopondmetre](/source/Kilopondmetre) per Second ! [Metric horsepower](/source/Horsepower) ! [Horsepower](/source/Horsepower) ! [Pound-force foot](/source/Pound-foot_(torque)) per minute |- ! 1 kW (= 1000 kg·m²·s⁻³) = | 1 ||''101.97'' ||''1.36''|| ''1.34'' || ''44,118'' |- ! 1 kp·m·s⁻¹ = | ''0.00980665'' || 1 || ''0.013'' || ''0.0132'' || ''433.981'' |- ! 1 PS = | ''0.73549875'' || ''75'' || 1 || ''0.986'' || ''32,548.56'' |- ! 1 hp = | ''0.7457'' ||''76.04''||''1.014''|| 1 ||''33,000'' |- ! 1 lbf·ft·min⁻¹ = | ''2.26·10⁻⁵'' || ''0.0023'' || ''2.99·10⁻⁵'' || ''3.03·10⁻⁵'' || 1 |} == See also == * [List of production cars by power output](/source/List_of_production_cars_by_power_output) == Bibliography == * {{Citation | author-link = | last = Böge | first = Wolfgang | editor = Alfred Böge | year =2017 | title =Handbuch Maschinenbau | publisher = Springer | location = Wiesbaden | language = German | isbn = 978-3-658-12528-8}} * {{Citation | author-link = | last = Böge | first = Alfred | year = 1972 | title = Mechanik und Festigkeitslehre | publisher = Vieweg | location = Wiesbaden | language = German | isbn = 9783528140106}} * {{Citation | last = Kemp | first = Albert W. | year = 1998 | title = Industrial Mechanics | publisher = American Technical Publishers | location = | language = English | isbn = 9780826936905}} * {{Citation | last = | first = | editor = Fred Schäfer, Richard van Basshuysen | year = 2017 | title = Handbuch Verbrennungsmotor | publisher = Springer | location = Wiesbaden | language = German | isbn = 978-3-658-10901-1}} ==References== {{reflist|colwidth=30em}} Category:Mechanics Category:Power (physics) Category:Engines --- Adapted from the Wikipedia article [Engine power](https://en.wikipedia.org/wiki/Engine_power) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Engine_power?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.