Combustion Efficiency - EngineKnowHow

The actual efficiency that an engine is capable of extracting the energy from a fuel due to the combustion process for useful work is known as the Combustion Efficiency or the Fuel Conversion Efficiency.   The combustion efficiency can be calculated from:







The energy content of several common fuels are:

Fuel Energy Content,    


Petrol 44
Diesel 43
Natural Gas 50
Liquefied Petroleum Gas 49
Propane 46
Methanol 20
Hydrogen 120



The table below provides examples of the combustion efficiencies for a 3L, V6, twin turbo petrol engine at different engine speed and load sites.

Engine Condition Units Part Load Maximum Torque Maximum Power
Engine Speed (rpm) 1500 4000 6500
Torque (Nm) 45 550 464
Fuel Flow (kg/hr) 3 62 94
BSFC (g/ 378 270 298
Energy Content,  Qhv
(Mj/kg) 44 44 44
Combustion Efficiency, ηc (%) 22% 30% 27%