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The efficiency of internal combustion engines depends on several factors, the most important of which is the expansion ratio. For any heat engine the work which can be extracted from it is proportional to the difference between the starting pressure and the ending pressure during the expansion phase.
Volumetric efficiency (VE) in internal combustion engine engineering is defined as the ratio of the equivalent volume of the fresh air drawn into the cylinder during the intake stroke (if the gases were at the reference condition for density) to the volume of the cylinder itself.
The efficiency often reported for a particular engine, however, is not its maximum efficiency but a fuel economy cycle statistical average. For example, the cycle average value of BSFC for a gasoline engine is 322 g/(kW⋅h), translating to an efficiency of 25% (1/(322 × 0.0122225) = 0.2540).
Consumption map of a 1.5-litre three-cylinder diesel engine. A consumption map or efficiency map [1] is a chart that displays the brake-specific fuel consumption of an internal combustion engine at a given rotational speed and mean effective pressure, in grams per kilowatt-hour (g/kWh).
Mechanical efficiency, where one form of mechanical energy (e.g. potential energy of water) is converted to mechanical energy ; Thermal efficiency or Fuel efficiency, useful heat and/or work output per input energy such as the fuel consumed; 'Total efficiency', e.g., for cogeneration, useful electric power and heat output per fuel energy ...
The following table gives the efficiency for several engines when running at 80% throttle, which is approximately what is used in cruising, giving a minimum SFC. The efficiency is the amount of power propelling the plane divided by the rate of energy consumption. Since the power equals thrust times speed, the efficiency is given by
The mean effective pressure (MEP) is a quantity relating to the operation of a reciprocating engine and is a measure of an engine's capacity to do work that is independent of engine displacement. [1] Despite having the dimension of pressure, MEP cannot be measured. [ 2 ]
Fuel efficiency is dependent on many parameters of a vehicle, including its engine parameters, aerodynamic drag, weight, AC usage, fuel and rolling resistance. There have been advances in all areas of vehicle design in recent decades. Fuel efficiency of vehicles can also be improved by careful maintenance and driving habits. [3]