Brake Specific Fuel Consumption (BSFC)

This is the ratio of the engine fuel consumption to the engine power output as measured at the flywheel. BSFC has units of grams of fuel per kilowatt-hour (g/kWh) or pounds mass of fuel per brake horsepower-hour (lb/bhp-hr).

BSFC is a measure of engine efficiency.

Where

η = Engine Efficiency
BSFC = Brake Specific Fuel Consumption [g kWh-1]
LHV = Lower Heating Value of fuel used by the engine [kWh g-1]

The BSFC is dependent on engine load and speed. Typically the BSFC is poor at low load, maximum load and at idle and high speed - this leaves a minimum somewhere in the centre of this map. This minimum is what is normally quoted for an engine.

Minimum BSFC Points
Turbo-prop aircraft engine at max power 295g/kWh
Turbocharged petrol car engine 245g/kWh
Turbocharged diesel car engine 205g/kWh
Large marine diesel 2-stroke 160g/kWh

Reference

P. J. Shayler, J. P. Chick and D. Eade, "A Method of Predicting Brake Specific Fuel Consumption Maps", SAE 1999-01-0556

See also: Brake Mean Effective Pressure, Brake Specific CO, Brake Specific HC, Brake Specific NOx, Fuel Consumption, Specific Fuel Consumption.

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Subjects: Automotive Engines