Quote:
Originally Posted by cfg83
Gasoline with 250 g/kW·h BSFC :
1 / ( 250 * 0.0122225)
= 1 / ( 250 in g/kW·h * 0.0122225 in kW·h/g )
= 1 / 3.055625
= 0.32725 "efficiency"
Is this the way it's supposed to be? Are there units for this?
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That's correct; your end result is the percentage. In your calculation the engine is 32.725% efficient, with percentages being unitless ratios.
Note that diesel has lower heat energy per pound than gasoline. Diesel fuel is 7.1 lb/gal density whereas gasoline is just over 6 lb/gal. Diesel has more energy per gallon as a result, yet less energy per pound. Diesel engines with comparable BSFC ratings as a gasoline counterpart are therefore more "fuel efficient" in a L/100km or MPG aspect despite requiring equal energy per power output.