Various factors must be considered when selecting an electric fuel pump for an EFI system, or if you are just trying to determine whether your existing fuel pump can handle horsepower increases to the powertrain.
The most important criterion in sizing an electric fuel pump is calculating the total fuel requirement for the engine. The formula used to determine total fuel required is similar to the one used to calculate injector sizing.
Q = MAXHP x BSFC
Using a 400 HP, naturally aspirated engine with a BSFC of 0.45 four our example (.55 BSFC for turbocharged or supercharged engines), we can calculate the total fuel needed to feed this engine:
Q = 400 x 0.45 = 180 lbs/hr
Now we need to express this value in volume flow rate such as gallons per hour (gph). Divide 180 lbs/hr by 6, which is approximately the weight of 1 gallon of gasoline, and the result is 30 gph. Therefore, we need a fuel pump that can supply a minimum of 30 gph for our example engine.
The analysis is not complete. Fuel pump flow capacity decreases as fuel system pressure increases. Figure 1 shows flow curves of 2 fuel pumps at various pressures.
