Fuel Injector Size Calculator

Use this calculator to determine injector size.

Target Horsepower at the flywheel
Number of Injectors
B.S.F.C. *
Max Duty Cycle in % **

Injector Flow Rate @ 43.5 psi	lb/hr cc/min

* Brake Specific Fuel Consumption (BSFC) if unknown, can be estimated as .4 to .5 for naturally aspirated, and .5 to .6 for forced induction.

** For safe operation limit injector duty cycle to 80%.

Fuel Flow Calculator

Estimate changes in flow rates when a change in fuel pressure is made.

Old Fuel Pressure
New Fuel Pressure *
Old Flow Rate

New Flow Rate

Most injectors are staticaly rated at 43.5 psi. Warning; Do not change the base fuel pressure until you know how much fuel your fuel pump can supply at the new pressure. Not knowing can lead to catastrophic engine failure.