Flow Rate Conversion Convert to and from lb/hr and cc/min. Fill in either field below cc/Min Lbs/Hour 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.