Injector / Fuel Pump Sizing Calculator

Use this to calculate fuel requirements (Injector size, fuel pump capacity) from your target crank horsepower, number of injectors, and chosen fuel. Make sure to compare the target AFR versus the fuel AFR! You want a richer mixture than lambda under power!

Engine Target horsepower (crank) Number of injectors Max injector duty cycle (%)

Fuel Fuel Target AFR Fuel density (g/cc)

Choosing a fuel fills in a typical target AFR and density. You can change either one, and changing a value sets the fuel to Custom.

Fuel system Injector rating pressure (psi) Operating fuel pressure (psi) Fuel pump safety margin (%) Air per HP (lb/hp/hr)

Air per HP is how much air the engine moves for each horsepower. 6.25 is typical for a healthy engine. Use around 6.0 for an efficient build or 6.5–7.0 for a less efficient one.