Speed Tuned Motorsports · Tech Tools
Injector Size Calculator
Dial in the right fuel injectors for your horsepower goal — instantly, in lb/hr and cc/min.
How to use this calculator
- Enter your target horsepower (crank HP, not wheel HP).
- Enter your engine's cylinder count — this assumes one injector per cylinder.
- Select your fuel and induction type; this sets the BSFC used in the formula.
- Choose a max duty cycle. 80% is the industry-standard safe ceiling — pick a lower value to leave more headroom.
Tip — Always round up to the nearest common injector size, and check with a tuner before installing injectors sized far beyond your current fuel system's capacity.
HP
CYL
Required Injector Size
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Formula