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Fuel Injector Size Calculator

Enter your target horsepower, cylinders, BSFC and duty cycle.

How to use

  1. Enter your values in the fields above.
  2. Press Calculate to see your result instantly.
  3. Use the Share button to copy a link to your result.

About this calculator

Sizing fuel injectors correctly is one of the first steps in any engine build or forced-induction upgrade. The required injector flow rate depends on target horsepower, the engine's Brake Specific Fuel Consumption (BSFC) — how many pounds of fuel it burns per horsepower per hour — the number of cylinders sharing the load, and the maximum safe duty cycle (typically capped around 80-85% to leave headroom and avoid injector overheating).

The result is expressed in cc/min (common for aftermarket injectors) and lb/hr (common on OEM spec sheets), letting tuners and engine builders pick injectors that can supply enough fuel at wide-open throttle without running near 100% duty, which causes fuel pressure instability and lean conditions at high RPM.

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