Injector-Supported Horsepower Calculator

When to use it

• Compare how a change in injector flow affects supported power before committing to parts, setup, or strategy changes.
• Check a workshop, dyno, simulator, or trackside spreadsheet result using a transparent formula: Flow × injectors × duty cycle ÷ BSFC.
• Use the result with known fuel density, measured fuel pressure, realistic duty-cycle limits, and logged lambda data. Fuel systems should be sized with headroom because demand changes with boost, temperature, fuel type, and engine safety targets.

How to use it

1. Enter injector flow in lb/hr; the default value shown is 80 lb/hr.
2. Enter injectors as a plain number; the default value shown is 4.
3. Enter duty cycle in %; the default value shown is 85 %.
4. Enter bsfc in lb/hp/hr; the default value shown is 0.55 lb/hp/hr.

How to read the result

Supported power is shown in hp. Use the number as a calculated reference point, then compare it with measured data from the car, the part supplier, or the race environment. A mathematically clean answer can still be unsuitable if the inputs are estimated, rounded, measured under different conditions, or outside the normal range for the vehicle.

Assumptions and checks

• The calculator applies the displayed formula directly and assumes the entered injector flow, injectors, duty cycle, and bsfc are valid for the vehicle and conditions being considered.
• Changing injector flow and injectors together can move the answer in ways that are easy to miss, so make related setup changes deliberately.
• Confirm the fuel type and density when converting between mass flow and volume flow.
• Keep injector duty cycle and pump capacity below their practical limits with a sensible reserve.
• Verify fuelling changes on proper measuring equipment before relying on them at full load.