Injector Headroom With Nitrous Calculator

Liguori Drag Racing • Nitrous

Injector Headroom With Nitrous Calculator

Estimate injector duty and remaining capacity for engine power plus nitrous enrichment.

The 85% duty limit and BSFC values are editable examples, not universal limits or tuning recommendations. Use verified injector flow for the fuel in use; density conversion alone does not fully characterize injector behavior with a different fluid.

Fuel brandFuelFuel specific gravity (editable)

Fuel selection sets density only. Enter BSFC assumptions for your actual fuel and application.

Engine power before nitrous (crankshaft hp)Engine BSFC before nitrous (lb/hp/hr)Planned added nitrous power (crankshaft hp)Incremental nitrous BSFC (lb/hp/hr)Nitrous enrichment supplied by these injectors (%)100% for a dry system using these injectors for all added fuel; 0% when a wet system supplies all added fuel separately. Enter a split for mixed delivery.Number of identical injectorsRated flow per injectorInjector flow unitsRated injector differential pressure (psi)Actual injector differential pressure (psi)Fuel rail absolute pressure minus manifold absolute pressure. Use the pressure differential at the operating point being checked.Your maximum duty-cycle limit (%)

Results

Method and assumptions

Flow at actual pressure = rated flow × √(actual differential pressure ÷ rated differential pressure). Fuel demand = engine horsepower × engine BSFC + nitrous horsepower × incremental BSFC × EFI enrichment share. Estimated duty = demand ÷ total static injector flow × 100. cc/min converts to lb/hr using the selected fuel density.

Technical reference ↗