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Calculator · Fuel pumpFuel pump flow requirement calculator
Injectors get the attention, but the pump decides whether they ever see their rated flow at full power. Enter your horsepower target and this tool returns the fuel volume the pump must deliver — in litres per hour — plus the pump size to actually buy once a safety margin is added.
Pump ratings are quoted at a stated pressure and voltage — compare them at your rail pressure (43.5 psi / 3 bar is typical), not at free-flow.
The formula
Total fuel (lb/hr) = HP × BSFC · Required flow (LPH) = (lb/hr ÷ 6.07 lb/gal) × 3.785 L/gal · Recommended pump = required × (1 + margin)
Assumptions, stated plainly: gasoline weighs 6.07 lb per US gallon; BSFC is 0.50 naturally aspirated and 0.60 boosted; E85 needs about 1.35× the volume for the same power. The default 25% safety margin covers the return line on return-style systems, pump ageing, voltage drop and hot-fuel days — buy the pump against the margined number, not the bare requirement.
Worked example (pre-filled above): 400 hp, naturally aspirated, gasoline: 400 × 0.50 = 200 lb/hr of fuel, which is 32.9 gal/hr or 124.7 LPH required. With a 25% margin, buy a pump good for at least 155.9 LPH at your rail pressure.
Before you order the pump
- Match the whole chain. The pump must out-feed the injectors it supplies — size the injectors first with the size calculator.
- Boosted cars need rising-rate thinking. On a boost-referenced regulator, the pump works against rail pressure plus boost, and its flow at that total pressure is the number that counts.
- Starvation shows up as duty cycle. If logged duty cycle climbs while pressure sags at high RPM, the pump — not the injector — is the limit (duty cycle calculator).
Sized them? Now service them
New injectors still need fresh seals and filters. The Universal EV1 Rebuild Kit — 200-Injector Service Tray + Removal Tool, $72.49 covers 200 injectors with matched O-rings, pintle caps and micro basket filters, and the Micro-Filter Basket Removal Tool, from $14.99, pulls the old basket filter without damage.
Free tracked USPS shipping in the US · 30-day returns · secure card checkout by Stripe · sold by Partsapiens.
Not sure which kit your injectors take? See kits by injector part number or the fitment guide.
More injector calculators
- Injector flow converter — cc/min ↔ lb/hr.
- Injector size calculator — injector size for a target horsepower.
- Max horsepower from your injectors — the reverse calculation.
- Flow rate at a different fuel pressure — the square-root rule.
- Injector duty cycle calculator — pulse width and RPM to duty %.
- Fuel pump flow requirement — LPH your engine actually needs.
Last updated October 20, 2026 · Partsapiens, 5325 Alton Pkwy, Suite C300, Irvine, CA 92604 · partsapiens@gmail.com