To size a fuel pump, work out how much fuel the engine needs at peak power and choose a pump that delivers that flow, plus a safety margin, at the pressure and voltage it will actually run at. Fuel required (lb/hr) = horsepower x BSFC. Dividing by the fuel’s weight, about 6.1 to 6.3 lb per gallon for gasoline, gives gallons per hour, and multiplying by 3.785 gives liters per hour, the unit most pump charts use.
Fuel pump sizing example
A supercharged engine making 500 hp with a BSFC of 0.60 needs 500 x 0.60 = 300 lb/hr of fuel. That is about 300 / 6.2 = 48 gallons per hour, or about 183 liters per hour. Adding a margin of 20 to 30 percent suggests a pump that flows around 220 to 240 liters per hour at the operating pressure.
Fuel pump size by horsepower (gasoline, approximate)
| Target power | Naturally aspirated (BSFC 0.50) | Boosted (BSFC 0.60) |
|---|---|---|
| 400 hp | About 130 L/h before margin | About 155 L/h before margin |
| 500 hp | About 160 L/h before margin | About 185 L/h before margin |
| 600 hp | About 195 L/h before margin | About 220 L/h before margin |
These come from the formula above; add margin and check the pump’s chart at your pressure.
Why pressure and voltage matter
A pump’s flow drops as pressure rises. On boosted engines with a boost-referenced regulator, rail pressure rises with boost, so the pump must deliver its flow at base pressure plus boost. Pump output also falls if voltage drops, so wiring and relays matter on high-flow systems; see fuel pressure regulator.
Sizing for E85
E85 needs roughly 30 to 50 percent more fuel for the same power, so a pump that is adequate on gasoline can run out on E85. Size for the fuel you will run; see what is E85?
In-tank, inline and dual pumps
Most modern cars use an in-tank pump, and upgrades usually replace it with a higher-flow in-tank unit. Very high power builds may add a second pump or a booster. Whatever the layout, the wiring, filter and lines must support the extra flow.
Signs a pump is too small
- Fuel pressure dropping at high rpm or under boost
- Lean codes or lean readings at the top of the rev range; see fuel trim
- Loss of power that improves at lower boost
See fuel pump symptoms and fuel injector sizing.
Complete fuel systems
For supercharged Corvettes, our ECS Stage I fuel system ($1,483.90) and ECS Stage 1 E85 fuel system ($1,832.60) are listed for late 2003 to 2013 Corvettes; see C6 Corvette supercharger kits.
More guides: how long a fuel pump lasts.
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