Fuel Pump Sizing
Enter your peak horsepower goal at the flywheel/crank.
Naturally Aspirated (NA)
Forced Induction (Turbo/Supercharger)
Gasoline (Pump Gas/Race Gas)
E85 (Ethanol)
Methanol
Recommended: 15-20% to avoid running pump at 100% duty cycle.
Estimated BSFC Used:
0.50
Fuel Mass Flow:
0 lbs/hr
Flow Rate (US Gallons):
0 GPH
Required Flow Rate (Liters):
0 LPH
*Calculation assumes standard system pressure (approx 43.5 PSI / 3 Bar). Increasing base pressure reduces pump volume.
How to Calculate Fuel Pump Size Requirements
Choosing the correct fuel pump is critical for engine performance and reliability. An undersized pump leads to lean conditions, which can cause catastrophic engine failure, especially in forced induction applications. This calculator helps you determine the minimum flow rate required to support your target horsepower.
Understanding Brake Specific Fuel Consumption (BSFC)
The core of fuel system sizing is BSFC, which represents how efficiently an engine converts fuel into horsepower. It is measured in pounds of fuel per horsepower per hour (lbs/hp/hr). Different engine configurations have different efficiency levels:
- Naturally Aspirated (Gasoline): Efficient engines typically use ~0.45 to 0.50 lbs of fuel per HP.
- Turbo/Supercharged (Gasoline): Forced induction generates more heat and requires richer mixtures, typically needing ~0.60 to 0.65 lbs per HP.
- E85 & Methanol: These fuels have lower energy density than gasoline, requiring significantly more volume (approx 30% more for E85 and 100% more for Methanol) to make the same power.
The Math Behind the Calculator
To calculate the required flow rate, we use the following standard formulas:
1. Determine Total Fuel Mass Required:
Lbs/Hr = Target HP × BSFC
2. Convert Mass to Volume (Gallons):
GPH = Lbs/Hr ÷ Fuel Weight (lbs/gal)
(Gasoline ≈ 6.0 lbs/gal, E85 ≈ 6.6 lbs/gal)
3. Convert to Industry Standard (Liters):
LPH = GPH × 3.785
Safety Margins and Duty Cycle
You should never size a fuel pump to run at 100% capacity continuously. As fuel pressure rises (common in boosted applications with a 1:1 regulator), fuel pump flow decreases. Additionally, voltage drops and clogged filters can reduce flow.
We recommend a Safety Margin of 15-20%. If your engine mathematically needs 200 LPH, you should install a pump capable of at least 240 LPH to ensure the fuel rail pressure remains stable under peak load.
Common Fuel Pump Sizes
- 255 LPH: Standard upgrade for street cars (up to ~500HP on gas).
- 340 LPH: High-performance single pump (up to ~700HP on gas).
- 450/525 LPH: "Walbro 450/Hellcat" style pumps for E85 and high boost (700HP+).