Engine Fuel Flow Rate Calculator
Estimate required fuel pump and injector sizing based on horsepower and BSFC.
The peak fly-wheel horsepower you expect the engine to produce.
Naturally Aspirated: 0.45-0.50 | Turbo/Supercharged: 0.60-0.65
Gasoline (approx 6.07 lbs/gal)
E85 Ethanol (approx 6.59 lbs/gal)
Diesel (approx 7.00 lbs/gal)
Methanol (approx 6.60 lbs/gal)
Recommended: 15-20% extra capacity.
Please enter valid numeric values for Horsepower and BSFC.
Estimated Fuel Requirements
Mass Flow Rate:
0 lbs/hr
Volume Flow Rate (US Gallons):
0 GPH
Volume Flow Rate (Liters):
0 LPH
*Calculations include a % safety margin to ensure pump longevity and prevent lean conditions.
How to Calculate Engine Fuel Flow Rate
Calculating the fuel flow rate is a critical step when designing a fuel system for a performance engine. Whether you are upgrading a fuel pump, sizing fuel injectors, or tuning a racing engine, knowing exactly how much fuel your engine consumes at peak power is essential to prevent engine failure due to lean conditions.
The Fuel Flow Formula
The standard industry formula to determine the necessary fuel flow based on horsepower is derived from the Brake Specific Fuel Consumption (BSFC). The basic formula is:
Fuel Flow (lbs/hr) = Target HP × BSFC
To convert this mass flow into volume flow (which is how pumps are usually rated), we divide by the weight of the fuel per gallon:
Flow (GPH) = Fuel Flow (lbs/hr) / Fuel Weight (lbs/gal)
Understanding the Variables
- Target Horsepower: This is the maximum brake horsepower (bhp) you expect the engine to produce at the flywheel.
- BSFC (Brake Specific Fuel Consumption): This measures how efficiently an engine converts fuel into power.
- Naturally Aspirated Engines: Typically 0.45 to 0.50.
- Forced Induction (Turbo/Supercharged): Typically 0.55 to 0.65 (requires more fuel for cooling and safety).
- Fuel Weight: Gasoline weighs approximately 6.073 lbs per gallon, while E85 is heavier (approx 6.59 lbs/gal) and requires significantly more volume due to lower energy density.
- Safety Margin: It is standard engineering practice to size fuel systems 15-20% larger than the absolute minimum requirement to account for voltage drops, filter restrictions, and pump wear.
Example Calculation
Let's assume you are building a Turbocharged engine using Gasoline:
- Target Power: 600 HP
- BSFC: 0.60 (Typical for Turbo)
- Safety Margin: 20%
1. Base Mass Flow: 600 HP × 0.60 = 360 lbs/hr.
2. Add Safety Margin: 360 × 1.20 = 432 lbs/hr.
3. Convert to Gallons (GPH): 432 / 6.073 ≈ 71.1 GPH.
4. Convert to Liters (LPH): 71.1 × 3.785 ≈ 269 LPH.
In this scenario, you would need a fuel pump rated for at least 270 LPH to safely support your goal.