Fuel Mass Flow Rate Calculation

Fuel Mass Flow Rate Calculator

This calculator determines the required fuel mass flow rate based on engine power targets and Brake Specific Fuel Consumption (BSFC). This is essential for sizing fuel pumps, injectors, and lines for high-performance and industrial engine applications.

Fuel System Requirements

Enter peak horsepower at the flywheel.

Naturally Aspirated: ~0.45-0.50 | Turbo/Supercharged: ~0.60-0.65

Gasoline (6.07 lb/gal) Diesel (7.00 lb/gal) E85 Ethanol (6.59 lb/gal) Methanol (6.60 lb/gal) Avgas 100LL (5.85 lb/gal)

Please enter valid numeric values for Power and BSFC.

Required Fuel Flow

Mass Flow Rate (Imperial): –

Mass Flow Rate (Metric): –

Volumetric Flow (GPH): –

Volumetric Flow (LPH): –

*Safety Margin Note: When sizing fuel pumps, it is recommended to add 20-30% overhead to these calculated figures to account for system efficiency losses and future upgrades.

function calculateFuelFlow() { // Get inputs by ID var hp = document.getElementById('enginePower').value; var bsfc = document.getElementById('bsfcInput').value; var density = document.getElementById('fuelDensity').value; var errorDiv = document.getElementById('errorMsg'); var resultsDiv = document.getElementById('resultsArea'); // Convert to floats var hpVal = parseFloat(hp); var bsfcVal = parseFloat(bsfc); var densityVal = parseFloat(density); // Validation logic if (isNaN(hpVal) || isNaN(bsfcVal) || hpVal <= 0 || bsfcVal <= 0) { errorDiv.style.display = 'block'; resultsDiv.style.display = 'none'; return; } // Hide error if valid errorDiv.style.display = 'none'; resultsDiv.style.display = 'block'; // Calculations // Formula: Mass Flow (lb/hr) = HP * BSFC var massFlowLbHr = hpVal * bsfcVal; // Formula: Mass Flow (kg/hr) = lb/hr * 0.453592 var massFlowKgHr = massFlowLbHr * 0.453592; // Formula: Volumetric Flow (gal/hr) = Mass Flow (lb/hr) / Density (lb/gal) var volFlowGalHr = massFlowLbHr / densityVal; // Formula: Volumetric Flow (L/hr) = gal/hr * 3.78541 var volFlowLHr = volFlowGalHr * 3.78541; // Update DOM with results (formatted to 2 decimal places) document.getElementById('resMassLb').innerHTML = massFlowLbHr.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}) + " lbs/hr"; document.getElementById('resMassKg').innerHTML = massFlowKgHr.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}) + " kg/hr"; document.getElementById('resVolGal').innerHTML = volFlowGalHr.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}) + " GPH"; document.getElementById('resVolLiters').innerHTML = volFlowLHr.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}) + " LPH"; }

What is Fuel Mass Flow Rate?

Fuel mass flow rate ($\dot{m}$) is the measurement of the mass of fuel traveling through a fuel system over a specific period. Unlike volumetric flow rate (measured in gallons or liters), mass flow rate (measured in lbs or kg) is not affected by temperature or pressure changes that alter fuel density, making it the most accurate metric for tuning engines and sizing fuel injectors.

Formulas Used in Calculation

This calculator utilizes the Brake Specific Fuel Consumption (BSFC) method, which is the industry standard for estimating fuel requirements based on engine power output.

• Mass Flow Rate (lbs/hr) = Horsepower (HP) × BSFC (lb/hp-hr)
• Volumetric Flow Rate (GPH) = Mass Flow Rate (lbs/hr) ÷ Fuel Density (lb/gal)

Understanding BSFC (Brake Specific Fuel Consumption)

BSFC measures how efficiently an engine converts fuel into power. Lower numbers indicate higher efficiency. Accurate inputs are critical for the calculator:

• Naturally Aspirated Engines: Typically use a BSFC between 0.40 and 0.50.
• Turbocharged/Supercharged Engines: Typically use a BSFC between 0.55 and 0.65 (running richer for cooling and detonation prevention).
• Methanol/Ethanol: These fuels have lower energy density, requiring significantly higher mass flow rates (effectively doubling the BSFC value compared to gasoline in some contexts).

Why Calculate Fuel Mass Flow?

Correctly calculating mass flow rate is vital for:

1. Fuel Pump Sizing: Ensuring your fuel pump can supply enough volume at the required pressure to support peak horsepower.
2. Injector Sizing: Selecting injectors that can deliver the required mass flow without exceeding 80-90% duty cycle.
3. Return Line Sizing: Ensuring the return line is large enough to handle the flow when the engine is at idle (low consumption).