Common values: 0.45-0.50 for NA Gas, 0.55-0.65 for Turbo Gas, 0.35-0.45 for Diesel.
%
Adds extra capacity to the calculation.
Calculation Results
Mass Flow Rate (Metric)0 kg/hr
Mass Flow Rate (Imperial)0 lb/hr
Mass Flow Rate (per Second)0 g/s
Understanding Fuel Mass Flow Rate
Calculating the mass flow rate of fuel is a critical step in automotive engineering, aerospace applications, and fluid dynamics. Unlike volumetric flow (measured in gallons or liters), mass flow (measured in kilograms or pounds) accounts for the density of the fuel, which changes with temperature and fuel type. Engine Control Units (ECUs) specifically require mass flow data to determine the correct air-fuel ratio for combustion.
Method 1: The Physics Approach (Density × Volume)
The most fundamental way to calculate mass flow rate is by converting a known volumetric flow rate using the fuel's density. This is commonly used when sizing fuel pumps or measuring flow through a pipe.
Mass Flow Rate (ṁ) = Density (ρ) × Volumetric Flow Rate (Q)
For example, if a fuel pump moves 255 Liters per hour of gasoline:
Volume (Q): 255 L/hr = 0.255 m³/hr
Density (ρ): ~740 kg/m³ (Gasoline)
Calculation: 0.255 × 740 = 188.7 kg/hr
Method 2: The Engine Requirement Approach (BSFC)
When tuning an engine or sizing injectors, you often start with a power target. The mass flow rate required is determined by how efficiently the engine converts fuel into power, a metric known as Brake Specific Fuel Consumption (BSFC).
Mass Flow Rate = Target Power × BSFC
Common BSFC Values (lb/hp·hr):
Naturally Aspirated Gasoline: 0.45 – 0.50
Turbo/Supercharged Gasoline: 0.55 – 0.65
Diesel: 0.35 – 0.45
Ethanol (E85): ~30% higher than gasoline equivalents
Fuel Density Reference Table
Use these standard values for density at 15°C (59°F) if you do not have specific data sheets:
Fuel Type
Density (kg/m³)
Density (lb/gal)
Gasoline
720 – 775
6.0 – 6.5
Diesel
820 – 860
6.8 – 7.2
Ethanol (E100)
789
6.59
Methanol
792
6.61
Jet A-1
804
6.71
var currentMethod = 'vol';
function switchMethod(method) {
currentMethod = method;
var volInputs = document.getElementById('volumetricInputs');
var powerInputs = document.getElementById('powerInputs');
var btnVol = document.getElementById('btnMethodVol');
var btnPower = document.getElementById('btnMethodPower');
var resultBox = document.getElementById('resultBox');
if (method === 'vol') {
volInputs.classList.remove('hidden');
powerInputs.classList.add('hidden');
btnVol.classList.add('active');
btnPower.classList.remove('active');
} else {
volInputs.classList.add('hidden');
powerInputs.classList.remove('hidden');
btnVol.classList.remove('active');
btnPower.classList.add('active');
}
// Hide results when switching to avoid confusion
resultBox.style.display = 'none';
}
function updateDensity() {
var preset = document.getElementById('fuelPreset');
var densityInput = document.getElementById('densityVal');
if (preset.value !== 'custom') {
densityInput.value = preset.value;
// Briefly highlight to show change
densityInput.style.backgroundColor = "#e0f2fe";
setTimeout(function(){ densityInput.style.backgroundColor = "#fff"; }, 300);
}
}
function calculateFuelMass() {
var resultBox = document.getElementById('resultBox');
var kgHr = 0; // Base unit for calculation
if (currentMethod === 'vol') {
// — VOLUMETRIC CALCULATION —
var volFlow = parseFloat(document.getElementById('volFlow').value);
var volUnit = document.getElementById('volUnit').value;
var densityKgM3 = parseFloat(document.getElementById('densityVal').value);
if (isNaN(volFlow) || isNaN(densityKgM3) || volFlow < 0) {
alert("Please enter valid positive numbers for Flow Rate and Density.");
return;
}
// 1. Convert everything to Liters per Hour first
var litersPerHour = 0;
if (volUnit === 'lph') {
litersPerHour = volFlow;
} else if (volUnit === 'gph') {
litersPerHour = volFlow * 3.78541; // US Gallon to Liters
} else if (volUnit === 'ccm') {
litersPerHour = (volFlow / 1000) * 60; // cc/min to L/hr
} else if (volUnit === 'lpm') {
litersPerHour = volFlow * 60;
}
// 2. Convert Density kg/m³ to kg/L
// 740 kg/m³ = 0.74 kg/L
var densityKgL = densityKgM3 / 1000;
// 3. Calculate Mass Flow (kg/hr)
kgHr = litersPerHour * densityKgL;
} else {
// — ENGINE POWER CALCULATION —
var power = parseFloat(document.getElementById('targetPower').value);
var powerUnit = document.getElementById('powerUnit').value;
var bsfc = parseFloat(document.getElementById('bsfc').value);
var bsfcUnit = document.getElementById('bsfcUnit').value;
var margin = parseFloat(document.getElementById('safetyMargin').value) || 0;
if (isNaN(power) || isNaN(bsfc) || power < 0 || bsfc 0) {
kgHr = kgHr * (1 + (margin / 100));
}
}
// — CONVERT AND DISPLAY RESULTS —
// kgHr is our source of truth now.
var lbHr = kgHr * 2.20462;
var gSec = (kgHr * 1000) / 3600;
document.getElementById('resKgHr').innerText = kgHr.toFixed(2) + " kg/hr";
document.getElementById('resLbHr').innerText = lbHr.toFixed(2) + " lb/hr";
document.getElementById('resGs').innerText = gSec.toFixed(2) + " g/s";
resultBox.style.display = 'block';
}