.emfr-calculator-box {
background: #f8f9fa;
border: 1px solid #e9ecef;
border-radius: 8px;
padding: 30px;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
margin-bottom: 40px;
}
.emfr-input-group {
margin-bottom: 20px;
}
.emfr-input-group label {
display: block;
margin-bottom: 8px;
font-weight: 600;
color: #2c3e50;
}
.emfr-input-group input, .emfr-input-group select {
width: 100%;
padding: 12px;
border: 1px solid #ced4da;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
}
.emfr-input-group input:focus {
border-color: #4dabf7;
outline: none;
box-shadow: 0 0 0 3px rgba(77, 171, 247, 0.25);
}
.emfr-grid {
display: grid;
grid-template-columns: 1fr 1fr;
gap: 20px;
}
@media (max-width: 600px) {
.emfr-grid {
grid-template-columns: 1fr;
}
}
.emfr-btn {
background-color: #0056b3;
color: white;
border: none;
padding: 15px 30px;
font-size: 18px;
font-weight: bold;
border-radius: 4px;
cursor: pointer;
width: 100%;
transition: background-color 0.2s;
}
.emfr-btn:hover {
background-color: #004494;
}
.emfr-results {
margin-top: 30px;
background-color: #fff;
border: 1px solid #dee2e6;
border-radius: 6px;
padding: 20px;
display: none;
}
.emfr-result-item {
display: flex;
justify-content: space-between;
align-items: center;
padding: 10px 0;
border-bottom: 1px solid #eee;
}
.emfr-result-item:last-child {
border-bottom: none;
}
.emfr-result-label {
font-weight: 500;
color: #495057;
}
.emfr-result-value {
font-weight: 700;
color: #212529;
font-size: 1.1em;
}
.emfr-highlight {
background-color: #e7f5ff;
padding: 15px;
border-radius: 5px;
margin-top: 10px;
border: 1px solid #d0ebff;
}
.emfr-highlight .emfr-result-value {
color: #0056b3;
font-size: 1.4em;
}
.emfr-article h2 {
color: #2c3e50;
margin-top: 30px;
border-bottom: 2px solid #eee;
padding-bottom: 10px;
}
.emfr-article p {
line-height: 1.6;
margin-bottom: 15px;
}
.emfr-article ul {
margin-bottom: 20px;
line-height: 1.6;
}
function calculateExhaustFlow() {
// 1. Get Input Values
var dispL = document.getElementById('engineDisp').value;
var rpm = document.getElementById('engineRPM').value;
var ve = document.getElementById('volEff').value;
var tempC = document.getElementById('intakeTemp').value;
var pressureBar = document.getElementById('mapPressure').value;
var afr = document.getElementById('afr').value;
var cycle = document.getElementById('engineCycle').value;
// 2. Validate Inputs
if (dispL === "" || rpm === "" || ve === "" || tempC === "" || pressureBar === "" || afr === "") {
alert("Please fill in all fields to calculate the flow rate.");
return;
}
// Convert strings to numbers
var D_liters = parseFloat(dispL);
var N_rpm = parseFloat(rpm);
var VE_percent = parseFloat(ve);
var T_celcius = parseFloat(tempC);
var P_bar = parseFloat(pressureBar);
var AFR_val = parseFloat(afr);
var strokes = parseFloat(cycle);
if (D_liters <= 0 || N_rpm <= 0 || VE_percent <= 0 || P_bar <= 0 || AFR_val <= 0) {
alert("Inputs must be positive numbers.");
return;
}
// 3. Perform Calculations
// Constants
var R_specific = 287.05; // J/(kg*K) for dry air
// A. Calculate Air Density (rho)
// Convert Pressure to Pascals (1 Bar = 100,000 Pa)
var P_pa = P_bar * 100000;
// Convert Temp to Kelvin
var T_kelvin = T_celcius + 273.15;
// Density (kg/m^3) = P / (R * T)
var density = P_pa / (R_specific * T_kelvin);
// B. Calculate Theoretical Volume Flow (m^3/s)
// Displacement in m^3 = Liters / 1000
var D_m3 = D_liters / 1000;
// Revolutions per second = RPM / 60
var rps = N_rpm / 60;
// Intake strokes per second: For 4-stroke = RPS / 2, For 2-stroke = RPS
var intakeStrokes = (strokes === 4) ? (rps / 2) : rps;
var volFlow_m3s_theoretical = D_m3 * intakeStrokes;
// C. Calculate Actual Air Mass Flow (kg/s)
var massAirFlow_kgs = volFlow_m3s_theoretical * density * (VE_percent / 100);
// D. Calculate Fuel Mass Flow (kg/s)
var massFuelFlow_kgs = massAirFlow_kgs / AFR_val;
// E. Total Exhaust Mass Flow (kg/s)
var totalExhaust_kgs = massAirFlow_kgs + massFuelFlow_kgs;
// 4. Unit Conversions for Display
// Convert kg/s to kg/h
var massAir_kgh = massAirFlow_kgs * 3600;
var massFuel_kgh = massFuelFlow_kgs * 3600;
var totalExhaust_kgh = totalExhaust_kgs * 3600;
// Convert total to lb/min (1 kg/s = 132.277 lb/min)
var totalExhaust_lbmin = totalExhaust_kgs * 132.277;
// 5. Update UI
document.getElementById('resDensity').innerHTML = density.toFixed(3) + " kg/m³";
document.getElementById('resAirFlow').innerHTML = massAir_kgh.toFixed(1) + " kg/h";
document.getElementById('resFuelFlow').innerHTML = massFuel_kgh.toFixed(1) + " kg/h";
document.getElementById('resExhaustFlowKg').innerHTML = totalExhaust_kgh.toFixed(1) + " kg/h";
document.getElementById('resExhaustFlowLb').innerHTML = "(" + totalExhaust_lbmin.toFixed(2) + " lb/min)";
// Show results div
document.getElementById('resultsArea').style.display = "block";
}
Engine Exhaust Mass Flow Calculator
NA: 85-100%, Turbo: 90-110%+
1.0 = Atmospheric, >1.0 = Boosted
Stoichiometric gas is ~14.7
4-Stroke (Standard Car)
2-Stroke
Calculation Results
Intake Air Density:
0.00 kg/m³
Intake Air Mass Flow:
0.00 kg/h
Fuel Mass Flow:
0.00 kg/h
Total Exhaust Mass Flow:
0.00 kg/h
(0.00 lb/min)
Understanding Exhaust Mass Flow Rate
The Exhaust Mass Flow Rate is a critical parameter in automotive engineering and thermodynamics. It represents the total mass of exhaust gas expelled by an internal combustion engine over a specific period. Accurately calculating this figure is essential for sizing turbochargers, designing exhaust piping systems to minimize backpressure, and selecting appropriate catalytic converters.
Unlike simple volume flow, mass flow accounts for the density of the gas, which varies significantly with temperature and pressure. The most accurate way to estimate exhaust flow without expensive physical flow meters is by summing the mass of the air entering the engine and the mass of the fuel added to it.
The Calculation Formula
This calculator uses the "Intake Mass + Fuel Mass" method, which relies on the principle of conservation of mass. The logic follows these steps:
- 1. Calculate Air Density ($\rho$): Based on the Ideal Gas Law using the intake manifold temperature and absolute pressure.
Formula: $\rho = P / (R_{specific} \times T)$ - 2. Calculate Volumetric Flow ($\dot{V}$): Based on engine displacement, RPM, and the engine cycle (4-stroke vs 2-stroke).
- 3. Determine Air Mass Flow ($\dot{m}_{air}$): Multiply the volumetric flow by air density and the Volumetric Efficiency (VE).
- 4. Add Fuel Mass ($\dot{m}_{fuel}$): Calculated by dividing the air mass flow by the Air-Fuel Ratio (AFR).
- 5. Total Exhaust Flow: $\dot{m}_{exhaust} = \dot{m}_{air} + \dot{m}_{fuel}$
Input Parameters Explained
- Engine Displacement: The total swept volume of the engine (e.g., 2.0 Liters).
- Volumetric Efficiency (VE): A percentage representing how effectively the cylinder fills with air compared to its static volume. Naturally aspirated engines usually range from 85-100%, while forced induction (turbo/supercharged) engines can exceed 100%.
- Manifold Absolute Pressure (MAP): The air pressure in the intake manifold. Standard atmospheric pressure is ~1.0 Bar. If you are running 1.0 Bar of boost, your MAP is 2.0 Bar.
- Air-Fuel Ratio (AFR): The mass ratio of air to fuel. For gasoline engines, the stoichiometric ratio is 14.7:1. Richer mixtures (lower numbers, e.g., 12.5) are often used under high load.
Example Calculation
Consider a 2.0 Liter 4-stroke turbo engine running at 6,000 RPM. The boost pressure is set such that the absolute manifold pressure is 2.0 Bar, the intake temperature is 40°C, and the VE is 95%.
At these settings, the engine ingests approximately 760 kg/h of air. If running an AFR of 12.0 (rich for turbo), the fuel flow is roughly 63 kg/h. The total exhaust mass flow rate would be approximately 823 kg/h (or about 30 lb/min), which helps in selecting the correct turbine housing for the turbocharger.