The Exhaust Gas Recirculation (EGR) system is a part of a vehicle’s exhaust and intake system, and its location is critical for proper functioning. Here’s a detailed explanation:
1. General Location
- The EGR valve is installed between the exhaust manifold and the intake manifold.
- It allows a controlled portion of exhaust gases to flow back into the intake manifold, mixing with fresh air.
Typical layout in a diesel/petrol engine:
Exhaust Manifold → EGR Valve → Intake Manifold → Cylinders
- Some modern diesel engines also include an EGR cooler (before the valve) to lower exhaust gas temperature before it enters the intake.
Also Read: How to replace EGR Valve?
2. Key Components Around the EGR
- EGR Valve
- Controls the amount of exhaust gas recirculated.
- Can be vacuum-operated (older vehicles) or electronically controlled (modern vehicles).
- EGR Cooler (Optional)
- Reduces exhaust gas temperature to prevent knocking and improve efficiency.
- Located between exhaust manifold and EGR valve.
- Sensors
- Temperature sensors: Before and after the EGR valve to monitor gas temperature.
- Differential pressure or flow sensors: Detect proper EGR operation.
3. Variations by Engine Type
| Engine Type | Typical EGR Location | Notes |
|---|---|---|
| Diesel Cars / Trucks | Between exhaust manifold and intake manifold, often with cooler | Ensures high NOₓ reduction and helps passive regeneration of DPF |
| Petrol Engines | Intake manifold side, connected to exhaust manifold | Simpler design; reduces NOₓ formation but less soot concerns |
| Turbocharged Diesel | After turbocharger (HP-EGR) or after DPF (LP-EGR) | HP-EGR: uses hot exhaust; LP-EGR: cleaner gas with less soot |
4. How to Identify EGR in Your Vehicle
- Look for a valve with a pipe connecting the exhaust to the intake manifold.
- Often made of metal or heat-resistant plastic, with wires or vacuum hoses attached for control.
- Larger in diesel engines, sometimes integrated with EGR cooler.
In Short
The EGR is located between the exhaust manifold and intake manifold, sometimes including a cooler.
It recirculates exhaust gases into the intake to lower combustion temperatures and reduce NOₓ emissions.
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