| Fig. 1: EGR system — carbureted vehicle
without a computer controlled engine
|
| Fig. 2: EGR system — fuel injected vehicle
with a computer controlled engine
|
| Fig. 3: Cutaway view of an EGR thermo-vacuum valve assembly
|
| Fig. 4: Cutaway view of an EGR solenoid valve — carbureted
and SPFI engines
|
The function of the Exhaust Gas Recirculation (EGR) system is the reduction of NOx (oxides of nitrogen) by reducing the combustion temperature through recirculating a part of the exhaust gas into the cylinders.
The EGR valve opens in response engine vacuum. A thermo-valve, or on computer controlled engines a solenoid valve, is used to control the amount of vacuum reaching the EGR valve. When engine performance would suffer due to the recirculating gasses, normally during start-up, the valves remained closed to not allow vacuum to reach the EGR valve. When predetermined conditions are met, the valves open to allow the EGR valve to function according engine vacuum.
