Exhaust Gas RECIRCULATION (EGR) System: Description
The exhaust gas recirculation system (EGR) is designed to reintroduce small amounts of exhaust gas into the combustion cycle, thus reducing the amounts of NOx emissions. The amount of exhaust gas recycled and the timing of the cycle are controlled by such factors as engine vacuum, exhaust system backpressure and temperature.
Typical systems consist of an EGR valve, a spacer plate on which the valve is mounted (usually under the carburetor), a vacuum amplifier, a check valve, and a ported vacuum switch (PVS).