EGR System: Description

The Exhaust Gas Recirculation (EGR) system used on General Motors vehicles is designed to reduce emission of Oxides of Nitrogen (NOx). This process is accomplished by lowering combustion temperatures of burning gases by recirculated metered amounts of exhaust gases into the intake manifold where they are mixed with the air/fuel mixture.

There are 2 types of EGR systems; ported and exhaust backpressure modulated. Ported system uses a timed vacuum port in the carburetor to regulate the amount of exhaust gas recirculation.

The backpressure modulated system regulates the timed vacuum according to the exhaust backpressure level. Several types of control sensors are used. These are described under OPERATION.