Exhaust Gas Recirculation: Description and Operation

EGR OPERATION

Exhaust gas recirculation is used to reduce oxides of nitrogen emissions in the vehicle exhaust. EGR uses partial recirculation of exhaust gases from a port in the cylinder head to a port in the intake manifold. The EGR valve controls the flow of exhaust gas in response to ported vacuum. At partial throttle settings ported vacuum is high and the EGR valve is open. At full throttle and idle port vacuum is low and the EGR valve remains closed.

Fig. 73 Complete Emission Control System Diagram (Federal Non-Turbo):

FEDERAL VEHICLES

Federal vehicles use a thermo valve to prevent EGR operation until the engine has reached operating temperature.

Fig. 74 Complete Emission Control System Diagram (California Non-Turbo):

CALIFORNIA VEHICLES