Exhaust Gas Recirculation: Description and Operation

EGR Valve:

SYSTEM OPERATION

The EGR system is an emission reducing system that concentrates primarily on the reduction of oxides of nitrogen (NOx). The purpose of the EGR system is accomplished by allowing a specified amount of hot exhaust gas to flow from the exhaust manifold into the intake manifold to mix with the incoming air/fuel mixture. This mixture enters the combustion chamber and lowers the peak flame temperature during combustion. This reduction in combustion temperature reduces the possibility of ignition knock and the level of NOx output.

This system is composed of the following components: EGR control valve, Back-Pressure transducer, and an electronically controlled solenoid.

EGR Control Valve and Electronic Transducer:

Electric EGR Transducer (EET):

CONTROL VALVE AND ELECTRONIC TRANSDUCER

This system has an electronically controlled vacuum solenoid that is an integral part of the Electronic EGR Transducer (EET). The SBEC II monitors engine coolant temperature and other operating conditions to determine when to energize the EGR solenoid. The electronic portion of the solenoid receives its electronic signal from the SBEC II. The solenoid uses this signal to regulate the amount of vacuum supplied to the EGR transducer. When the SBEC II supplies a ground to the solenoid (energizing), vacuum is cut off from the EGR transducer. When the SBEC II removes the ground from the solenoid (de-energizing), vacuum is allowed to flow through the solenoid and out to the EGR transducer. Vacuum is supplied to the EET by a ported vacuum signal from the throttle body. The transducer measures the amount of exhaust gas backpressure on the exhaust side of the EGR valve and it varies the amount of vacuum supplied to the EGR valve. The transducer uses this backpressure signal to supply the correct amount of vacuum to the EGR valve depending on engine load conditions.

NOTE: If the EGR solenoid electrical connector is disconnected, the EGR will operate continuously. This will result in poor engine performance and driveability under certain conditions.