Exhaust Gas Recirculation: Description and Operation

Purpose
The exhaust gas recirculation (EGR) system is a subsonic, closed loop Differential pressure feedback (DPFE) EGR system.

It is designed to:

^ reintroduce exhaust gas into the combustion cycle.

^ lower combustion temperatures.

^ reduce the formation of Oxides of Nitrogen (NOx).

Operation
The differential pressure feedback EGR system:

^ monitors EGR flow rate by the pressure drop across the metering orifice.

^ uses an EGR backpressure transducer as the feedback device.

^ controlled pressure is varied by the valve movement using vacuum output of the EGR vacuum regulator solenoid.

^ uses the EGR valve only as a pressure regulator rather than as a flow metering device.

^ allows for a more accurate assessment of EGR flow requirements.

Controls
The amount of exhaust gas reintroduced and the timing of the cycle are controlled by:

^ engine rpm.

^ engine vacuum.

^ exhaust system back pressure.

^ engine coolant temperature.

^ throttle position.