Calif

DPFE EGR System Diagram, OBD II:

PURPOSE
To reintroduce exhaust gases into the combustion cycle, lowering combustion temperatures thus, reducing the formation of Nitrous Oxide (NOx).

OPERATION

Differential Pressure Feedback System.
The Powertrain Control Module (PCM) monitors the Exhaust Gas Recirculation (EGR) flow rate by the pressure drop across a metering orifice.The pressure drop across the orifice is converted into a signal by an EGR Backpressure Transducer which will vary depending on flow.

Determining the EGR Flow Rate
The PCM will use differential pressure feedback signal along with other inputs, such as engine rpm, engine vacuum, exhaust system back pressure, engine coolant temperature and throttle angle to determine the timing and volume of exhaust gases to be reintroduced into the combustion cycle.

EGR System And EGR Valve Control
The PCM will issue a duty cycle output command to the EGR Vacuum Regulator (EVR) Control Solenoid to regulate the vacuum signal to the EGR valve. The movement of the EGR valve pintle will vary the volume of exhaust gases flowing past the metering orifice, thus causing the pressure drop signal to the PCM to vary in the same proportion. This is a continuous closed-loop cycle.

Using the EGR valve as a "pressure regulator" rather than a flow metering device, allows for a more accurate assessment of EGR flow requirements.

CONSTRUCTION
Consists of PCM, EGR Backpressure Transducer, EGR valve, Metering Orifice, Upstream and Downstream Pressure Hose and EGR Vacuum Regulator Solenoid.