Description - Operation

OPERATION





Figure 1 EGR COOLER

The Exhaust Gas Recirculation (EGR) lowers the cylinder temperatures by introducing combustion gasses into the air fuel mixture in the cylinder. The reduction of the cylinder temperature reduces the NOx emissions. This system uses a throttle valve (1) and EGR cooler (2).






Figure 2 EGR COOLER COMPONENTS

When the ECM indicates that EGR is required, vacuum is supplied to the EGR valve. Exhaust gasses travel from the cylinder to the EGR cooler. The EGR cooler is a water cooled heat exchanger designed to remove heat from the exhaust gasses. The exhaust gasses then travel from the EGR cooler, through the EGR tube, to the throttle body.






Figure 3 EGR TUBE - COOLER TO INTAKE

The throttle body is a valve that creates a venturi effect to help draw the exhaust gasses from the EGR tube and into the intake manifold. The throttle valve is normally open. Under normal EGR requirements, the throttle body valve is open.






Figure 4 EGR SYSTEM

When additional EGR is required, the ECM uses a pulse width signal to command the EGR solenoid (3) to allow vacuum from the vacuum pump to the throttle valve. The vacuum closes the throttle valve which causes the venturi to draw additional EGR into the cylinder.