Exhaust Gas Recirculation: Description and Operation

Emission Control System Schematic:

DESIGN AND LOCATION
A single stage EGR valve (89) is bolted to the exhaust manifold of cylinders 4 - 6. The HFM-SFI control unit (N3/4) controls the introduction of exhaust gases via the EGR switchover valve (Y27).

EGR Valve (89):

OPERATION
The switch-over valve is activated (by the HFM-SFI control unit) at coolant temperatures above 48 °C (118 °F) and only if the engine is between the idle and full load condition. When the valve opens, intake manifold vacuum reaches the EGR valve and opens it. Some exhaust gases now flow from the exhaust manifold back into the intake manifold.