EGR Valve: Description and Operation

Exhaust Gas Recirculation Valve:

PURPOSE
The Exhaust Gas Recirculation (EGR) valve is designed to reintroduce exhaust gas into the combustion cycle lowering combustion temperatures and reducing the formation of Oxides of Nitrogen (Nox).

OPERATION

Vacuum Control
As vacuum applied to the EGR valve diaphragm overcomes the spring force, the valve begins to open. As the vacuum signal weakens, at 1.6 in (41 mm) Hg or less, the spring force closes the valve. The EGR valve is fully open at about 4.5 in (114 mm) Hg.

EGR Flowrate:

Exhaust Gas Flow
The amount of exhaust gas reintroduced and the timing of the cycle varies by calibration and is controlled by factors such as engine speed, engine vacuum, exhaust system back pressure, coolant temperature and throttle angle. All EGR valves are vacuum actuated. The vacuum diagram is on the emission decal for each calibration.