EGR Valve: Description and Operation

EGR Valve And EGR Control Valve:

PURPOSE
The Exhaust Gas Recirculation (EGR) valve routes exhaust gases from the exhaust manifold to the intake manifold during specified engine operating conditions.

OPERATION
When the EGR valve is opened (by back pressure modulated manifold vacuum), exhaust gasses are allowed to flow into the intake manifold. The exhaust gas then combines with the air/fuel mixture in the combustion chamber. Since there is less air/fuel mixture to burn in the combustion chamber during EGR operation, the temperature is reduced enough to limit formation of Oxides of nitrogen (NOx). If too much exhaust gas enters, combustion will not occur. Because of this, very little exhaust gas is allowed to pass through the valve, especially at low engine speeds.