Exhaust Gas Recirculation: Description and Operation

Fig. 5 Exhaust Gas Recirculation System:

The EGR system, Fig. 5, helps lower the peak burning temperatures and pressures within the combustion chambers, limiting the formation of oxides of nitrogen (NOx). This is accomplished by drawing a portion of the exhaust gases into the intake manifold under certain engine operating conditions. These gases mix with and dilute the incoming air/fuel mixture charge, which results in lower combustion chamber temperatures and pressures.