Exhaust Gas Recirculation: Description and Operation

EGR System Operations:

EGR System Operations Chart:

SYSTEM DESCRIPTION

This system is used to dilute the incoming air/fuel mixture with recirculated exhaust gases. Dilution of the incoming mixture lowers the peak flame temperature in the combustion chamber and thus, limits the formation of nitrous oxides (NOx).

EGR VALVE

This is a vacuum operated valve which opens and closes a passage from the exhaust manifold to the intake manifold. This allows flame temperature in the combustion chamber to be lowered by diluting the incoming mixture with exhaust gases. The EGR valve is controlled by the vacuum modulator.

VACUUM MODULATOR

This valve controls the amount of exhaust gases that are allowed into the intake manifold by sensing load conditions. The vacuum modulator is controlled by the vacuum switching valve.

VACUUM SWITCHING VALVE

This valve is controlled by the electronic control unit (ECU) which monitors the engine temperature and controls the conditions when the EGR system operates.