Exhaust Gas Recirculation: Description and Operation

Fig. 21 Exhaust Gas Recirculation System (Non-Supercharged):

Fig. 24 Exhaust Gas Recirculation System Operation (Non-Supercharged):

SYSTEM DESCRIPTION

The exhaust gas recirculation (EGR) system is used to dilute the incoming air/fuel mixture with recirculated exhaust gases. Dilution of the incoming mixture lowers the peak flame temperature limiting the formation of nitrous oxides (NOx).

BI-METAL VACUUM SWITCHING VALVE

The bi-metal vacuum swiching valve (BVSV) is a temperature sensitive valve that controls vacuum used to operate the EGR valve.

EGR VALVE

The vacuum operated EGR valve opens and closes a passage from the exhaust manifold to the intake manifold. Flame temperature in the combustion chamber is 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.

VACUUM SWITCHING VALVE

The ECU controlled vacuum switching valve determines when the EGR system is operated by controlling the vacuum flow to the system.