Exhaust gas recirculation (EGR) (Engine management system - EDC)

EXHAUST GAS RECIRCULATION (EGR)

During certain running conditions the EGR system directs exhaust gases into the intake manifold to be used in the combustion process. The principal effect of this is to reduce combustion temperatures, which in turn reduces Oxides of Nitrogen (NO_x) emissions.

The EGR diaphragm valve is vacuum operated through a solenoid valve, mounted on the right hand suspension turret. When the Engine Control Module (ECM) determines that exhaust gas recirculation should take place, the solenoid valve is modulated and vacuum, supplied by the brake servo vacuum pump, opens the EGR valve. Exhaust gases are then fed through a pipe into the exhaust manifold.

An air flow meter, mounted in the air intake pipe, senses the volume of air entering the engine. Using the principle that an increase in EGR will lead to a decrease in the intake air flow, the air flow meter is used by the ECM to monitor the amount of exhaust gases being recirculated. This feedback signal allows the ECM to accurately control the volume of exhaust gases being recirculated.