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Exhaust gas recirculation (EGR), 4-cyl

Exhaust gas recirculation (EGR), 4-cyl


For a diesel engine, which operates with excess air in combustion, there is currently no effective catalytic converter technology available for reducing NO x emissions. This means that the formation of NO x has to be restricted.

With an EGR-system (Exhaust Gas Recirculation), a controlled amount of exhaust emissions are directed to the induction side where they are mixed with the intake air. The result is slower combustion at a lower temperature and maximum pressure, which in turn hampers formation of NO x .

The EGR is electronically controlled and has its own processor. The EGR is governed by a PWM signal at 140 Hz from PSG 16.

Internally in the EGR valve, the processor keeps track of how much the valve is open. Thus, when PSG 16 indicates how much it should open or close, reaction time is very quick. This keeps combustion temperature low, which effectively prevents the formation of NO x . The EGR function is switched off after one minute of idling to prevent carbon deposits from forming.

Because it has its own processor, the EGR valve can perform self-diagnostics. For example, if it seizes or sticks, it informs the engine control module with a PWM signal of 100 Hz and a DTC is generated. If there is a DTC for EGR control, the engine will reduce torque and switch off the EGR and Swirl functions. The Check Engine lamp will also light.