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Home >> Peugeot >> 1984 >> 505 L4-2304cc 2.3L DSL XD-2 >> Repair and Diagnosis >> Powertrain Management >> Emission Control Systems >> Exhaust Gas Recirculation >> Description and Operation >> Turbocharged

Turbocharged

Fig. 9 Exhaust gas recirculation (EGR) system.:





The EGR system reduces oxides of Nitrogen (NOx) emissions by recirculating a portion of the exhaust gasses back into the engine. A vacuum controlled (EGR) valve is used to regulate recirculation of exhaust gasses into the intake stream.


The system used on turbocharged engines consists of a speed sensor, coolant temperature thermo switch, vacuum converter, electronic control module, single diaphragm EGR valve, vacuum damper, pre-filter and a non-return valve, Fig. 9. The ECM monitors engine RPM and coolant temperature, and controls vacuum signals applied to the EGR valve through a vacuum switching electro valve. the vacuum converter is operated by the injection pump lever and regulates the strength of the vacuum signal applied to the EGR valve, providing strong vacuum under light load conditions and progressively weaker vacuum as engine load (pump lever angle) increases.

When coolant temperature is below 118 degrees F, the switching valve is de-energized, no vacuum is applied to the EGR valve, and there is no recirculation. When coolant temperature is above 118 degrees F and engine speed is 1300-3100 RPM for automatic transmission models 1500-3100 RPM for manual transmission models, the electro valve is energized by the ECM and vacuum is transmitted to the EGR valve. When engine speed exceeds 3100 RPM, the ECM de-energies the switching valve to stop recirculation.

The vacuum converter is operated by the injection pump output lever through a link rod and regulates the vacuum signal applied to the EGR valve. Vacuum pump output is applied to the converter, and the vacuum signal applied to the EGR valve is progressively reduced as engine load increases. The EGR valve meters the amount of exhaust gas to be recirculated and the quantity of recirculated exhaust gas is directly proportional to the amount of vacuum applied to the valve. This provides maximum recirculation under light load operating conditions, with recirculation progressively reduced as engine load increases.


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