Low Pressure Exhaust Gas Recirculation (ND EGR)

Low Pressure Exhaust Gas Recirculation (ND EGR)

Low pressure exhaust gas recirculation (ND EGR)
As of 09/2008, a second stage of exhaust gas recirculation will be introduced for the first time in BMW diesel vehicles, contributing to a reduction in nitrogen oxide (NOx) emissions. Nitrogen oxides arise in every engine during internal combustion. This additional system makes it possible to comply with stricter emission limits.

Components of the exhaust system in the US diesel:







Function principle in the US diesel:
After the diesel particle filter, a proportion of the exhaust gas is fed back through the low pressure EGR cooler into the intake tract. The inlet point is downstream of the mass air flow meter and is located before the large compressor. Withdrawal of the exhaust gas and subsequent feeding into the intake tract is activated by the DDE and is carried out with the help of a separate electropneumatically operated valve. The vacuum supply of this valve actuator is linked to the conventional vacuum system.
The exhaust gas fed back in this way lowers the combustion temperatures and oxygen content of the mixture in the cylinder. This reduces the NOx emissions in general.







Diagnosis instructions:
Direct activation of the ND EGR valve is available as a diagnostic procedure. An exact visual check of the adjustment of the valve is only possible after the components have been uncovered. The temperatures before the ND EGR cooler (the temperature before the SCR system) and after the ND AGR cooler can be read out in the diagnosis. All components are fitted close to the engine. If the actuator, valve or temperature sensor fail, the corresponding fault code memory entries are entered in the DDE.