Exhaust gas recirculation (EGR) is a reliable and proven method for emission control that is today even more indispensable than ever.
Pierburg, the European market leader where exhaust gas recirculation is concerned, provide advice on components, causes of failure and remedies.
The first EGR systems were used on petrol engines at the beginning of the seventies. Around 1988, this technology also found its way into vehicles with diesel engines. Nowadays, practically all modern diesel engines are provided with EGR technology so as to be able to comply with present-day emission regulations. Right: Electrical EGR valve
At first sight, one may wonder how it is possible to reduce pollutants by means of exhaust gases in the intake air. By adding exhaust gas, however, the oxygen content in the fuel/air mixture is reduced and, as a result, the combustion temperature in the cylinders lowered.
To achieve this, exhaust gas recirculation is only connected at defined operating points: On petrol engines this is above idling speed up to the upper partial load, on diesel engines up to approx. 3,000 min-1 and mean load. No exhaust gas recirculation is made at full load, though.
In addition, exhaust gas recirculation reduces hydrocarbon, particulate and noise emissions on diesel cars, while on petrol-engine cars the CO2 emissions and the fuel consumption are lowered. This reduction of consumption in the case of petrol engines can be explained by the lower charge-exchange losses and improved mixture formation due to the heat supplied with the exhaust gas.