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Exhaust Gas Recirculation

Exhaust gas recirculation (EGR) means the controlled feeding of combustion gases back into the combustion chamber. Exhaust gas recirculation is an effective method of reducing the nitrogen oxide (NOx) levels at the combustion stage.
When the fuel/air mixture burns, the formation of nitrogen oxides increases at a disproportionately high rate as the temperature rises. Recirculating a portion of the exhaust gas back to the chamber lowers the combustion temperature inside the cylinder, reducing the rate of NOx formation. Emission behaviour can therefore be influenced as the engine load conditions change by the controlled addition of exhaust gas. The exhaust gas is directed back into the intake tract via a system of pipes with the aid of a valve, controlled electronically by the engine management unit; from there it is drawn back into the combustion chamber.