What is the primary role of an exhaust-gas-recirculation system?

The primary role of an exhaust-gas-recirculation (EGR) system is to reduce emissions of nitrogen oxides (NOx). This is achieved by recirculating a portion of the engine's exhaust gases back into the combustion chamber. When these exhaust gases mix with the intake air, they lower the combustion temperature. Since NOx emissions are formed at high temperatures, reducing the temperature helps to minimize the formation of these harmful pollutants.

This function is critical in meeting environmental regulations and standards aimed at reducing air pollution. The EGR system is particularly important in modern vehicles that are designed to comply with stringent emissions guidelines, making it a vital component in promoting cleaner exhaust without a significant increase in fuel consumption or loss of engine performance.