What is the function of the EGR (Exhaust Gas Recirculation) system?

The function of the EGR (Exhaust Gas Recirculation) system is primarily to lower the temperature in the combustion chambers, which directly contributes to reducing nitrogen oxide (NOx) emissions. By recirculating a portion of the exhaust gases back into the intake manifold, the EGR system dilutes the air-fuel mixture, effectively lowering the peak combustion temperatures. This is important because high combustion temperatures are a significant contributor to the formation of NOx pollutants, which are harmful to the environment and are regulated by emissions standards.

While increasing fuel efficiency is a desirable outcome, it is not the primary function of the EGR system. Similarly, while the EGR system does have effects on engine noise and may influence power generation indirectly, these are not its main purposes. The fundamental goal of the EGR system is to control emissions, particularly by managing combustion temperatures, which is accurately reflected in the choice that emphasizes lowering cylinder temperatures.