Exhaust Gas Recirculation: Description and Operation

EGR Operation:

The EGR system functions to reduce oxides of nitrogen (NOx) emissions. When the engine is under load, the EGR valve admits a small amount of exhaust gas into the air/fuel charge. The exhaust gas is essentially inert (contains no fuel or oxidizer) and reduces peak combustion temperatures and pressures by absorbing some of the heat of combustion without participating in the actual burn. Greater amounts of exhaust gas are metered in as engine speed and load are increased.