In internal combustion engines, exhaust gas recirculation (EGR) is a nitrogen oxide (NOx) emissions reduction technique used in petrol/gasoline and diesel engines. EGR works by recirculating a portion of an engine's exhaust gas back to the engine cylinders.
History
According to Construction Equipment, in 2002 five engine manufacturers began using cooled EGRs. Cummins, International, Mack, Detroit Diesel and Volvo have different engine designs, but all EGR systems can reduce the temperature of the exhaust by as much as 800 degrees.
Reduced Emissions
The reduction in temperature of the exhaust results in decreased formation of nitrogen oxides. This is accomplished by the diversion of between five and 30 percent of the exhaust through a cooler and back through the combustion chambers. There, the cooled gases lower the peak engine temperatures.
Maintenance
Construction Equipment indicates that cooled EGR system include sensors and actuators that are monitored electronically. Malfunctions in the system appear in the diagnostic log as fault codes. Typically these systems are maintenance-free as long as the related systems are operating properly.