EGR System - Gasoline: Description
The exhaust gas recirculation system is designed to control formation of NOx emissions. This is done by reintroducing some exhaust gas back into the combustion chamber. The exhaust gases are lower in temperature than the combustion flame. By reducing combustion chamber temperatures, NOx formation is reduced.
California vehicles use an EGR valve and thermal vacuum valve. See Fig 1 . The system on Federal vehicles includes an EGR valve, coolant switch, choke switch, gearbox switch, and an EGR vacuum solenoid. See Figure .