Exhaust Gas Recirculation (EGR) System Description: Notes

The EGR system is used to reduce the amount of nitrogen oxide (NOx) emission levels caused by high combustion temperatures. At temperatures above 1, 371°C (2, 500°F), oxygen and nitrogen combine to form NOx. Introducing small amounts of exhaust gas back into the combustion chamber displaces the amount of oxygen entering the engine. With less oxygen in the air/fuel mixture and as a result combustion temperatures are decreased, restricting the formation of NOx.

The EGR valve motor is a direct current (DC) motor utilizing a worm gear that extends from the motor to push on the EGR valve stem. The worm gear is not attached to the valve stem and can only force the valve open. A return spring is used to force the valve closed.