EGR Valve: Description and Operation

Typical EGR Valve:

PURPOSE
To reintroduce exhaust gases into the combustion cycle causing lower combustion chamber temperatures, thereby reducing the formation of nitrous oxide.

OPERATION
In the differential pressure feedback system, The Exhaust Gas Recirculation (EGR) valve is used only as a pressure regulator to increase or decrease the flow of exhaust gases across the metering orifice. Exhaust gases flowing through the orifice create a pressure drop that is converted into an electrical output signal sent to the Powertrain Control Module (PCM).

By regulating the EGR valve and monitoring the pressure drop created by exhaust gas flow through the metering orifice, the PCM has a more accurate assessment of EGR flow rate and requirements.