Circuit Description

A properly operational EGR system will directly affect air/fuel requirements of the engine. Since exhaust gas being introduced in air/fuel mixture is an inert gas, less fuel is required to maintain a correct air/fuel ratio. Introducing exhaust gas into combustion chamber lowers combustion temperatures and reduces formation of NOX in the exhaust gas. Lower combustion temperature also prevent detonation. If EGR pintle were to remain closed, eliminating EGR, air/fuel mixture would be leaner. PCM would compensate for the lean condition by adding fuel, resulting in higher long term fuel trim values.