EGR System - Gasoline: Operation
When engine is not at operating temperature, no exhaust gas recirculation will occur since the switching valve is closed. Once engine temperature increases, the switching valve opens and exhaust gas recirculation is then controlled by other components of the system.
Vacuum modulator reacts to relieve exhaust backpressure, and to balance atmospheric pressure and vacuum to allow or stop EGR. The EGR cooler, used on Cressida, Land Cruiser and Supra, assists in reducing exhaust gas temperature before it is cycled into combustion chamber. This helps further reduce high temperatures that cause NOx formation.