EGR System: Operation

When engine is below operating temperature, no exhaust gas recirculation is obtained. Increase in engine temperature allows control valves to regulate vacuum to EGR valve for gas recirculation.

Vacuum modulator is used to regulate exhaust backpressure, balance atmospheric pressure and vacuum to allow EGR operation at heavy throttle. The EGR cooler, used on the Cressida and Supra assists in reducing exhaust gas temperature before entering combustion chamber.