EGR System - Gasoline: Operation
Exhaust gases are directed from exhaust manifold, through EGR tube and into EGR control valves. The BPT or VVT valves monitor exhaust pressure in order to control intake manifold vacuum applied to EGR control valve. The EGR control valve regulates actual amount of exhaust gas to be recirculated into intake manifold.
Open/Close operation of EGR control valve is directed by the thermal vacuum valve which operates on ported vacuum and engine coolant termperature. EGR system does not operate at idle or under full throttle (heavy load) conditions, when coolant temperature is low (thermal vacuum valve closed), or when exhaust pressure is low.