Carbureted Engine

The Exhaust Gas Recirculation (EGR) System is designed to reduce Oxides of Nitrogen emissions (NOx), by recirculating exhaust gas through the EGR valve and the intake manifold into the combustion chambers. It is composed of an EGR valve, EGR control valves A and B, EGR control solenoid valve A, thermosensor, and vacuum switch C.

The EGR valve is operated by vacuum from the carburetor port and provides EGR volume proportional to engine loads (intake air volume) by the operation of the EGR control valves A and B.

The EGR system recirculates exhaust gas only after the engine is up to normal operating temperature and then only while accelerating or crusing; these two conditions create the majority of NOx emissions. EGR flow Is cut off during idle, deceleration, and cold engine operation to assure good combustion during these conditions.
^ The vacuum signal is ported above the idle throttle valve position to eliminate EGR at idle.

The control unit senses the engine coolant temperature and intake manifold vacuum, and EGR flow is cut off by the EGR control solenoid valve A from the signal of control unit.

When engine coolant temperature is cold, EGR flow is cut off in order to maintain driveability, and when the engine coolant temperature is hot, EGR flow is cut off during deceleration or idling.