EXHAUST GAS RECIRCULATION (EGR) SYSTEM <4HN>




System Configuration Diagram








EGR VALVE (DC MOTOR)



The EGR valve is mounted at the exhaust manifold side of cylinder head. The EGR valve has the integrated motor that changes the opening degree of the exhaust gas induction valve to control the amount of the exhaust gas recirculation.
The engine-ECU controls the EGR valve by changing the electrical currents going through the motor coil.

EGR VALVE POSITION SENSOR



The EGR valve position sensor is installed in the EGR valve.
EGR valve position sensor outputs voltage to engine-ECU based on the EGR valve opening angle.
Engine-ECU uses this signal to detect degree of the EGR valve opening.

EGR COOLER SOLENOID VALVE



The EGR cooler solenoid valve which is mounted at the inlet manifold side of cylinder head via the bracket is an ON/OFF control type solenoid valve.
The engine-ECU actuates this solenoid valve to open and close the EGR cooler by-pass valve which allows the EGR to flow or not to flow through the EGR cooler.

Cold State of Engine



When the engine coolant is at low temperatures, the EGR cooler solenoid valve is in the ON position. The EGR cooler by-pass valve closes the passage at the EGR cooler side and opens the by-pass passage in order that the exhaust gas cannot flow through the EGR cooler.
In this way, the catalytic converter and the engine reach their operating temperatures within the short space of time. The hydrocarbon, carbon monoxide and particulate emissions are reduced as a result.

Hot State of Engine



When the engine coolant is higher than the specified temperatures, the EGR cooler solenoid valve is in the OFF position. The EGR cooler by-pass valve opens the passage at the EGR cooler side and closes the by-pass passage in order that the exhaust gas can flow through the EGR cooler.
The recirculated exhaust gas now flows through the EGR cooler. This helps to further reduce NOx.