Tracker 4x4 L4-1590cc 1.6L (1993)
Exhaust Gas Recycle (EGR) Modulator: Description and Operation
The diaphragm mounted in the EGR modulator is operated by backpressure of the exhaust gas to open and close the valve. By this opening and closing
action of the valve, the EGR modulator controls the vacuum transmitted to the EGR valve. Under a low load condition such as low speed driving, the
exhaust pressure is low. In this state, the diaphragm in the EGR modulator is pushed down by the spring force and the modulator valve opens to allow air
into the vacuum passage from the outside. As a result, the vacuum transmitted to the EGR valve becomes smaller and so does the opening of the EGR
valve. Thus, less amount of exhaust gas is recirculated to the intake manifold.
Under a high load condition such as high speed driving, the exhaust pressure is high. By the high exhaust pressure, the diaphragm in the modulator is
pushed up and closes the valve. As the air does not enter the vacuum passage in this state, the vacuum transmitted to the EGR valve grows larger and so
does the opening of the EGR valve. Thus, larger amounts of exhaust gas is recirculated to the intake manifold.
