Samurai 2WD L4-1324cc 1.3L SOHC 5 Carb 8V (1987)
EGR Backpressure Transducer: Description and Operation
Fig. 5 EGR system schematic
The EGR system recirculates exhaust gas into the combustion chambers to reduce the formation of NOx. The operation of the EGR valve is controlled
by the EGR modulator which modulates the amount of vacuum applied to the EGR valve according to exhaust back pressure. Under low load conditions,
exhaust back pressure is low, Fig. 5, allowing air to enter vacuum passage which reduces the vacuum applied to the EGR valve resulting in less EGR
flow. Under higher load conditions, exhaust back pressure is high, causing full vacuum to be applied to the EGR valve resulting in maximum EGR flow.
At maximum load conditions, (full throttle) manifold vacuum is low, resulting in minimal EGR flow.
EGR operation is also controlled by coolant temperature. When coolant temperature is low, the Bi-metal Vacuum Switching Valve (BVSV) on the
intake manifold opens the EGR valve vacuum passage to the atmosphere, causing the valve to remain closed. Once normal operating temperatures are
reached, the BVSV closes and the EGR valve operates according to the EGR modulator.
