Chapter X Electronic Control EGR System
Great Wall Baoding Internal Combustion Engine
Manufacturing Company Limited
457
Chapter X Electronic Control EGR System
Section I General
The electronic control EGR technology is adopted in GW4D20/GW4D20B turbocharged diesel engine so
that its overall emission can reach National
Ⅳ
standard.
EGR system can be used to control the exhaust gas recirculation (EGR system) for modern engine.
Through introducing a small amount of the exhaust gas produced by the engine into the cylinder and
blending it with the fresh air, the exhaust gas recirculation system reduces the emission of the pollutant.
Through reducing the combustion rate to decrease the peak value of the combustion temperature, the
emission amount of Nox can be reduced.
The EGR rate should be adjusted precisely according to different working conditions of the engine in the
EGR system.
As the engine load changes, the exhaust gas amount introduced into the cylinder should also be
adjusted accordingly to always allow the EGR system to work under the condition of good emission
control and good engine power.
If the introduced exhaust gas is too much, the engine power will decrease, the smoke will increase and
the engine will produce louder noise. If the introduced exhaust gas is too little, the emission requirement
can not be met for the engine. Therefore, for each working condition (load, rotation speed and water
temperature) of the engine, there is always an optimal EGR rate (the ratio of the exhaust gas
recirculation mass to the fresh air mass).
The EGR system of the engine is equipped with the EGR cooler, whose function is to cool the exhaust
gas entering the cylinder to reduce the intake air temperature so as to reduce the Nox as well as the CO
and HC emission volumes.
When the EGR valve, the vacuum adjuster and the EGR cooler are damaged, timely replace them
according to the manufacturer’s requirement and the specification.
Fig. 10-1-1 Schematic diagram of the EGR electronic control system
EGR valve
Recirculated exhaust gas
EGR
condenser
Exhaust gas
Air intake
Vehicle speed
signal
Cooling water
temperature signal
Air flow sensor signal
Engine speed signal
Footboard signal
