Exhaust Gas Recirculation (Egr) System - Mitsubishi Eclipse Technical Information Manual

ENGINE <NON-TURBO> - Emission Control System

EXHAUST GAS RECIRCULATION (EGR) SYSTEM

The exhaust gas recirculation (EGR) system lowers
the nitrogen oxide (NOx) emission level. When the
air/fuel mixture combustion temperature is high, a
large quantity of nitrogen oxides (NOx) is generated
in the combustion chamber. Therefore, this system
recirculates part of emission gas from the exhaust
port of the cylinder head to the combustion chamber
through the intake manifold to decrease the air/fuel
mixture combustion temperature, resulting in reduc-
tion of NOx.
OPERATION
The electronic EGR transducer (EET) contains an
electrically operated solenoid and a back-pressure
transducer. The PCM operates the solenoid. The
PCM determines when to energize the solenoid.
Exhaust system back-pressure controls the trans-
ducer.
When the PCM energizes the solenoid, vacuum
does not reach the transducer. Vacuum flows to
the transducer when the PCM energizes the sole-
noid. When exhaust system back-pressure becomes
high enough, it fully closes bleed valve in the trans-
The EGR flow rate is controlled by the EGR valve
so as not to decrease the driveability.
The EGR system contents:
EGR tube
l
EGR valve
l
Electronic EGR transducer (EET)
l
Connecting hoses
l
back-pressure closes the transducer bleed valve,
vacuum flows through the transducer to operate
the EGR valve.
Energizing the solenoid, but not fully closing the
transducer bleed hole (because of low back-pres-
sure), varies the strength of vacuum applied to the
EGR valve. Varying the strength of the vacuum
changes the amount of EGR supplied to the engine.
This provides the correct amount of exhaust gas
recirculation for different operating conditions.