EXHAUST GAS RECIRCULATION SYSTEM [SKYACTIV-D 1.8]

id0116q9159300


Exhaust Gas Recirculation System


Purpose, outline

•  The catalytic converter recirculates the exhaust gas in the combustion chamber and lowers the combustion temperature. By recirculating the exhaust gas, the NOx generated largely when the combustion temperature is high is reduced.
•  The HP-EGR system*1 and LP-EGR system*2 are used concurrently to perform optimum control according to the engine operation conditions.
*1  :The HP-EGR system circulates/recirculates exhaust gas in the intake manifold prior to it passing the turbine of the variable geometry turbocharger. Because the exhaust gas is recirculated immediately, responsiveness to the necessity of nitrous oxide concentration adjustment and the temperature increasing ability during engine warm-up are excellent.
*2  :The LP-EGR system sends/recirculates exhaust gas to the variable geometry turbocharger inlet after it passes the variable geometry turbocharger turbine. Because the intake air and exhaust gas are charged together, even high volumes in the charge region of the exhaust gas can be recirculated.


System diagram

ac3wzn00001044


Structure

•  The exhaust gas recirculation system consists of the following parts:

Part, system name

Reference
HP-EGR system
Intake shutter valve
(See Intake Shutter Valve.)
HP-EGR control valve
(See HP-EGR Control Valve.)
LP-EGR system
Exhaust shutter valve
(See Exhaust Shutter Valve.)
LP-EGR control valve
(See LP-EGR Control Valve.)
EGR cooler
―


Operation

•  The exhaust gas recirculation system operates the HP-EGR and LP-EGR systems according to the engine load.
am2zzn00003321
Ignition switched off (IG-OFF)
•  The open/closed condition of each valve when the ignition is switched off is as follows.
HP-EGR system
―  HP-EGR control valve: Fully closed
―  Intake shutter valve: Fully open
LP-EGR system
―  LP-EGR control valve: Fully closed
―  Exhaust shutter valve: Fully open
ac3wzn00001045
Light engine load
•  During light engine loads (except during diesel particulate filter regeneration), exhaust gas is recirculated by the HP-EGR system according to the request flow amount from the PCM to promote engine warming and assure responsiveness.
•  The open/closed condition of each valve during light engine loads is as follows.
HP-EGR system
―  HP-EGR control valve: Open (duty control)
―  Intake shutter valve: Closed (duty control)
LP-EGR system
―  LP-EGR control valve: Fully closed
―  Exhaust shutter valve: Fully open
ac3wzn00001046
Medium engine load
•   During medium engine loads (except during diesel particulate filter regeneration), exhaust gas is recirculated by both the LP-EGR and HP-EGR systems according to the request flow amount from the PCM.
•  The open/closed condition of each valve during medium engine loads is as follows.
HP-EGR system
―  HP-EGR control valve: Open (duty control)
―  Intake shutter valve: Open (duty control)
LP-EGR system
―  LP-EGR control valve: Open (duty control)
―  Exhaust shutter valve: Closed (duty control)
ac3wzn00001047
High engine load
•  During high engine loads (except during diesel particulate filter regeneration), the exhaust gas is recirculated by the LP-EGR system according to the request flow amount from the PCM to promote charging.
•  The open/closed condition of each valve during high engine loads is as follows.
HP-EGR system
―  HP-EGR control valve: Fully closed
―  Intake shutter valve: Fully open
LP-EGR system
―  LP-EGR control valve: Open (duty control)
―  Exhaust shutter valve: Open (duty control)
ac3wzn00001048
During diesel particulate filter regeneration
•  During diesel particulate filter regeneration, exhaust gas is recirculated by both the LP-EGR systems according to the request flow amount from the PCM.
•  The open/closed condition of each valve during diesel particulate filter regeneration is as follows.
HP-EGR system
―  HP-EGR control valve: Fully closed (constantly)
―  Intake shutter valve: Open (duty control) (during light engine load/medium engine load)*1
LP-EGR system
―  LP-EGR control valve: Open (duty control) (during light engine load/medium engine load)*2
―  Exhaust shutter valve: Fully open (constantly)
*1  :During high engine loads, the intake shutter valve is fully open due to the large amount of air volume required.
*2  :Because the exhaust gas temperature is high during compulsory diesel particulate filter regeneration or under high engine load conditions, the LP-EGR control valve is fully closed to prevent combustion difficulties caused by the exhaust gas being recirculated.
ac3wzn00001049
•  For details on the exhaust gas recirculation system, refer to the CONTROL SYSTEM. (See EGR CONTROL [SKYACTIV-D 1.8].) (See INTAKE SHUTTER VALVE CONTROL [SKYACTIV-D 1.8].) (See EXHAUST SHUTTER VALVE CONTROL [SKYACTIV-D 1.8].)


Intake Shutter Valve


Purpose, function

•  The intake shutter valve facilitates recirculation induction of the exhaust gas by adjusting the intake air volume and channeling the airflow to the intake manifold side.
•  The intake air amount to the engine is reduced to increase the exhaust gas temperature easily while the DPF is carrying out combustion. Due to this, the particulate matter (PM) collected in the DPF is burned and eliminated.
•  The valve is closed to cut the intake air when the engine switch is off to reduce the shock when the engine is turned off.


Construction

•  The intake shutter valve is located on intake manifold.
atsuzn00000038
•  The intake shutter valve consists of the shutter valve, valve shaft, valve, spring, valve gear, mid gear, DC motor, and pinion.
am2zzn00003334
•  The intake shutter valve has an integrated intake shutter valve position sensor. For details on the intake shutter valve position sensor, refer to the CONTROL SYSTEM. (See INTAKE SHUTTER VALVE POSITION SENSOR [SKYACTIV-D 1.8].)


Operation

•  The intake shutter valve is opened to the valve opening angle according to the energization current flowing to the DC motor from the PCM.
am2zzn00003335
•  The intake shutter valve performs coordinated control with the LP-EGR control valve, HP-EGR control valve, and exhaust shutter valve. For details on the exhaust shutter valve, refer to the CONTROL SYSTEM. (See INTAKE SHUTTER VALVE CONTROL [SKYACTIV-D 1.8].)
•  If the shutter valve has a malfunction and the DC motor control is disabled, the shutter valve is opened to the fully open position by the return spring. As a result, the air amount necessary to keep the vehicle moving is assured.


HP-EGR Control Valve


Purpose, function

•  The HP-EGR control valve adjusts the exhaust gas volume recirculated to the combustion chamber according to the engine operation conditions to reduce the NOx generated largely when the combustion temperature in the combustion chamber is high.


Construction

•  The HP-EGR control valve is located at the front of the engine compartment.
atsuzn00000039
•  The HP-EGR control valve consists of the DC motor, valve, spring, valve gear, and mid gear.
ac3wzn00001050
•  The HP-EGR control valve has an integrated HP-EGR control valve position sensor. For details on the HP-EGR control valve position sensor, refer to the CONTROL SYSTEM. (See HP-EGR CONTROL VALVE POSITION SENSOR [SKYACTIV-D 1.8].)


Operation

•  The HP-EGR control valve is opened to the valve opening angle according to the energization current flowing to the DC motor from the PCM.
am2zzn00003314
•  The HP-EGR control valve performs coordinated control with the intake shutter valve, LP-EGR control valve, and exhaust shutter valve. For details on the HP-EGR control valve control, refer to the CONTROL SYSTEM. (See EGR CONTROL [SKYACTIV-D 1.8].)
•  In the event that HP-EGR control valve has a malfunction and the DC motor control is disabled, the shutter valve is closed to the fully closed position by the return spring. As a result, the air volume necessary to keep the vehicle moving is assured.


Exhaust Shutter Valve


Purpose, function

•  The exhaust shutter valve adjusts the exhaust gas volume recirculated to the EGR cooler side to adjust the exhaust gas volume released to the atmosphere.


Construction

•  The exhaust shutter valve is located in the exhaust pipe.
atsuzn00000214
•  The exhaust shutter valve consists of the exhaust shutter valve position sensor, valve gear, mid gear, pinion, DC motor, spring, valve shaft, and valve.
ac3wzn00001037
•  The exhaust shutter valve has an integrated exhaust shutter valve position sensor. For details on the exhaust shutter valve position sensor, refer to the CONTROL SYSTEM. (See EXHAUST SHUTTER VALVE POSITION SENSOR [SKYACTIV-D 1.8].)


Operation

•  The exhaust shutter valve is opened to the valve opening angle according to the energization current flowing to the DC motor from the PCM.
am2zzn00003338
•  The exhaust shutter valve performs coordinated control with the intake shutter valve, LP-EGR control valve, and HP-EGR control valve. For details on the exhaust shutter valve control, refer to the CONTROL SYSTEM. (See EXHAUST SHUTTER VALVE CONTROL [SKYACTIV-D 1.8].)
•  In the event that the exhaust shutter valve has a malfunction and the DC motor control is disabled, the shutter valve is opened to the fully open position by the return spring. Due to this, the air amount necessary to keep the vehicle moving is assured.


LP-EGR Control Valve


Purpose, function

•  The LP-EGR control valve adjusts the exhaust gas volume recirculated to the variable geometry turbocharger according to the engine operation conditions to reduce the NOx generated largely when the combustion temperature in the combustion chamber is high.


Construction

•  The LP-EGR control valve is located at the rear of the engine compartment.
atsuzn00000040
•  The LP-EGR control valve consists of the DC motor, mid gear, valve gear, spring, valve shaft, and the valve.
am2zzn00003310
•  LP-EGR control valve has an integrated LP-EGR control valve position sensor. For details on the LP-EGR control valve position sensor, refer to the CONTROL SYSTEM. (See LP-EGR CONTROL VALVE POSITION SENSOR [SKYACTIV-D 1.8].)


Operation

•  The LP-EGR control valve is opened to the valve opening angle according to the energization current flowing to the DC motor from the PCM.
am2zzn00003311
•  The LP-EGR control valve performs coordinated control with the intake shutter valve, HP-EGR control valve, and exhaust shutter valve. For details on the LP-EGR control valve control, refer to the CONTROL SYSTEM. (See EGR CONTROL [SKYACTIV-D 1.8].)
•  In the event that the LP-EGR control valve has a malfunction and the DC motor control is disabled, the shutter valve is closed to the fully closed position by the return spring. As a result, the air amount necessary to move the vehicle is assured.