EMISSION CONTROL SYSTEM


  1. FUNCTION OF MAIN COMPONENTS


    1. The main components of the 1KR-FE emission control system are as follows.

      Component Function
      TWC The TWC reduces emissions by oxidation of CO and HC in exhaust gas and reduction of NOx.
      Oxygen Sensor This sensor detects the oxygen concentration in the exhaust emission by measuring the electromotive force which is generated in the sensor itself.
      EGR Valve Assembly Opens and closes based on signals from the ECM and controls the flow rate of the exhaust gas in the EGR bypass.
      PCV Valve (Ventilation Valve Sub-assembly) Opens and closes the valve using vacuum generated in the intake manifold and controls the flow rate of the blowby gas.
      Purge VSV (Duty Vacuum Switching Valve) Open and closes the valve based on signal from ECM and controls the flow rate of the evaporative emission.
      ECM

      • Controls the volume of fuel consumed based primarily on the signal from the oxygen sensor, with minor corrections based on the signal from the oxygen sensor. This control optimizes the air fuel ratio.

      • Regulates the EGR volume in accordance with the various sensor signals.

  2. SYSTEM CONTROL


    1. EGR Control


      1. This system is designed to reduce and control NOx formation due to a slight reduction of the peak temperature in the engine combustion chamber and to improve fuel economy, which is accomplished by introducing a small amount of inert gas into the intake passage.

      2. By sensing the engine driving conditions and actual amount of the EGR valve assembly opening, the ECM operates the EGR valve assembly and throttle control motor, and regulates the amount of exhaust gas.

      3. The EGR valve assembly regulates the flow volume of some exhaust gas passing through the cylinder head sub-assembly and returns the gas to the intake manifold.

        A01UWCQE02

    2. Blowby Gas Ventilation System


      1. By introducing blowby gas that has a large amount of HC into the air intake side and burning it again, the system attempts to enhance the emission performance. Returning blowby gas volume is regulated to the appropriate amount corresponding to the engine operating conditions, reducing the engine oil quantity taken away and engine idling speeds.

      2. The Positive Crankcase Ventilation (PCV) valve passage returns the blowby gas into the area after the throttle valve in accordance with the intake manifold vacuum.

      3. When load is low, the passage from the cylinder head cover sub-assembly to the area before the throttle valve increases the air purification performance inside the crankcase by introducing fresh air, and when load is high, the passage circulates the blowby gas together with the PCV Valve (ventilation valve sub-assembly) side passage due to the intake manifold vacuum.

      4. An oil separator chamber has been provided to reduce oil degradation and consumption.

        A01UW1QE02
        Text in Illustration
        *1 Air Cleaner Case *2 Intake Manifold
        *3 Cylinder Head Cover Sub-assembly *4 PCV Valve (Ventilation Valve Sub-assembly)
        *5 Oil Separator *6 Crank Case
        A01UWJU Blowby Gas A01UWQJ Fresh Air

  3. CONSTRUCTION


    1. Three-Way Catalytic converter (TWC)


      1. TWCs are provided in the exhaust manifold converter sub-assembly and also in the front exhaust pipe assembly.

      2. An exhaust manifold converter sub-assembly with an integrated TWC is used for warm-up of the TWC.

      3. This TWC enables to improve exhaust emissions.

        A01UVZEE02
        Text in Illustration
        *1 TWC - -

    2. EGR Valve Assembly


      1. A step motor is used on the EGR valve assembly to enable the ECM to directly control the EGR valve assembly.

      2. The engine coolant circulates through the EGR valve assembly to ensure proper cooling performance.

        A01UW84E02
        Text in Illustration
        *1 No. 1 Intake Manifold Insulator *2

        • EGR Valve Assembly


          • Step Motor
        *a Engine Coolant Out *b Engine Coolant In
        *c EGR Valve Assembly Cross Section - -
        A01UWJU Exhaust Gas - -