EMISSION CONTROL SYSTEM


  1. FUNCTION OF MAIN COMPONENTS


    1. The main components of the 1NZ-FXE emission control system are as follows.

      Component Function
      TWC

      Oxidizes CO and HC in the exhaust gas and deoxidizes NOx at the same time, to purify them into CO2, H2O and N2.
      Oxygen Sensor This sensor detects the oxygen concentration in the exhaust emission by measuring the electromotive force which is generated in the sensor itself.
      Air Fuel Ratio Sensor As with the oxygen sensor, this sensor detects the oxygen concentration in the exhaust gas. However, it detects the oxygen concentration in the exhaust gas linearly.
      E.F.I. Vacuum Sensor Assembly Uses built-in semiconductors to detect the intake manifold pressure.
      EGR Valve Assembly Operates when receiving signals from the ECM, regulating the EGR volume.
      EGR Cooler Assembly Cools the exhaust gas temperature to improve the EGR efficiency.
      Ventilation Valve Sub-assembly Opens and closes using vacuum generated in the intake manifold and controls the flow rate of the blowby gas.
      Charcoal Canister Contains activated charcoal to absorb the fuel vapors that are created in the fuel tank assembly.
      Purge VSV Opens in accordance with the signals from the ECM when the system is purging, in order to send the fuel vapor that was absorbed by the charcoal canister into the intake manifold.
      ECM

      • Controls the volume of fuel injected, with corrections based primarily on the signal from the air fuel ratio sensor, and 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.

      • Controls the purge VSV in accordance with the signals from various sensors, in order to achieve a purge volume that suits the driving conditions.

  2. SYSTEM CONTROL


    1. EGR Control


      1. For the EGR system, a regulated amount of inert gas is allowed to flow into the intake passage, reducing the peak temperature in the engine combustion chamber.

      2. By sensing the engine driving conditions, the ECM operates the EGR valve assembly and throttle control motor, to regulate the amount of exhaust gas that is recirculated.

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    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 ventilation valve sub-assembly 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 ventilation valve sub-assembly side passage due to the intake manifold vacuum.

        A01UX2TE09
        Text in Illustration
        *1 Ventilation Valve Sub-assembly - -
        *a When load is low *b When load is high
        A01UWXO Blowby Gas A01UX3T Fresh Air

  3. CONSTRUCTION


    1. Three-Way Catalytic converter (TWC)


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

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

      3. These TWCs enable improved exhaust emissions with an optimized cell density and wall thickness.

        A01UX2RE03
        Text in Illustration
        *1 TWC - -

    2. EGR Valve Assembly and EGR Cooler Assembly


      1. A step motor type EGR valve assembly is used to precisely control the EGR gas flow amount.

      2. The EGR cooler assembly cools the exhaust gas to improve the EGR efficiency.

        A01UX30E04
        Text in Illustration
        *1 Water Passage *2 EGR Gas Passage
        *3 EGR Valve Assembly *4 No. 2 EGR Pipe
        *5 EGR Cooler Assembly *6 No. 1 EGR Pipe
        *a To Intake Manifold *b From Exhaust Manifold
        *c A-A Cross Section - -
        A01UWXO EGR Gas - -

    3. E.F.I. Vacuum Sensor Assembly


      1. An E.F.I. vacuum sensor assembly is used to measure the intake manifold pressure for EGR control.

      2. The E.F.I. vacuum sensor assembly consists of a silicon chip which utilizes the characteristic of a silicon chip that changes its electrical resistance when pressure is applied to it. The sensor converts the pressure into an electrical signal, and sends it to the ECM in an amplified form.

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