SFI SYSTEM


  1. OPERATION


    1. Based on engine speed, intake air volume, throttle position and engine coolant temperature, the ECM calculates optimal valve timing for all driving conditions. The ECM also controls the camshaft timing oil control valve assemblies. In addition, the ECM uses signals from the camshaft position sensors and the crank position sensor to detect the actual valve timing, thus providing feedback control to achieve the target valve timing.

      B0022VWE08

    2. When the camshaft timing oil control valve assembly is positioned as shown in the illustration below by the by the advance signal from the ECM the resultant oil pressure is applied to the timing advance side vane chamber to rotate the camshaft in the timing advance direction.

      B0022UIC01
      *A Advance Side Operation (Intake Side) *B Advance Side Operation (Exhaust Side)
      *1 Vane - -
      *a Rotation Direction *b Oil Pressure
      *c In *d Drain

    3. When the camshaft timing oil control valve assembly is positioned as shown in the illustration below by the retard signals from the ECM, the resultant oil pressure is applied to the timing retard side vane chamber to rotate the camshaft in the timing retard direction.

      B0023B6C01
      *A Retard Side Operation (Intake Side) *B Retard Side Operation (Exhaust Side)
      *1 Vane - -
      *a Rotation Direction *b Oil Pressure
      *c In *d Drain

    4. After reaching the target timing, the engine valve timing is maintained by keeping the camshaft timing oil control valve assembly in the neutral position unless the engine operating conditions change. This maintains the engine valve timing at the desired target position by preventing the engine oil from running out of the camshaft timing oil control valve assembly.