SFI SYSTEM


  1. FUNCTION


    1. The Dual Variable Valve Timing-intelligent (VVT-i) system is designed to control the intake and exhaust camshafts within a range of 56° and 30° respectively (of crankshaft angle) to provide valve timing that is optimally suited to the engine operating conditions. This improves torque in all speed ranges as well as increasing fuel economy, and reducing exhaust emissions.

    2. For the intake valves, the Variable Valve Timing-intelligent by Electric motor (VVT-iE) uses electric motors to control the valve timing. Because VVT-iE is actuated by electric motors, it can perform optimal valve timing control even when the engine oil pressure is low, such as when the engine oil temperature or the engine speed is low. For conventional VVT-i, the maximum retarded valve timing during engine operation is determined by the retarded valve timing required when starting the engine. Because this system can control the valve timing during startup, it is possible to further increase the maximum retarded valve timing as the maximum retarded valve timing is no longer limited by the timing required to start the engine.

    3. The exhaust side has VVT-i that uses engine oil pressure to control the valve timing.

    4. The dual VVT-i system delivers excellent benefits in the different operating conditions as shown in the table below.


      1. During Idling

        A01FJFXE01
        *1 TDC
        *2 Earliest (EX)
        *3 Neutral (IN)
        *4 BDC
        Objective Effect
        Eliminating overlap reduces blow back to the intake side.

        • Stabilized idle speed

        • Better fuel economy

      2. In Low Speed Range with Light to Medium Load

        A01FJCKE01
        *1 TDC
        *2 To Retard Side (EX)
        *3 To Retard Side (IN)
        *4 BDC
        Objective Effect

        • Retarding the intake valve closing timing to reduce pumping losses.

        • Increasing overlap to increase internal EGR.

        • Better fuel economy

        • Improved emission control

      3. In Low to Medium Speed Range with Heavy Load

        A01FJT8E01
        *1 TDC
        *2 To Advance Side (EX)
        *3 To Advance Side (IN)
        *4 BDC
        Objective Effect
        Advancing the intake valve closing timing improves volumetric efficiency. Improved torque in low to medium speed range

      4. In High Speed Range with Heavy Load

        A01FJCZE01
        *1 To Advance Side (EX)
        *2 TDC
        *3 To Retard Side (IN)
        *4 BDC
        Objective Effect
        Retarding the intake valve closing timing improves volumetric efficiency. Improved output

      5. At Low Temperatures

        A01FJFXE01
        *1 TDC
        *2 Earliest (EX)
        *3 Neutral (IN)
        *4 BDC
        Objective Effect
        Eliminating overlap reduces blow back to the intake side to stabilize the idle speed during fast idle.

        • Stabilized fast idle speed

        • Better fuel economy

      6. Starting the Engine/Stopping the Engine

        A01FJFXE01
        *1 TDC
        *2 Earliest (EX)
        *3 Neutral (IN)
        *4 BDC
        Objective Effect
        Eliminating overlap reduces blow back to the intake side. Improved startability