SFI SYSTEM CONTROL VVT-i CONTROL

FUNCTION

1. The Variable Valve Timing-intelligent (VVT-i) system is designed to control the intake camshaft within a range of 45° (of crankshaft angle) to provide valve timing that is optimally suited to the engine condition. This improves torque in all the speed ranges as well as increasing fuel economy, and reducing exhaust emissions.

   

   *1	Camshaft Position Sensor	*2	Engine Coolant Temperature Sensor
   *3	Camshaft Timing Oil Control Valve Assembly	*4	Crank Position Sensor
   *5	ECM	-	-
   *a	From Vacuum Sensor Assembly	*b	From Throttle Position Sensor

   

2. The VVT-i system delivers excellent benefits during different vehicle operation states as shown in the table below.

   1. During Idling

      

      Objective	Effect
      Decreasing overlap to reduce blow back to the intake side.	Stabilized idle speed Better fuel economy

   2. At Light Load

      

      Objective	Effect
      Decreasing overlap to reduce blow back to the intake side.	Ensured engine stability

   3. At Medium Load

      

      Objective	Effect
      Increasing overlap to increase internal EGR to reduce pumping loss.	Better fuel economy Improved emission control

   4. In Low to Medium Speed Range with Heavy Load

      

      Objective	Effect
      Advancing the intake valve close timing for volumetric efficiency improvement.	Improved torque in low to medium speed range

   5. In High Speed Range with Heavy Load

      

      Objective	Effect
      Retarding the intake valve close timing for volumetric efficiency improvement.	Improved output

   6. At Low Temperatures

      

      Objective	Effect
      Eliminating overlap to reduce blow back to the intake side leads to a lean condition and stabilizes the idle speed at fast idle.	Stabilized fast idle speed Better fuel economy

   7. Upon Starting / Stopping the Engine

      

      Objective	Effect
      Eliminate overlap to reduce blow back to the intake side.	Improved startability