SFI SYSTEM CONTROL DUAL VVT-i CONTROL

FUNCTION

1. The Dual Variable Valve Timing-intelligent (Dual VVT-i) system is designed to control the intake and exhaust camshafts within a range of 41° and 45° respectively (of crankshaft angle) to provide valve timing that is optimally suited to engine operating conditions. This improves torque in all speed ranges as well as increasing fuel economy and reducing exhaust emissions.

   

   

   *a	VVT-i Operation Range (Intake)	*b	VVT-i Operation Range (Exhaust)
   *c	TDC	*d	BDC
   	Exhaust Valve Opening Angle		Intake Valve Opening Angle

2. The Dual VVT-i system delivers excellent benefit in vehicle states as shown in the table below.

   • During Idle

     

     Objective	Effect
     Eliminating overlap to reduce blowback to the intake side.	Stabilized idle speed Better fuel economy

   • At Light Load

     

     Objective	Effect
     Eliminating overlap to reduce blowback to the intake side.	Ensures engine stability

   • At Medium Load

     

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

   • 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

   • In High Speed Range with Heavy Load

     

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

   • At Low Temperatures

     

     Objective	Effect
     Eliminating overlap to reduce blowback to the intake side stabilizes the idle speed during fast idle.	Stabilized idle speed Better fuel economy

   • Upon Starting the Engine/Upon Stopping the Engine

     

     Objective	Effect
     Eliminating overlap to minimize blowback to the intake side.	Improved startability