Continuously Variable Valve Timing (CVVT) System: Operation

• The CVVT system makes continuous intake valve timing changes based on operating conditions.
• Intake valve timing is optimized to allow the engine to produce maximum power.
• Cam angle is advanced to obtain the EGR effect and reduce pumping loss. The intake valve is closed quickly to reduce the entry of the air/fuel mixture into the intake port and improve the changing effect.
• Reduces the cam advance at idle, stabilizes combustion, and reduces engine speed.
• If a malfunction occurs, the CVVT system control is disabled and the valve timing is fixed at the fully retarded position.
  Fig 1: Illustrating CVVT Operation

  Courtesy of KIA MOTORS AMERICA, INC.

1. The previous figure shows the relative operation structures of the housing vane to the rotor vane.
2. If the CVVT is held a certain control angle, to hold this state, oil is replenished as much as oil leaks from the oil pump.

The OCV (Oil-flow Control Valve) spool location at this time is as follows.

Oil pump --> Advance oil chamber (Little by little open the inflow side to the advance oil chamber) --> Almost close the drain side 

Be sure there might be a difference in the position according to the engine running state (RPM, oil temperature, and oil pressure).