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Home >> Kia >> 2017 >> Optima EX >> Repair and Diagnosis (Single Page) >> Engine Mechanical >> Auxiliary Emission Control Systems >> Exhaust Emission Control System - 2.4L (Except HEV) >> CVVT (Continuously Variable Valve Timing) System >> Description and Operation >> Operation Principle >> [CVVT System Mode]

[CVVT System Mode]

Fig 1: CVVT System Mode Graph (1 Of 2)
G12146785Courtesy of KIA MOTORS AMERICA, INC.
Fig 2: CVVT System Mode Graph (2 Of 2)
G12146786Courtesy of KIA MOTORS AMERICA, INC.
Driving Condition Exhaust Valve Intake Valve
Valve Timing Effect Valve Timing Effect
(1) Low Speed/Low Load Completely Advance *Valve Under-lap
*Improvement of combustion stability
*Increase of expansion work		 Completely Retard *Valve Under-lap
(2) Part Load Retard *Reduction of pumping loss
*Reduction of HC		 Retard *Reduction of pumping loss
- Retard *Increase of expansion work Advance -
(3) Low Speed/High Load - - - *Prevention of intake back flow (Improvement of volumetric efficiency)
(4) High Speed/High Load Advance *Reduction of pumping loss Retard *Improvement of volumetric efficiency
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