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Home >> Kia >> 2020 >> Optima Plug-In Hybrid EX >> Repair and Diagnosis >> Engine Mechanical >> Auxiliary Emission Control Systems >> Exhaust Emission Control System (PHEV) >> CVVT (Continuously Variable Valve Timing) System >> Description & Operation >> Operation Principle >> CVVT System Mode

CVVT System Mode

G13361613Courtesy of KIA MOTORS AMERICA, INC.
G13361614Courtesy 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		 Completely Retard * Valve Under-lap
* Improvement of combustion stability
(2) Part Load Retard * Increase of expansion work
* Reduction of pumping loss
* Reduction of HC		 Retard * Reduction of pumping loss
(3) Low Speed/High Load Retard * Increase of expansion work Advance * 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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