MECHANICAL
01–10–15
01–10
Variable Valve Timing Mechanism
Function
• The variable valve timing mechanism continuously modifies the phases of the variable valve timing actuator
and the intake camshaft using hydraulic pressure controlled by the oil control valve (OCV) so that optimal valve
timing is obtained according to engine operation conditions.
• The oil control valve (OCV) operation is based on signals from the PCM according to engine operation
conditions and it controls hydraulic pressure to the variable valve timing actuator.
Operation and purpose according to driving condition
Idling range, light load range
• Due to a reduction in the amount of overlap, less combusted gas is returned to the intake port. This stabilizes
idle speed in the idling range, improving fuel economy, and also ensures engine stability in the light load range.
Medium load range
• Overlap amount has been increased and the EGR ratio inside the cylinder is higher. This reduces engine
friction loss (pumping loss), lowering the combustion temperature and reducing the amount of NOx the in
exhaust gas. The amount of hydrocarbon emission has also been reduced through reignition of non-combusted
gas.
Heavy load, low-middle speed range
• The intake valve is closed early, and high volumetric efficiency is obtained to improve low-middle speed torque.
Heavy load, high speed range
• Timing for intake valve closure is delayed and high volumetric efficiency is obtained to improve maximum
output.
When temperature is low
• The overlap amount has been minimized to prevent combusted gas from returning to the intake port and to
reduce the additional fuel injection amount. This improves fuel economy and stabilizes fast idle speed.
When engine is started or stopped
• Startability has been improved because the overlap amount has been minimized to prevent combusted gas
from returning to the intake port.
LOAD
ENGINE SPEED
IDLING RANGE
LIGHT LOAD RANGE
MEDIUM LOAD RANGE
HEAVY LOAD, LOW-MIDDLE
SPEED RANGE
HEAVY LOAD, HIGH SPEED RANGE
FULL LOAD PERFORMANCE
E5U110ZT5022
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