Mazda 6 Training Manual page 35

VALVE MECHANISM
Outline
• A variable timing mechanism, which realizes optimum valve timing according to engine operation conditions by
continuously modifying the phases of the intake camshaft and crankshaft, has been adopted.
.
1 Torque
2 Engine speed
3 Low-middle speed engine
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 NO the in
ehaust 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 maimum
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.
VALVE MECHANISM
4 High speed engine
5 Engine with variable valve timing mechanism
A6E221112111T07
B
AME2211N013
B–27