Acura CSX. Manual - part 91
２８
１１
１１
VTC System
VTEC System
K20Z2 engine
K20Z3 engine
11-38
Fuel and Emissions Systems
MAXIMUM VTC ADVANCE 25 °
TDC
EX
IN 1
IN 2
EX
IN 2
IN 1
MAXIMUM VTC ADVANCE 25 °
SHORT OVERLAP
LONG OVERLAP
LOW SPEED VALVE TIMING
HIGH SPEED VALVE TIMING
EX
IN
EX
IN
IN (LOW LIFT)
LOW SPEED VALVE TIMING
HIGH SPEED VALVE TIMING
EX
IN
EX
IN
• The VTC 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 charging effect.
• The system reduces the cam advance at idle, stabilizes combustion, and reduces engine speed.
• If a malfunction occurs, the VTC system control is disabled and the valve timing is fixed at the fully retarded position.
• The VTEC system changes the cam profile to correspond to the engine speed. It maximizes torque at low engine
speed and output at high engine speed.
• The low lift cam is used at low engine speeds, and the high lift cam is used at high engine speeds.
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