Vtc System - Honda Civic 2002-2003 Service Manual

Fuel and Emissions Systems
System Descriptions (cont'd)
VTCsystem
• 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 the pumping loss. The intake valve is closed quickly to
reduce the entry afthe air/fuel mixture into the intake port and improve the charging effect.
Cam angle is reduced at idle to stabilize 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.
TDC
MAXIMUM VTC ADVANCE 50 0
_ . _ - .
MAXIMUM VTC ADVANCE 50
0
EX
",'
4t---1~~'
SHORT OVERLAP
,
,
,
.. '
4t-----1.~' LONG OVERLAP
VTEC system
• The VTEC system changes the cam profile to correspond to 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.
LOW SPEED VALVE TIMING HIGH SPEED VALVE TIMING
IN
11-30