Honda Accord 2008 Manual page 359

07/11/02 09:00:45 61TA0000_110_0040
Fuel and Emissions Systems
System Description (cont'd)
VTEC System
Intake valve side (All models)
• 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.
• The rocker arm oil control solenoid (rocker arm oil control solenoid A) switches the intake valve side of the VTEC
system on and off; the solenoid is controlled by the ECM/PCM.
• The rocker arm oil pressure switch (rocker arm oil pressure switch A) detects VTEC system oil pressure (intake valve
side) and sends this information to the ECM/PCM.
Exhaust valve side (PZEV model)
• The VTEC system switches the operation of one of the exhaust valves to pause and lift the valve.
• At idle and low engine speed, one side of the exhaust valves is paused, and the valve lifts when the engine speed
goes up.
• The system reduces hydrocarbons (HC) exhaust emissions at low engine speed.
• Rocker arm oil control solenoid B switches the exhaust valve side of the VTEC system on and off; the solenoid is
controlled by the PCM.
• Rocker arm oil pressure switch B detects the VTEC system oil pressure (exhaust valve side), and sends this
information to the PCM.
All models expect PZEV (Intake valve VTEC)
ENGINE SPEED
HIGH
＊３２
EX
EX
11-40
ROCKER ARM OIL CONTROL
SOLENOID
LOW OFF
ON
LOW ENGINE SPEED
HIGH ENGINE SPEED
ROCKER ARM OIL PRESSURE
SWITCH
ON
OFF
ROCKER ARM
OIL PRESSURE
SWITCH
IN (LOW LIFT)
IN (HIGH LIFT)
INTAKE VALVE LIFT
LOW
HIGH
ROCKER ARM
OIL CONTROL VALVE
(All models except PZEV)
ROCKER ARM
OIL CONTROL
SOLENOID