Variable Cylinder Management (VCM)/VTC System Description (3.0L Engine)
For locations of each component on the vehicle, refer to the Component Location Index - Refer to: Fuel and Emissions Systems Component Location Index(Mexico models) or Fuel and Emissions Systems Component Location Index(Mexico models) .
Overview (VCM System)
The Variable Cylinder Management (VCM) system switches the operating cylinder between 6 cylinder operation and 3 cylinder operation depending on the driving conditions. The VCM system installed for the rear bank stops opening and closing the intake and exhaust valves when the 3 cylinder mode is activated. Not opening and closing the valves eliminates the drive resistance (valve spring compression resistance) for valve opening, closing and the suction air resistance (pumping loss), which leads to a reduction of engine rotation resistance.
Overview (VTC System)
The VTC system makes continuous changes to each bank's intake and exhaust valve timing depending on the engine speed, engine load, and vehicle speed.
Construction
The VCM system is installed on the rear bank and is composed of each valve lifter with the switching piston, the rocker arm oil control valve, and the oil passage on the cylinder head. The VTC system acts on the camshafts of each bank, and is composed of the VTC actuator, the VTC oil control valve, and the oil passage of each cylinder head and camshaft.
Control
The VCM system and the VTC system diagram is as follows. The PCM controls the rocker arm oil control solenoid and VTC oil control solenoid valves based on data from various sensors. Also, the PCM calculates the optimum VTC angle based on the operating status of the VCM system.
VCM System
VTC System
Rocker Arm Oil Pressure Sensor
The rocker arm oil pressure sensor monitors the oil pressure of the 6 cylinder mode oil passage in the rocker arm oil control valve. The PCM determines the failure of the VCM system based on the status of the command signal to the rocker arm oil control solenoid and the rocker arm oil pressure sensor signal.
| VCM System Operation Mode | Rocker Arm Oil Control Solenoid | Rocker Arm Oil Pressure Sensor |
|---|---|---|
| 6 Cylinder Mode | OFF | High Pressure |
| 3 Cylinder Mode | ON | Low Pressure |
Operation (VCM System)
6 Cylinder Mode
The rocker arm oil control solenoid is turned OFF by the PCM. Oil pressure from the rocker arm oil control solenoid enters the return spring side of the valve lifter via the oil passage of the cylinder head, and the switching piston of the valve lifter is pushed by the oil pressure and the return spring tension. Each rocker arm is pushed by the camshaft, and the rocker arm lifts the valve via the switching piston of the valve lifter.
3 Cylinder Mode
The rocker arm oil control solenoid is turned ON by the PCM. Oil pressure from the rocker arm oil control solenoid enters the switching piston side of the valve lifter via the oil passage of the cylinder head, and the switching piston is pushed by the oil pressure. Each rocker arm is pushed by the camshaft, but even if the rocker arm pushes the valve lifter, the rear end of the valve enters the hole in the switching piston of the valve lifter, so each valve pauses without being pushed.
Operation (VTC System)
Advance Rotation Operation
When the advance chamber is charged with pressured oil from the VTC oil control solenoid valve, the camshaft rotates to the advanced side. When there is no oil pressure (engine is stopped), the VTC actuator B is locked in the most advanced position by the return spring and the lock pin.
Intake Side (VTC Actuator A, VTC Oil Control Solenoid Valve A)
Exhaust Side (VTC Actuator B, VTC Oil Control Solenoid Valve B)
Retard Rotation Operation
When the retard chamber is charged with pressured oil from the VTC oil control solenoid valve, the camshaft rotates to the retarded side. When there is no oil pressure (engine is stopped), the VTC actuator A is locked in the most retarded position by the lock pin.
Intake Side (VTC Actuator A, VTC Oil Control Solenoid Valve A)
Exhaust Side (VTC Actuator B, VTC Oil Control Solenoid Valve B)