Variable Valve Timing: Description and Operation

GF05.20-P-2100MIR Adjustable Camshaft Timing Solenoid, Component Description
ENGINES 272.949 in MODEL 230.454 as of Model Year 09 /Modification Year 08 model refinement package
ENGINES 272.968 in MODEL 230.458 as of Model Year 09 /Modification Year 08 model refinement package
ENGINES 273.965 in MODEL 230.471 as of Model Year 09 /Modification Year 08 model refinement package





View of right and left cylinder head

Y49/4 Left intake camshaft solenoid
Y49/5 Right intake camshaft solenoid
Y49/6 Left exhaust camshaft solenoid
Y49/7 Right exhaust camshaft solenoid

Location
The solenoids are located in front of the camshaft at the front of the cylinder head.

Task
The solenoids actuate the vane-cell adjuster control plungers which in turn adjust the camshafts.

Design
The solenoids are designed as proportional solenoids, i.e. the armature travel, and therefore the position of the control plunger in the vane-cell adjuster depends on the level of current in the coil.





Function

1 Pulse wheel for right intake camshaft
2 Vane-cell adjuster for right intake camshaft
3 Control plunger for left exhaust camshaft

B6/4 Left intake camshaft Hall sensor
B6/5 Right intake camshaft Hall sensor
B6/6 Left exhaust camshaft Hall sensor
B6/7 Right exhaust camshaft Hall sensor

Y49/4 Left intake camshaft solenoid
Y49/5 Right intake camshaft solenoid
Y49/6 Left exhaust camshaft solenoid
Y49/7 Right exhaust camshaft solenoid

The solenoids are actuated at the ground end by a PWM signal from the ME-SFI control unit (N3/10). The frequency of the PWM signal is 150 Hz. The vane-cell adjuster control plunger are actuated via the map-dependent duty cycle of the PWM signal. For rapid adjustment of the camshafts the duty cycle of 100% (maximum current strength) is issued for a short time (about 0.5 s). A hold-in winding voltage with a smaller duty cycle is then set (lower current strength).
Depending on the positions of the control plungers, more or less pressure oil flows out of the hollow camshafts into the oil galleries of the vane-cell adjusters. This is achieved by bore holes located at various points on the control plungers and by oil ducts in the vane cell adjusters. The vane-cell adjusters adjust the camshafts according to their filling with pressure oil. If the solenoids are no longer actuated, a mechanical reset against the direction of rotation takes place.

The camshaft adjustment range is mechanically restricted by the shape of the vane-cell adjuster.

The following positions of the control plunger are possible:

Fill oil galleries
Pressure oil flows from the hollow camshafts into the vane-cell adjuster. The camshafts adjust to the respective direction of rotation. The intake camshafts adjust to "advanced". The exhaust camshafts adjust due to their reverse direction of rotation to "retarded".

Close off oil galleries.
A camshaft Hall sensor detects the camshaft positions of each camshaft. If the required adjustment is obtained, the respective solenoid is actuated so that the oil galleries in the vane-cell adjusters are closed.

Empty the oil galleries
The camshafts are adjusted mechanically against the direction of rotation.