Variable Valve Timing: Description and Operation

GF05.20-P-2100MAR Adjustable Camshaft Timing Solenoid, Component Description
ENGINES 156.981 in MODEL 230.470 as of Model Year 09 /Modification Year 08 model refinement package





View of the engine from the front

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
Die solenoids actuate the camshaft adjustment, which allows all camshafts to be displaced continuously by up to 42° crank angle.
Camshaft adjustment optimizes engine torque characteristics and improves exhaust characteristics.

Design
The solenoids are designed as proportional solenoids, i.e. the armature travel - and therefore the position of the control plunger in the integrated control valve - depends on the strength of current in the coil.

Function
The solenoids are actuated at the ground end by a PWM signal from the ME-SFI control unit (N3/10). Voltage is supplied to the solenoid through "circuit 87 M1".
The integral control plungers are actuated via the map-dependent duty cycle of the PWM signal. To achieve rapid adjustment of the armature, the maximum current (duty cycle 100 %) is output for a short period (approx. 0.5 sec). Then a hold-in winding voltage with a lower duty cycle is set.

Through the duty cycle, the solenoids actuate the control plungers in the control valves, which causes more or less switching oil (pressure oil) to flow in the swivel motor adjusters.
The quantity of pressure oil in the swivel motor adjusters is controlled according to the positions of the control plungers. This is achieved by bore holes located at various points in the control valves as well as by oil ducts in the swivel motor adjuster rotors.

The camshaft adjustment range is mechanically restricted by the shape of the swivel motor adjuster. If the solenoids are no longer actuated then a rest occurs against the direction of rotation in which the camshafts are mechanically locked (start position).





Camshaft adjustment (LH exhaust camshaft)

1 Left exhaust camshaft housing
1/1 Switching oil ducts to switching oil pilot bushing
1/2 Solenoid
1/3 Switching oil control valve
2 Switching oil pilot bushing
2/1 Pulse wheel of exhaust camshaft
3 Swivel motor adjuster
4 Exhaust camshaft

B6/6 Left exhaust camshaft Hall sensor
Y49/6 Left exhaust camshaft solenoid