Variable Valve Timing: Description and Operation

GF05.20-P-2100AMG Adjustable Camshaft Timing Solenoid, Component Description
ENGINE 156.980 in MODEL 164, 251 up to Model Year 8
ENGINE 156.982 in MODEL 209
ENGINE 156.983 in MODEL 211, 219
ENGINE 156.984 in MODEL 216, 221 up to Model Year 8





Location

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 camshaft solenoids are located at the front on respective cylinder head.

Task
The camshaft solenoids actuate camshaft adjustment, whereby camshafts are continuously adjusted up a 42° crank angle.
Adjustment of camshaft optimizes engine torque development and improves exhaust characteristics.

Design
Solenoids are designed as proportional solenoids which means travel of the anchor and thus the location of the control plunger in the integral control valve is dependent on the current strength in the coil.

Function
Solenoids are actuated at the ground end by the ME-SFI [ME] control unit (N3/10) by means of a PWM signal (pulse width modulated signal). The voltage supply to the solenoid is via "terminal 87".
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.

Solenoid actuate via the duty cycle of control plunger in control valves whereby more or less switching oil (pressure oil) flows in the swivel motor adjuster.
The amount of switching oil in swivel motor adjuster is controlled according to the position of control plunger. 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 (left 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 Exhaust camshaft pulse wheel
3 Swivel motor adjuster
4 Exhaust camshaft

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





Swivel motor adjuster

3/1 Torx screws
3/2 Front cover
3/3 Catch bolt with spring and spring cup
3/4 Rotor
3/5 Stator
3/6 Dowel pin
3/7 Rear cover
3/8 Front gearwheel (main toothed wheel)
3/9 Front gearwheel (tensioning wheel)
3/10 Springs (gear backlash compensation)
3/11 Fixing screw M5 x8 (for disassembly and assembly of swivel motor adjuster)
3/12 Circlip (gear backlash compensation)