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Camshaft Adjustment, Function - GF07.10-P-1016MNL

Engine 176.9, 177.9 in model 217 

Engine 176.9, 177.9 in model 222 

Engine 177.9 in model 290 

up to model year 2021 

Function requirements for camshaft adjustment, general points 

Camshaft adjustment, general points 

Through camshaft adjustment all four camshaft can be adjusted continuously up to a 40° KW (CKA) and therefore the valve overlap for charge change can be varied within wide limits.

This optimizes engine torque characteristics and improves the exhaust characteristics.

IMPORTANT Valve overlap

The intake valves open before the exhaust valves close.

For camshaft adjustment the ME-SFi [ME] control unit (N3/10) reads in the following signals for camshaft adjustment:

Function sequence for camshaft adjustment 

Function sequence for release of the camshaft adjustment 

Camshaft adjustment is enabled by the ME-SFI control unit dependent on engine speed and engine oil temperature.

IMPORTANT The engine oil temperature is important, even when the oil is hot, to ensure that there is sufficient oil pressure (> 1.5 bar) for adjusting the camshafts.

Release of adjustment of the exhaust camshafts takes place by means of a comparison to the intake camshafts, at first at a high rotational speed. In this way for exhaust, also at a low oil pressure level, reaching the locking position against the "retard" operating reaction torques of the camshaft are secured.

There is a return spring located for support in each camshaft positioner.

If all four camshafts are adjusted, adjustment of the exhaust camshafts takes place after a delay (later). Oil supply problems are prevented and secure functioning of the locking mechanism achieved.

Release of the camshaft adjustment occurs load-dependent:

Function sequence for oil pressure 

The engine oil pressure is regulated via the engine oil pump valve (Y130) in order to ensure an adequate oil supply and to lower the oil pressure if necessary (a saving on fuel).

Function sequence for adjustment 

The left and right intake camshaft solenoids (Y49/4, Y49/5) and the left and right exhaust camshaft solenoids (Y49/6, Y49/7) are actuated by the ME-SFI control unit by means of a pulse width modulated signal. The control plungers are adjusted via the characteristics map-dependent duty cycle. The oil filling capacities (engine oil) for the camshaft positioners are controlled according to their position. The vane pistons which are firmly connected to the camshafts are thus turned by the engine oil in the camshaft positioners.

Start position: 

The camshafts are locked in a fixed position for starting by catch bolts (locked). This start position is unlocked hydraulically at the first actuation of the left and right intake camshaft and exhaust camshaft solenoids.

Setting range: 

Shown is oil flows in the intake camshaft camshaft positioner 

G15299176Courtesy of MERCEDES-BENZ USA

The upper half of the illustration shows: 

Fill the pressure chamber for retarding the ignition timing (A), pressure chamber for timing advance (B) open

The lower half of the illustration shows: 

Fill the pressure chamber for timing advance (B), pressure chamber for retarding the ignition timing (B) open

Function sequence for valve overlap 

At low engine speed and load, the ME-SFI control unit sets a large valve overlap in order to produce internal exhaust gas recirculation. Less fresh air is admitted, as exhaust gases with low oxygen content are still present in the cylinders. This lowers the combustion temperature and reduces the formation of nitrogen oxides (NOX ).

The intake air mass is reduced by the amount of exhaust gases present. The ME-SFI control unit shortens the injection period accordingly.

The smallest valve overlap for gas exchange occurs if the exhaust camshaft are adjusted to the maximum BTDC (advanced) and the intake camshaft to the maximum ATDC (retarded). The resulting increased fresh gas content produces more engine torque and engine output.

Function sequence for camshaft positions monitoring 

The camshafts positions are detected by the intake camshaft Hall sensors and the exhaust camshaft Hall sensors, and communicated to the ME-SFI control unit. Acquisition of the positions takes place through detection of the positions of pulse wheels which are located at the front on the camshafts.

Function sequence: diagnosis 

During diagnosis of the camshaft adjustment, the ME-SFI control unit checks whether the camshafts are in start position at engine start and whether the requested adjustment has been reached after the engine has been running for a short time. Output stage errors in the camshaft solenoids (integrated with the ME-SFI control unit) and defective camshaft Hall sensors are also detected.

Shown: intake camshaft adjustment 

G15299177Courtesy of MERCEDES-BENZ USA

Shown: intake camshaft camshaft positioner 

G15299178Courtesy of MERCEDES-BENZ USA
  Electrical function schematic for camshaft adjustment Engine 177.9 in model 290 up to model year 2021 PE07.10-P-2716-97XBA
    Engine 176.9, 177.9 in model 217Engine 176.9, 177.9 in model 222 PE07.10-P-2716-97SEL
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