Camshaft Adjustment, Function - GF07.10-P-1016MNA
Engine 177.9 in model 205, 253
Engine 177.9 in model 213
up to model year 2021
Function requirements, general
- Engine runs
The ME-SFI [ME] control unit (N3/10) detects that the engine is running by interpreting the signals from the crankshaft Hall sensor (B70). The ME-SFI [ME] control unit directly reads in the signals of the crankshaft Hall sensor.
Camshaft adjustment, general points
With camshaft adjustment, all four camshafts can be continuously adjusted by up to 40°. The valve overlap can be adjusted over a wide range in the event of gas exchange. This optimizes engine torque characteristics and improves the exhaust characteristics.
Valve overlap
The intake valves open before the exhaust valves close.
For camshaft adjustment, the ME-SFI [ME] control unit reads in signals from the following component parts:
- Engine oil temperature sensor (B1)
- Left intake camshaft Hall sensor (B6/4)
- Right intake camshaft Hall sensor (B6/5)
- Left exhaust camshaft Hall sensor (B6/6)
- Right exhaust camshaft Hall sensor (B6/7)
- Coolant temperature sensor (B11/4)
- Pressure sensor downstream of left throttle valve (B28/22)
- Pressure sensor downstream of right throttle valve (B28/23)
- Oil sensor (oil level, temperature and quality) (B40)
- Crankshaft Hall sensor
Camshaft adjustment is enabled by the ME-SFI [ME] control unit, depending on the engine speed and the engine oil temperature. Compared to enabling adjustment of the intake camshafts, enabling the adjustment of the exhaust camshafts does not take place until a higher rotational speed is reached. This ensures that the locking position against the reaction torques of the exhaust camshafts with the "retarded" effect is also reached at low oil pressure. A return spring is integrated into each camshaft positioner.
If all four camshafts are to be adjusted, the exhaust camshafts are adjusted after a delay (later). This prevents oil supply problems, and reliable operation of the locking mechanisms is guaranteed.
The oil pressure is regulated via the engine oil pump valve (Y130).
The ME-SFI [ME] control unit actuates the engine oil pump valve directly.
Release of the camshaft adjustment occurs load-dependent:
- For an engine oil temperature of 80°C from about 600 RPM
- For an engine oil temperature of 120°C (intake side) from about 800 RPM
- For an engine oil temperature of 120°C (exhaust side) from about 1050 RPM
The ME-SFI [ME] control unit actuates the following components for camshaft adjustment:
- Left intake camshaft solenoid (Y49/4)
- Right intake camshaft solenoid (Y49/5)
- Left exhaust camshaft solenoid (Y49/6)
- Right exhaust camshaft solenoid (Y49/7)
The ME-SFI [ME] control unit actuates the solenoids with a pulse width modulated signal. The oil volume flow for the camshaft positioners is applied using control plungers. The vane pistons, which are firmly connected to the camshafts, are turned by the in-flowing oil volume. In order to diagnose the camshaft adjustment, the ME-SFI [ME] 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 faults of the solenoids and defective Hall sensors are also detected.
Shown on camshaft with camshaft positioner
Shown on camshaft positioner
Adjustment range
Intake camshaft: 5° BTDC (top dead center) up to 35° ATDC (intake opens)
Exhaust camshaft: 32° BTDC up to 8° ATDC (exhaust closes)
Start position
The camshafts are held in a defined position by catch bolts (locked) for starting the engine. This lock is hydraulically unlocked when the first actuation of the solenoids takes place.
Intake camshaft: 35° ATDC (intake opens)
Exhaust camshaft: 32° BTDC (exhaust closes)
Shown is oil flows in the intake camshaft positioner
The upper half of the figure shows the filling of the fluid reservoirs (A), the fluid reservoirs (B) are unblocked.
The lower half of the figure shows the filling of the fluid reservoirs (B), the fluid reservoirs (A) are unblocked.
At low engine speed and load, the ME-SFI [ME] 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. The combustion temperature drops, and the formation of nitrogen oxides (NO x) is reduced.
The intake air mass is reduced by the amount of exhaust gases present. The ME-SFI [ME] control unit shortens the injection period accordingly.
The smallest valve overlap during a gas exchange occurs if the exhaust camshafts are set to the maximum BTDC (advanced) and the intake camshafts are set to the maximum ATDC (retarded). The resulting increased fresh air content produces more engine torque and engine power.
| Electrical function schematic for camshaft adjustment | Engine 177.9 in model 205, 253 | PE07.10-P-2716-97FBD | |
| Engine 177.9 in model 213 up to model year 2021 | PE07.10-P-2716-97DBG | ||
| Overview of system components for gasoline injection and ignition system with direct injection | Engine 177.9 in model 205, 253 | GF07.70-P-9998MNA | |
| Engine 177.9 in model 213 up to model year 2021 | GF07.70-P-9998MNE |