Cylinder Shutoff, Function

Cylinder Shutoff, Function

ENGINE 113.960 with CODE (479) Cylinder shutoff




1 - 8 Cylinders 1 to 8 - Cylinder shutoff at cylinders 2 ,3, 5 and 8
1 Shift rocker arm (locked)
1a Roller lever
1b Valve lever
1c Spring
1d Coupling pin
1e Pressure pin
21 Exhaust flap
B2/5 Hot film MAF sensor
B11/4 Coolant temperature sensor
B28 Pressure sensor (intake manifold)
B40 Oil sensor (oil level/temperature/quality)
B40/2 Oil pressure sensor
Y62 Fuel injectors for cylinders 2 ,3, 5 and 8
Y80 Cylinder shutoff valve, right bank of cylinders
Y81 Cylinder shutoff valve, left bank of cylinders
Y93 Exhaust flap switchover valve
L5 Crankshaft position sensor
M16/6 Throttle valve actuator
N3/10 ME-SFI [ME] control module
T1/2 Ignition coil for cylinder 2
T1/3 Ignition coil for cylinder 3
T1/5 Ignition coil for cylinder 5
T1/8 Ignition coil for cylinder 8
X11/4 Diagnostic data link connector
a to vacuum reservoir
CAN databus (Controller Area Network)

Task
Reducing fuel consumption.
To achieve this, cylinders 2 and 3 of the right bank of cylinders as well as cylinders 5 and 8 of the left bank of cylinders are shut off in certain operating states of the engine.

Design/function
Cylinders 2 and 3 (right bank of cylinders) as well as cylinders 5 and 8 (left bank of cylinders) are shut off by no longer operating their inlet and exhaust valves. The valves remain constantly closed during cylinder shutoff.
At the same time the fuel injection and ignition are interrupted.

The cylinder shutoff function is integrated in the ME control module. The following inputs and outputs/functions are required:
- Actuation of cylinder shutoff valve, right bank of cylinders (Y80)
- Actuation of cylinder shutoff valve, left bank of cylinders (Y81)
- Actuation of exhaust flap switchover valve (Y93)
- Signal from oil pressure sensor (B40/2)
- Signal from pressure sensor (B28), intake manifold pressure
- Fault detection of cylinder shutoff

Input signals already present are also used in the ME control module for the cylinder shutoff. These are:
- Crankshaft position and engine speed
- Engine load
- Throttle valve position
- Engaged gear
- Oil temperature

Existing functions in the ME control module are harmonized to the cylinder shutoff. For example:
- Interrupting fuel injection and ignition for the cylinders that are shut off, further maps for injection time and ignition timing point when cylinder shutoff ON
- Actuation of throttle valve actuator
- Smooth engine running analysis, further maps for cylinder shutoff ON/OFF
- Engine load calculation, takes into account various air masses
- Mixture adaptation, for various air masses and pressure ratios
- Correction programming with STAR DIAGNOSIS

Cylinder shutoff OFF
Both parts of the shift rocker arms are interlocked by the moving coupling pin when cylinder shutoff OFF. A spring pushes the coupling pin into the "interlocked" position.




1 Shift rocker arm
1a Roller lever
1b Valve lever
1c Spring
1d Coupling pin
1e Pressure pin
3 Rocker arm shafts
4 Camshaft

Cylinder shutoff ON
The electromagnetic cylinder shutoff valves (Y80, Y81) are actuated by the ME control module and open. Pressurized oil flows through the rocker arm shafts behind the pressure pins and the coupling pins are pushed back. Both parts of the rocker arm are now able to move freely relative to each other - inlet and exhaust valves are no longer operated.
The decoupled valve lever is supported on the base circle on the camshaft. This ensures that the coupling pin is again able to slide into the hole in the roller lever when cylinder shutoff OFF.




1 Shift rocker arm
1a Roller lever
1b Valve lever
1c Spring
1d Coupling pin
1e Pressure pin
3 Rocker arm shafts
4 Camshaft

Shift point cylinder shutoff
If the shift conditions are met, the cylinder shutoff can be switched on only in certain engine positions in view of the mechanical circumstances at the engine:
- The engine valves must be closed. Shifting is only possible when the rocker arms are relieved.
- Following a power stroke, it is always the exhaust valves which are switched off first, then the inlet valves.
This ensures that pressurized exhaust gas is enclosed in the cylinder which is shut off. The overpressure prevents oil being drawn out of the crankcase. The lambda control remains unaffected once the cylinder subsequently operates once again and the exhaust gas escapes.
- At the right bank of cylinders it is first of all cylinder 2 which is switched off followed by cylinder 3, and at the left bank of cylinders first of all cylinder 8, then cylinder 5.

Cylinder shutoff activation conditions
- Blocking time (approx. 20 s) after engine start elapsed
- Coolant temperature greater than approx. +20 °C
- Engine speeds when engine at operating temperature
approx. 925 rpm up to 1700 rpm in engaged 3rd gear
approx. 925 rpm up to 1700 rpm in engaged 4th gear
approx. 925 rpm up to 3500 rpm in engaged 5th gear
- Driving stage 3, 4 or D
- Throttle valve angle less than speed-related threshold
- Engine oil pressure greater than approx. 2.5 bar
- Engine oil temperature between approx. 20 °C up to 130 °C
- Intake air temperature approx. - 40 °C up to 100 °C
- Altitude less than approx. 2500 m above NSL
- Battery voltage higher than approx. 10.5 V
- Cylinder shutoff enabled when conducting variant coding with STAR DIAGNOSIS
- ASR control not active

Cylinder shutoff deactivation conditions
- Misfiring "damaging TWC" detected
- Cylinder shutoff fault detected
- Emergency mode of electronic accelerator pedal
- Fault in oil temperature signal
- Fault in oil pressure signal
- Request from function chain test
- Excessive irregular engine running when cylinder shutoff ON
- Maximum permissible, uninterrupted operating time of approx. 25 min exceeded.
After about 20 s without cylinder shutoff, the cylinder shutoff is again enabled.

Cylinder shutoff engagement threshold
The engagement threshold determines how the cylinder shutoff switches on and off in the moderate engine speed and load range.
It is dependent on the correction programming with the STAR DIAGNOSIS.
The following settings of the correction programmming are possible:
- Engagement threshold from basic map (basic setting)
- Cylinder shutoff restricted below 1500 rpm
- Cylinder shutoff restricted in entire map
- Cylinder shutoff disabled

Note: Correction programming with the STAR DIAGNOSIS is only permissible for a temporary period if major complaints regarding comfort exist.
Restricting the cylinder shutoff at the same time involves drawbacks in terms of fuel consumption.

Actuation of throttle valve actuator
When cylinder shutoff ON 4 cylinders of the engine are shut off. The throttle valve is opened further in line with the engine load and speed to ensure that the engine torque remains as constant as possible.
When cylinder shutoff OFF the situation is reversed and the throttle valve is closed accordingly.
Operation of the throttle valve is performed shortly before cylinder shutoff ON or OFF.
The same engine torque should, if possible, be available when switching over between the two engine operating modes to ensure that the driver does not sense any difference in power output and the switchover takes place smoothly.

Actuation of the exhaust flap
When cylinder shutoff ON the electromagnetic exhaust flap switchover valve is actuated by the ME control module up to approx. 2500 rpm. Vacuum flows into the aneroid capsule and the exhaust flap partially shuts off the cross-section of the exhaust pipe. This makes it possible to optimize the noise characteristic.

Actuation of the cylinder shutoff valves
The electromagnetic cylinder shutoff valves (Y80, Y81) are actuated by the output stages in the ME control unit by means of a pulsed d.c. voltage.

When the cylinder shutoff is switched on, the on/off ratio is set to approx. 95 % for not more than 0.5 s in order to increase the starting current and to achieve a more rapid response. The time limit also protects the coil windings from excessive thermal stresses.

Further measures at engine/transmission in connection with cylinder shutoff
- Compound oil pump (operating principle same as engine 120) with high delivery
- Vibration damper at belt drive
- Torque converter with turbine torsion damper for optimized noise characteristic