Cylinder Shutoff, Function

Cylinder Shutoff, Function

ENGINE 137.970

1 Shift oscillating lever, exhaust side (locked)
1a Roller lever
1b Valve lever
1c Compression spring
1d Coupling pin
1e Pressure pin
2 Shift oscillating lever, inlet side (locked)
2a Roller lever
2b Valve lever
2c Compression spring
2d Coupling pin
2e Pressure pin
3 Oscillating lever shaft
21 Exhaust flap
22 Vacuum reservoir
23 Secondary oil pump
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 Cylinder shutoff oil pressure sensor
L5 Crankshaft position sensor
M16/6 Throttle valve actuator
N3/10 ME-SFI [ME] control module
N92/2 ECI ignition module left cylinder bank
Y62 Fuel injectors for Cylinders 7 - 12
Y80/1 Cylinder shutoff valve cylinders 7 - 9
Y81/1 Cylinder shutoff valve cylinders 10 - 12
Y93 Exhaust flap switchover valve
X11/4 Diagnostic data link connector
a Vacuum supply
CAN databus (Controller Area Network)

Design/function
The left bank of cylinders is shut off by no longer operating its inlet and exhaust valves. The valves remain constantly closed during cylinder shutoff.
At the same time fuel injection is interrupted and the spark duration of the left bank of cylinders is greatly shortened.

The cylinder shutoff function is integrated in the ME control module. The following inputs and outputs/functions are required:
- Actuation of cylinder shutoff valve cylinders 7 - 9 (Y80/1)
- Actuation of cylinder shutoff valve cylinders 10 - 12 (Y81/1)
- Actuation of exhaust flap switchover valve (Y93)
- Signal of cylinder shutoff 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, for example:
- 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:
- Deactivating fuel injection for the cylinders shut off, greatly shortening the spark duration of the left bank of cylinders, further maps for injection time and ignition timing point when cylinder shutoff ON
- Actuation of throttle valve actuator
- Recognition of combustion misfiring by means of ionic current signals
- 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 oscillating levers are interlocked by means of moving coupling pins when cylinder shutoff OFF. Springs push the coupling pins into the "interlocked" position.

1 Shift oscillating lever exhaust side
1a Roller lever
1b Valve lever
1c Compression spring
1d Coupling pin
1e Pressure pin
2 Shift oscillating lever inlet side
2a Roller lever
2b Valve lever
2c Compression spring
2d Coupling pin
2e Pressure pin
3 Oscillating lever shafts

When cylinder shutoff ON the decoupled valve levers are supported on the base circle of the cylinder shutoff on the camshaft. The roller levers are pushed further along their camshaft track by spring elements. This ensures that both valve and roller levers maintain a defined position and the coupling pin is able to slide again into the hole in the roller lever when cylinder shutoff OFF.

1a Roller lever, exhaust side
1b Valve lever, exhaust side
2a Roller lever, inlet side
2b Valve lever, inlet side
3a Oscillating lever shaft, lubricating oil
3b Oscillating lever shaft, pressurized oil when cylinder shutoff ON
4 Camshaft
4a Base circle of cylinder shutoff on camshaft
5 Spring element

Pressurized oil supply
The secondary oil pump is positioned ahead of the left bank of cylinders to provide a reliable supply of pressurized oil for the cylinder shutoff. The oil pressure in the idle speed range is already greater than 3 bar. The pump is driven by the camshaft.

5/1 Camshaft adjustment, left bank of cylinders
23 Secondary oil pump
a Inlet side (engine oil pressure)
b Pressure side
c Feed from cylinder head (engine oil pressure)
d Pressurized oil for camshaft adjustment (engine oil pressure)
e Pressurized oil for cylinder shutoff (secondary oil pump pressure)
23/1 Pump drive
23/2 Internal rotor
23/3 External rotor
B40/2 Cylinder shutoff oil pressure sensor
Y49/1 Camshaft adjustment valve left cylinder bank

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 oscillating levers 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.
- Cylinder shutoff commences at cylinder 7 or at cylinder 12.

Cylinder shutoff activation conditions
- Blocking time after engine start elapsed (approx. 10 s at 90 °C coolant temperature or approx. 75 s at +20 °C).
- Coolant temperature greater than approx. +20 °C.
- It is necessary to shift into 3rd gear or higher in order to activate the cylinder shutoff. After this, the cylinder shutoff is activated in all gear positions from approx. 650 - 3000 rpm.
- Throttle valve angle less than speed-related threshold.
- Engine oil pressure greater than approx. 3 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
- Electronic accelerator emergency mode
- Fault in oil temperature signal
- Fault in oil pressure signal
- Request from function chain test
- Maximum permissible, uninterrupted operating time of approx. 4 min exceeded.
After about 30 s without cylinder shutoff, the cylinder shutoff is again enabled.
- Secondary air injection diagnosis active

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.

Correction programming of cylinder shutoff
The following settings are possible:
- Stage 0: Engagement threshold from basic map (basic setting)
- Stage 1: Cylinder shutoff below 2000 rpm enlarged
- Stage 2: Cylinder shutoff restricted below 2000 rpm
- Stage 3: Cylinder shutoff disabled

Note: Correction programming of the cylinder shutoff is permissible only for a temporary period when dealing with complaints.
In stage 1 the cylinder shutoff engages more frequently below 2000 rpm. Depending on the style of driving slight improvements in the fuel consumption are possible, but restrictions in comfort (humming noises) are likely.
Stage 2 or 3: A restriction or blocking of the cylinder shutoff must only be performed for a temporary period if major complaints regarding comfort exist and at the same time involves drawbacks in terms of fuel consumption.

Actuation of throttle valve actuator
When cylinder shutoff ON 6 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. 2200 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 of the exhaust system.

Actuation of the cylinder shutoff valves
The electromagnetic cylinder shutoff valves (Y80/1, Y81/1) 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