GF07.61-P-3033MMI Cylinder Shutoff Function
GF07.61-P-3033MMI Cylinder Shutoff Function
ENGINES 152.9 in MODEL 172.4
Function requirements for CSO, general points
^ Circuit 87M (engine timing ON)
^ Engine running
CSO, general points
The CSO has the task to reduce the fuel consumption in partial load operation through cutting out of cylinder 2, 3, 5, 8. The shutoff takes place characteristic map dependent by the ME-SFI [ME] control unit (N3/10).
A consumption reduction takes place through:
- Increase in the effectiveness by means of operating point shifting of further driven cylinder at higher loads
- Reduction of the gas cycle losses through closing of the valves of the switched off cylinder
The ME-SFI [ME] control unit reads in the following sensors and signals for CSO:
- Coolant temperature sensor (B11/4)
- Pressure sensor downstream of throttle valve (B28/7), engine load
- LH and RH intake camshaft Hall sensors (B6/4, B6/5), intake camshaft positions
- LH and RH exhaust camshaft Hall sensors (B6/6, B6/7), exhaust camshaft positions
- Oil sensor (oil level, temperature and quality) (B40) via the drivetrain LIN (LIN C1)
- Crankshaft Hall sensor (B70), engine speed
- Actual value potentiometer 1 and 2 (M16/6r1, M16/6r2), throttle valve position
- Electronic Stability Program control unit (N30/4) wheel speed via the chassis CAN (CAN E)
- Fully integrated transmission control unit (Y3/8n4), gear range via the drive train CAN (CAN C)
The following measures are taken for CSO:
- Cutting out of the fuel injectors (Y76)
- Cutting out of the ignition coils (T1)
- Closing off of the intake valves through actuation of the left and right inlet side CSO valve (Y80/1, Y80/2)
- Closing off of the exhaust valves through actuation of the left and right exhaust side CSO valve (Y80/3, Y80/4)
Presentation: firing order for engine 152
A Right cylinder head
B Left cylinder head
C Cylinder which be switched off
D Firing order
E Direction of travel
Function sequence for CSO
The CSO is described in the following points:
^ CSO switching conditions
^ Function sequence for CSO On
^ Function sequence for CSO Off
^ Function sequence for combustion compartment ventilation
^ Function sequence for set up of gas-operated spring
^ Function sequence for exhaust flaps
CSO switching conditions
The conditions for switching on or switching off the CSO are described in the following points:
^ Cylinder shutoff activation conditions
^ Cylinder shutoff deactivation conditions
Cylinder shutoff activation conditions
^ Transmission mode C and ECO activated
^ Blocking time after engine start elapsed (approx. 10 s at 90°C coolant temperature or approx. 75 s at +20°C).
^ Coolant temperature between 20°C and 110°C
^ Engine oil temperature between 20°C and 130°C
^ Lowest engine rpm:
1st - 2nd gear: n greater than 1100 rpm
3rd gear: n greater than 900 rpm
4th - 7th gear: n greater than 800 rpm
^ Lowest speed:
v greater than 20 km/h for a closed soft top
v greater than 60 km/h for an open soft top
^ System diagnosis complete and system fault-free
^ no mixture adaptation
Cylinder shutoff deactivation conditions
^ Ignition misfires with are "damaging to the catalytic converter" recognized
^ Cylinder shutoff fault detected
^ Electronic accelerator limp-home mode
^ Fault in oil temperature signal
^ Excessive irregular engine running when cylinder shutoff ON
^ maximum permissible, uninterrupted operating time of approx. 800 seconds exceeded.
Sectional view of cylinder
1 Intake camshaft
2 Intake port
3 Switchable supports
4 Exhaust camshaft
5 Exhaust port
Function sequence for CSO On
If the CSO is releases, the ME-MFI [ME] control unit actuates the LH and RH intake CSO valves (Y80/1, Y80/2) and the LH and RH exhaust CSO valves (Y80/3, Y80/4). Though this the hydraulically switchable supports have hydraulic pressure applied to them from the auxiliary oil pump. In this way two blocking pieces are pressed into the support and the upper part of the support is pushed through the cam working from above against the spring force into the guide.
The valve cam follower is decoupled by this from the camshaft and the valve remains closed by the spring force of the valve spring.
This occurs simultaneously with the intake and exhaust valves for cylinders 2, 3, 5 and 8.
Presentation of CSO On
1 Support
2 Integrated spring support
3 Blocking pieces
4 Valve
5 Valve spring
6 Valve cam follower
Function sequence for CSO Off
For deactivation of the CSO the LH and RH intake side CSO valves and the LH and RH exhaust side CSO valves are no longer actuated. Thus the hydraulically switchable supports no longer have hydraulic pressure applied to them and they can expand until the blocking pieces engage due to the integrated spring.
The valve cam follower is again pressed by this against the cam and the power transmission is again created from the cam to the cam follower.
Shown: CSO off
1 Support
2 Integrated spring support
3 Blocking pieces
4 Valve
5 Valve spring
6 Valve cam follower
Function sequence for combustion compartment ventilation
In the time period for CSO deposits of condensed exhaust (sooting) can occur on the spark plugs and walls of the combustion chamber in a switched of cylinder. This can be prevented if the intake valves are opened and the included air renewed in certain intervals dependent on intake manifold pressure and the engine rpm.
Function sequence for set up of gas-operated spring
In order to improve the neutrality of torques and to reduce the load on components fresh air is included during the CSO in each switched off cylinder in the form of a gas-operated spring. To do this the intake valves are opened for a short time if the piston has reached BDC.
Function sequence for exhaust flaps
The exhaust flaps serve to optimize the exhaust smoke behavior. They are mostly closed in ranges involving low engine loads. The exhaust flaps begin to open and are fully open at wide open throttle from the central load range. In this way an exhaust system can be acoustically combined for the 4 and 8 cylinder operation. The exhaust flaps are actuated load-dependent and according to a characteristics map for the respective transmission mode.
