Cylinder Shutoff, Function - GF07.61-P-3033MNL

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 CSO, general points 

• Circuit 87M (Engine management ON)
• Engine runs

CSO, general points 

The CSO has the task of reducing the fuel consumption in partial load operation by shutting off cylinders 2, 3, 5 and 8. The shutoff is carried out by the ME control unit (N3/10) depending on the characteristics map.

The following effects of cylinder shutoff reduce the fuel consumption:

• 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

For cylinder shutoff, the ME control unit reads in the following signals:

• Coolant temperature sensor (B11/4), coolant temperature
• Left and right pressure sensors downstream throttle valve (B28/22, B28/23), engine load
• Left and right intake camshaft hall sensors (B6/4, B6/5), intake camshaft positions
• Left and right exhaust camshaft hall sensors (B6/6, B6/7), exhaust camshaft positions
• Crankshaft Hall sensor (B70), engine speed
• Left and right actual value potentiometer 1 and 2 (M16/60r1, M16/60r2, M16/61r1, M16/61r2), throttle valve position
• Electronic Stability Program control unit (N30/4), wheel speed via the suspension FlexRay (Flex E)
• Fully integrated transmission control unit (Y3/8n4) (model 217, 222), drive range via drive CAN (CAN C1)
• Fully integrated transmission control electric controller unit control unit (Y3/8n4) (for model 290), drive range via drive CAN (CAN C1)

The following measures are taken to shut the cylinder off:

• Fuel injector cylinders 2, 3, 5 and 8 (Y76/2, Y76/3, Y76/5 and Y76/8) are shut off
• Ignition coil cylinders 2, 3, 5 and 8 (T4t2, T4/1t3, T4/2t5 and T4/3t8) are shut off
• Intake valves are closed by actuating the intake CAMTRONIC actuators for cylinders 2, 3, 5 and 8 (Y49/11, Y49/13, Y49/15, Y49/17)
• Exhaust valves are closed by actuating the exhaust CAMTRONIC actuators for cylinders 2, 3, 5 and 8 (Y49/12, Y49/14, Y49/16, Y49/18)

Diagram of CSO and firing order 

Courtesy of MERCEDES-BENZ USA

Function sequence for CSO 

The CSO is described in the following points:

• CSO switching conditions 
• Function sequence for cylinder shutoff 
• Function sequence for combustion compartment ventilation 
• Function sequence for set up of gas-filled springs 

CSO switching conditions 

Cylinder shutoff activation conditions 

• Drive programs "C" and "ECO on" are activated
• Coolant temperature between 30 and 110°C
• Vehicle speed between 20 km/h and 140 km/h
• Motor speed between 1000 rpm and 3250 rpm
• Control unit temperature up to a maximum of 105°C
• System diagnosis complete and system fault-free
• no mixture adaptation

Cylinder shutoff deactivation conditions 

• Ignition misfires that are "damaging to the catalytic converter" recognized
• Cylinder shutoff error detected
• Electronic accelerator limp-home mode
• Excessive irregular engine running with cylinder shutoff
• Maximum permissible, uninterrupted operating time of approx. 600 s exceeded

Function sequence for cylinder shutoff 

Switch off intake and exhaust valves for cylinders 2, 3, 5 and 8. Switch fuel injectors and ignition coils off.

The CAMTRONIC actuators are actuated by the ME control unit with a pulse width modulated signal. In doing so, a coil is energized in the corresponding actuator and a tappet moves into a corresponding curved track on the cam sleeve. Due to the turning of the camshaft and the design of the curved track, the cam sleeve is shifted axially on the camshaft. The roller-type cam follower is decoupled from the camshaft by the axial shifting and the valve remains closed due to the spring force of the valve spring.

A bump in the curved track has the effect of bringing the tappet back to the default position. To reset the cam sleeve, a second tappet moves into the relevant curved track and the reset occurs accordingly.

The position of the tappets is determined using an integrated Hall sensor.

Sectional view of cylinder head cover in the left cylinder bank 

Courtesy of MERCEDES-BENZ USA

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 valves are opened and the trapped air is replaced in certain intervals, depending on engine load and speed.

Function sequence for set up of gas-filled springs 

In order to improve the neutrality of torques and to reduce the load on components, fresh air is introduced into each shut-off cylinder during the cylinder shutoff via a pneumatic spring. To do this the intake valves are opened for a short time if the piston has reached BDC.

	Electrical function schematic for CSO	Engine 177.9 in model 290 up to model year 2021	PE07.61-P-2794-97XBA
		Engine 176.9, 177.9 in model 217Engine 176.9, 177.9 in model 222	PE07.61-P-2794-97SEL
	Overview of system components for gasoline injection and ignition system with direct injection		GF07.70-P-9998MNL