Smooth Running Control, Function - GF07.10-P-1011MNF
Engine 176.9 in model 463
as of model year 2016 up to model year 2019
Function requirements for smooth running control, general points
- Circuit 87M (Engine management ON)
- Engine runs
The circuit relay 87M(F58kN) is switched on for circuit 15 ON.
Smooth running control, general points
Smooth running control ensures that the engine is also smooth in fuel saving lean-burn operation in partial-load range and turns evenly. In this way the tangible rough running should be avoided for the driver. Also the CATs are protected from thermal overloading if there are combustion misfires.
For smooth running control, the ME-SFI [ME] control unit (N3/10) reads in signals from the following sensors:
- Left intake camshaft Hall sensor (B6/4) and right intake camshaft Hall sensor (B6/5), intake camshaft positions
- Left exhaust camshaft Hall sensor (B6/6) and right exhaust camshaft Hall sensor (B6/7), exhaust camshaft positions
- Coolant temperature sensor (B11/4), coolant temperature
- Pressure sensor downstream of left throttle valve (B28/22) and pressure sensor downstream of right throttle valve (B28/23), engine load
- Crankshaft Hall sensor (B70), engine rpm
- Wheel speed signals
The Electronic Stability Program control unit (N30/4) sends the wheel speed signals via chassis CAN 1 (CAN E1), powertrain control unit (N127), and Drivetrain CAN (CAN C) to the ME-SFI [ME] control unit.
Function sequence for smooth running control
The smooth running control function includes the following subfunctions:
- Function sequence for combustion misfire detection
- Function sequence for factors for smooth running control
Function sequence for combustion misfire detection
For the smooth running control, the signal from the crankshaft Hall sensor is evaluated using a comprehensive mathematical procedure, to check for precise uniformity of timing between individual combustions. Each individual combustion must produce a characteristic acceleration at the sensor rotor (perforated plate). If there are combustion misfires, the sensor rotor turns up to the next ignition somewhat slower (torque fluctuation).
If the smooth running control in the ME-SFI [ME] control unit detects combustion failures, the corresponding fuel injectors for cylinders 1 up to 8 (Y76/1 up to Y76/8) are no longer actuated after a certain number of combustion misfires. However only a maximum of three fuel injectors are deactivated simultaneously.
The total number of combustion misfires detected is stored in the ME-SFI [ME] control unit fault memory and subdivided into:
- "cylinder-specific" combustion misfires
- "emission limit" combustion misfires
- "catalytic converter damaging" combustion misfires
Combustion misfire can be caused by:
- Ignition system
- Fuel injection system
- Mechanical engine components (for example, valve seats, valve springs, unmetered air)
- Fuel deficiency
Smooth running signal
Function sequence for factors for smooth running control
The following factors affect smooth running control:
- Engine speed and engine load
- Coolant temperature
- Recognition of road bumps
- Synchronization of injection and firing order
- Sensor adaptation
Engine speed and engine load:
Using the engine speed and engine load, the ME-SFI [ME] control unit calculates a reference value for the time between two combustions.
Coolant temperature:
For a cold engine more combustion misfires are permissible than for an engine at operating temperature.
Recognition of road bumps:
Vibrations transmitted through the Drivetrain may have a negative effect on evaluation of the engine running at certain engine speeds and load conditions. Therefore, the tolerance range for smooth running control is increased on poor road surfaces.
The Electronic Stability Program control unit sends the wheel speed signals (for detection of uniform wheel rotation) to the ME-SFI [ME] control unit via chassis CAN 1.
Synchronization of injection and firing order:
Cylinder detection is required for fault storage and evaluation using the signals from the crankshaft Hall sensor and the intake camshaft Hall sensors or the exhaust camshaft Hall sensors.
Sensor adaptation:
The tolerance range for smooth running control is reduced after successful adaptation of the crankshaft Hall sensor.
In this way, the smooth running control can be adapted to the specific smooth running characteristics of the engine.
The ME-SFI [ME] control unit saves the smooth engine operation characteristics in overrun mode (accelerator pedal not actuated) where uniform smooth operation is present. These are required as a comparison parameter for misfire detection.
| Electrical function schematic for smooth running control | PE07.10-P-2711-97ZGD | ||
| Overview of system components for gasoline injection and ignition system with direct injection | GF07.70-P-9998MNF |