Smooth running control, function - GF07.10-P-1011MMW
ENGINE 276.9 in MODEL 212.095 as of model year 2014
Function requirements for smooth running control, general points
- Circuit 87M (engine timing ON)
- Engine running
The function requirements "internal combustion engine running" includes all function sequences of the fuel low pressure and high-pressure circuit, as described in the function "fuel supply".
Smooth running control, general points
Engine running is constantly monitored in order to protect the catalytic converters from excessive thermal overloading if combustion misfirings occur.
The ME-SFI [ME] control unit (N3/10) reads in the following sensors and signal for smooth running control:
- 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
- Coolant temperature sensor (B11/4)
- Pressure sensor downstream of throttle valve (B28/7), engine load
- Crankshaft Hall sensor (B70), engine speed
- Regenerative braking system control unit (N30/6), wheel speed signal via chassis CAN 2 (CAN E2)
Function sequence for smooth running control
The function sequence is described in the following steps:
- Function sequence for combustion misfire detection
- Function sequence for misfire counter
- 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 increment wheel (perforated plate). If there are combustion misfires, the increment wheel turns slightly more slowly until the next ignition (due to torque fluctuation). If the smooth running control in the ME-SFI [ME] control unit detects combustion misfiring, the corresponding fuel injector (Y76) is no longer actuated after a certain number of combustion misfires. However at least two fuel injectors are deactivated simultaneously.
Function sequence for misfire counter
The total number of combustion misfires detected is stored in the fault memory and subdivided into:
- "Cylinder-specific" combustion misfires
- "Emission limit" combustion misfires
- "Catalytic converter damaging" combustion misfires
What is detected is combustion misfiring caused by:
- Ignition system - injection system - mechanical engine components (e.g. valve seats, valve springs, unmetered air - fuel starvation
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 fuel injection and firing order
- Sensor adaptation
Engine speed and engine load
Using the engine speed and engine load, the ME-SFI [ME] control unit computes 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 engine running at certain engine speeds and load conditions. Therefore, the tolerance range for smooth running control is increased on poor road surfaces ("wash board").
The ME-SFI control [ME] unit receives the wheel speed signal (for detection of even wheel rotation) via the chassis CAN 2 from the regenerative braking system control unit.
Synchronization of fuel injection and firing order
Cylinder identification is required for fault storage and assessment, using the signals from the crankshaft Hall sensor and the intake camshaft Hall sensors or 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 stores the smooth operation characteristics of the engine during a deceleration phase (accelerator pedal not operated) when uniform smooth operation is present. These are required as a comparison parameter for misfire detection.
Smooth engine running signal
| Electrical function schematic for smooth running control | PE07.10-P-2711-97DAU | ||
| Overview of system components for gasoline injection and ignition system with direct injection | GF07.70-P-9998MMO |