Smooth Running Control, Function - GF07.10-S-1011TRJ
Engine 274 in model 447.6/7
with code XM0 (Facelift)
Function requirements for smooth running control, general points
- Circuit 87M ON (Engine management ON)
- Engine running.
Smooth running control, general points
Engine running is constantly monitored in order to protect the catalytic converter from thermal overload if combustion misfiring occurs.
The ME-SFI [ME] control unit (N3/34) needs the following sensors and signal for smooth running control:
- Intake camshaft Hall sensor (B6/29)
- Exhaust camshaft Hall sensor (B6/30)
- Coolant temperature sensor (B11/21)
- Intake manifold pressure sensor (B28/24)
- Crankshaft Hall sensor (B70/2)
- Electronic Stability Program (ESP) control unit (N30/4) for wheel speed
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 position 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 multiple wheel which is located on the crankshaft. If there are combustion misfires, the multiple 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 (Y62) is no longer actuated after a certain number of combustion misfires. However at least two fuel injectors are deactivated simultaneously.
Smooth running signal
Function sequence for misfire counter
The total for the detected combustion failures is entered in the fault memory. A differentiation is made in this connection between the following combustion failures:
- "Cylinder-specific"
- "Emission limit"
- "Catalyst degrading"
What is detected is combustion misfiring caused by:
- Ignition system
- Mechanical engine components (for example, valve seats, valve springs, unmetered air)
- Fuel injection system
- Fuel deficiency
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 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 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.
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.
In the overrun mode (accelerator pedal not actuated) in which a uniform smooth operation is present, the ME-SFI [ME] control unit stores the smooth engine operation characteristics. These are required as a comparison parameter for the detection of combustion failures.
| Function schematic for smooth running control | PE07.10-S-2502-97TRM | ||
| Overview of system components for gasoline injection and ignition system with direct injection | GF07.70-S-9998TRJ |