Smooth Running Control, Function - GF07.10-P-1011KJ

ENGINE 281.910 in MODEL 453.0/3/4 

Function requirements for smooth running control, general points 

• Circuit 87 (Engine management ON)
• Engine runs

Function sequence for smooth running control, general points 

Engine running is constantly monitored in order to protect the catalytic converter from thermal overload if combustion misfiring occurs.

For smooth running control, the ME-SFI [ME] control unit (N3/10) reads in the following signals:

• Intake camshaft Hall sensor (B6/15), intake camshaft setting
• Coolant temperature sensor (B11/4)
• Pressure sensor downstream of throttle valve (B28/7), engine load
• Crankshaft position sensor (L5), engine speed
• Electronic Stability Program control unit (N30/4), wheel speed signal via the interior CAN (CAN B)

Function sequence for smooth running control 

The function sequence is described in the following steps:

• 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 position sensor is evaluated using a comprehensive mathematical procedure, to check for precise uniformity of timing between individual combustions. Each individual combustion must generate a characteristic acceleration at the sensor rotor. 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 misfiring, the corresponding cylinder 1 injection valve (Y62/1) to cylinder 3 injection valve (Y62/3) is no longer actuated after a certain number of combustion misfires.

For combustion misfire recognition the time period of 5 incremental wheel teeth is measured after TDC for every cylinder (the time the 5 teeth need to pass by the crankshaft position sensor) and stored. This function is active for rotational speeds between 300 and 5000 rpm. To recognize the stored values are taken as a reference. In doing so catalytic converter-damaging (size) as well as polluting (small) combustion misfires recognized as per the requests of the European OBD (EOBD).

Smooth running signal 

Courtesy of MERCEDES-BENZ USA

What is detected is combustion misfiring caused by:

• Ignition system
• Fuel injection system
• Mechanical engine components (for example, 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 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. The ME-SFI [ME] control unit receives the wheel speed signal (for detection of uniform wheel rotation) from the Electronic Stability Program control unit via the interior CAN.

Synchronization of injection and firing order 

Cylinder detection using the signals from the crankshaft position sensor and intake camshaft Hall sensor is required for fault storage and assessment.

Sensor adaptation 

The tolerance range for smooth running control is reduced after successful adaptation of the crankshaft position 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 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.

	Electrical function schematic for smooth running control		PE07.10-P-2711-97BBA
	Overview of system components motor electronics (ME-SFI) fuel injection and ignition system		GF07.61-P-9997KJ