S07.10-0012-79
Block diagram |
A1/1 | Instrument cluster (KI) control unit | N3/34 | ME-SFI [ME] control unit | |
A16 | Knock sensor | N45 | Transfer case (VG) control unit | |
B2/8 | Hot film mass air flow sensor | N93 | Central gateway (CGW) | |
B6/15 | Intake camshaft position sensor | CAN HMI | User interface CAN | |
B6/16 | Exhaust camshaft position sensor | CAN V | Vehicle CAN | |
B11/17 | Coolant temperature sensor | A | Mercedes-Benz | |
B37/4 | Accelerator pedal module | B | Nissan | |
B70/2 | Crankshaft Hall sensor | C | Default | |
B79/2 | Transmission neutral position position sensor | D | Optional | |
M16/6 | Throttle valve actuator |
Function requirements for knock control, general points
Circuit 87 ON (engine management ON)
Engine running.
Knock control, general points
Knock control is integrated into the ME-SFI control unit and has the task for different fuel grades and for all operating conditions to ensure knock-free operation of the engine. In case of uncontrolled combustion (knocking), the ignition timing of the ignition coils of the relevant cylinder is retarded.
The ME-SFI control unit manages the knock control according to the following sensors and signals:
Knock sensor, knocking signal
Intake camshaft position sensor, intake camshaft position (ignition circuit detection)
Exhaust camshaft position sensor, exhaust camshaft position (ignition circuit detection)
Coolant temperature sensor, coolant temperature
Accelerator pedal module, accelerator pedal position
Hot film mass air flow sensor
Throttle valve actuator
Transmission neutral position position sensor
Instrument cluster (KI) control unit
Crankshaft Hall sensor, engine speed and crankshaft position, ignition circuit detection
The requirements of the torque coordination function are also taken into account.
Function sequence for knock control
RON = research octane number
The function sequence is described in the following steps:
Function sequence for ignition angle setting
Function sequence for RON regulation
Function sequence for knock control adaptation
Function sequence for knock identification error
Function sequence for ignition angle setting
According to its input signals, the ME-SFI control unit computes the cylinder-specific ignition angle setting.
If the knock sensor detects knocking at a cylinder, its timing (regardless of the engine speed) is retarded from the next ignition. If knocking persists, the timing is retarded for as long as is necessary until the maximum retard position is reached.
If knocking-free combustion exists, retarding of the ignition timing is reduced in stages after a few ignitions (depending on engine speed) until the normal characteristics map value is achieved or knocking once again occurs.
Function sequence for RON regulation
Knock control is also fitted out with an automatic RON switch. This detects a persistent high tendency to knock of the engine and assists the knock control by means of an appropriate pre-control.
This is done by evaluating the stored adaptation values, the ignition angle of all the cylinders and the number of control interventions in certain engine load and speed ranges.
The RON stage is adjusted in one or several stages depending on the threshold which has been exceeded. The regulated RON stage remains until stopping of the engine.
The higher the selected RON stage, the smaller the maximum retard position of the ignition timing.
Function sequence for knock control adaptation
Adaptation by the knock control becomes active starting from a high coolant temperature.
The ignition angle corrections required due to combustion knocking are stored continuously for the specific cylinder, along with the related operating condition of the engine (engine load and engine speed).
When determining the individual ignition angles, the stored adaptation values are taken into account, so that the optimal ignition angle can be calculated immediately for each cylinder.
Function sequence for knock identification error
Upon failure of the knock sensor signal, the ignition timings of all cylinders (depending on engine speed and coolant temperature) are retarded. Knock control and the adaptation are deactivated and a fault is stored in the fault memory.
The ignition angle corrections of the thermal management and the knock control are added based on the performance map.