GF07.61-P-3008KE Motor Electronics (ME) Ignition System, Function

GF07.61-P-3008KE Motor Electronics (ME) Ignition System, Function
- up to model year 08

Component Identification:

The high voltage is distributed rotorlessly. Advantages of the rotorless high voltage distribution are:
^ Essentially lower electromagnetic base noise
^ No rotating parts (noise/wear reduction)
^ Fewer high voltage connections

1. Determining the ignition angle in line with the input signals and actuating the ignition coils
The ME-SFI control unit essentially analyzes the following signals for determining the ignition angle:
^ Hot film mass air flow sensor,
^ Crankshaft position sensor,
^ Intake/exhaust camshaft Hall sensor,
^ Coolant temperature sensor,
^ Intake air temperature sensor,
^ Knock sensor,
^ Pressure sensor (intake manifold),
^ Torque request via CAN
and interrupts at the ground end the ignition coil ignition coil primary circuit in the very ignition timing moment.

2. Ignition angle adaptation
2.1 START
When the engine is started and up to approx. 500 rpm, the ignition timing is controlled by means of a specific start map. At the same time only the signals from the crankshaft position sensor and the coolant temperature sensor are evaluated.
Once the engine speed has reached approx. 500 rpm a transition is made from the fixed ignition timing point to the ignition timing point, electronic map-controlled in line with the momentary operating state.

If less than approx. 7 V no further engine start and no energizing of the ignition coils is possible.

2.2 Catalytic converter heating up (warming-up phase)
The ignition angle is continuously retarded for about 20 seconds in order to bring the catalytic converter more rapidly up to operating temperature if:
^ Coolant temperature at start > 15 °C < 40 °C
^ Selector lever position "P" or "N" (with transmission 722)

2.3 Idle
In order to assist the idle speed control, the ignition angle can be retarded by as much as a 36° crank angle and advanced by as much as a 20° crank angle.
Altering the ignition angle provides more rapid control than altering the position of the throttle valve.

2.4 Intake air and coolant temperature
The ignition time point is retarded at a high load, as a function of the intake air temperature and/or coolant temperature, in order to prevent any knocking tendency at high intake air and coolant temperatures.
Ignition angle adjustment takes place from an:
^ Intake air temperature > 35 °C
^ Coolant temperature >100 °C

The values of the retardation of the ignition angle of intake air temperature and coolant temperature are added together.

2.5 Inertia fuel shutoff
The ignition angle is briefly retarded when combustion is resumed (fuel injection valves actuated (Y62)) in order to prevent a sudden increase in torque.

2.6 Transmission overload protection (for transmission 722)
The ignition angle is briefly retarded during a gearshift operation and the engine torque thus reduced in order to protect the shift elements of the automatic transmission from excessive thermal stresses during power shifts (1-2-1, 2-3-2). The ME control unit is supplied with a signal over the CAN databus by the ETC control unit for this purpose.

2.7 ESP/ASR control mode
In order to reduce the engine torque as rapidly as possible in the ESP/TCS control mode, the ignition angle is retarded before reducing the throttle valve angle.
The information regarding the torque reduction is provided by the ESP control unit via the CAN databus to the ME control unit.

2.8 Smooth engine running analysis
Smooth engine running is constantly monitored in order to protect the catalytic converters from excessive thermal stresses if combustion misfiring exists.
If the smooth engine running analysis detects combustion misfiring, the relevant fuel injector or injectors are no longer actuated after a certain number of misfirings (but not more than two injectors simultaneously).

2.9 Knock control (AKC)
If uncontrolled combustion (knocking) occurs at one or several cylinders, the ignition angle is retarded at the relevant cylinder or cylinders.

Ignition angles can be checked using the STAR DIAGNOSIS.