ENGINE   137.970

P07.61-2271-09

1...12 Cylinders 1 to 12 N3/10 Motor electronics control unit N91 ECI ignition system mains unit

N92/1 ECI ignition module, right cylinder bank N92/2 ECI ignition module, left cylinder bank

Z7/38 Circuit 87 M1i connector sleeve (voltage supply) a Spark plug, ignition circuit a b Spark plug, ignition circuit b CAN Data bus

Left ignition module (N92/2)		ME-SFI control unit (N3/10), coupling 3		Right ignition module (N92/1)
ion current signal cylinders 7 to 9 Pin 6		Pin 32 Pin 33		Pin 6 ion current signal cylinders 1 to 3
ion current signal cylinders 10 to 12 Pin 7		Pin 45 Pin 46		Pin 7 Ion current signal cylinders 4 to 6
Ground, ion current signals Pin 5	-----	Pin 44 Pin 47	-----	Pin 5 Ground, ion current signals
Ignition trigger signal, cylinder 7 Pin 1		Pin 37 Pin 49		Pin 1 Ignition trigger signal, cylinder 1
Ignition trigger signal, cylinder 8 Pin 2		Pin 2 Pin 1		Pin 2 Ignition trigger signal, cylinder 2
Ignition trigger signal, cylinder 9 Pin 3		Pin 35 Pin 24		Pin 3 Ignition trigger signal, cylinder 3
Ignition trigger signal, cylinder 10 Pin 4		Pin 14 Pin 28		Pin 4 Ignition trigger signal, cylinder 4
Ignition trigger signal, cylinder 11 Pin 13		Pin 38 Pin 50		Pin 13 Ignition trigger signal, cylinder 5
Ignition trigger signal, cylinder 12 Pin 12		Pin 36 Pin 51		Pin 12 Ignition trigger signal, cylinder 6
Ignition offset cylinders 7 to 12 Pin 10		Pin 29 Pin 15		Pin 10 Ignition offset cylinders 1 to 6
Ignition change (ignition circuit a/b) Pin 11		Pin 30 Pin 43		Pin 11 Ignition change (ignition circuit a/b)
		Power pack (N91)
Battery voltage, terminal Pin 15		Pin 13 Pin 12		Pin 15 Battery voltage, terminal
Ground Pin 8	-----	Pin 14 Pin 11	-----	Pin 8 Ground
Auxiliary voltage approx. 23 Pin 14		Pin 8 Pin 7		Pin 14 Auxiliary voltage approx. 23 V
Voltage approx. 180 V Pin 16		Pin 16 Pin 9		Pin 16 Voltage approx. 180 V
Voltage supply
Voltage supply		Pin 4
Circuit 87		Pin 5

The short name for the AC ignition system ECI means: E = Energy (energy) C = Controlled (controlled) I = Ignition (ignition system) Task The ignition system ECI must initiate combustion by creating a spark at the spark plugs. This requires an adequately high voltage for generating a spark at the end of the spark plug and the sparks must also have sufficient energy to ensure guaranteed combustion of the fuel / air mixture. The ignition system must be insensible to carbon fouled spark plugs and guarantee a high spark plug working life.

Design The ignition system ECI consists of: The ignition module ECI for the right cylinder bank The ignition module ECI for the left cylinder bank ECI ignition system mains unit Evaluation circuit for the ion current in the ME control unit Actuation of the ignition system ECI by the ME control unit Ignition map in the ME control unit. No spark tests can be undertaken with the ignition system ECI.

Function The ignition system ECI has the following sub-functions: 1. Generation of the ignition voltage (ac voltage). There is an output stage for each spark plug in the ignition modules. The ignition coils are arranged in the spark plug connectors. The output stages with oscillating circuit generate the ignition voltage from an input of about 180 V. The ME control unit produces the following actuation impulses: Triggering of the ignition spark according to the ignition angle Permanent control of the ignition process Change of ignition Ignition offset

2. Measurement of the ion current. There is a switchover to ion current measurement at the end of the ignition spark phase and the ion current on the spark plug is measured with the help of an auxiliary voltage of about 23 V. Evaluation of the ion current signals takes place in the ME control unit. This is capable of recognising knocking combustion and misfiring. 3. The power pack generates the required voltages of two times about 180 volts and two times about 23 volts.

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Generation of the ignition voltage (ac voltage) 1 Actuation of ignition and ion current uncoupling in the ignition module L1 Primary winding L2 Secondary winding a Actuation of the ME control unit b Ion current signal at ME control unit

C Capacitor D Diode R Resistor TR Transistor U 180 DC voltage approx. 180 V

The ignition voltage is generated in two steps: 1. Transistor (TR) closed - the voltage U180 is transferred to the secondary side. 2. Transistor (TR) opened - the negative half wave of the AC voltage develops and is also transferred to the secondary side. Control of the transistor can theoretically allow generation of an AC voltage of any desired duration and energy level.

The maximum spark burning period is, however, limited by the rated output of the power pack ECI of two times 55 watts depending on the engine speed to about 0.15 to 1.5 msecs. A spark burning period of about 0.1 msecs is usually quite adequate for guaranteed combustion of the fuel / air mixture. The rapid increase in ignition voltage makes the ignition system ECI insensible to carbon fouled spark plugs e.g. due to frequent cold starts.

1.2 Spark duration control Adjustment of the spark energy over the spark duration to the actually required ignition energy of the fuel / air mixture occurs controlled by the ME control unit according to the performance map. With cylinder shutoff at ON the spark duration of the left cylinder bank is reduced to an extremely short time period. The spark plugs enjoy 4 times their usual working life due to spark duration control. Combining this at the same time with the use of spark plugs with platinum electrodes allows the working life to be extended even further. 1.3 Ignition offset and ignition change In the lower part load range up to approx. 2000 rpm both ignition sparks of a cylinder are triggered simultaneously. At moderate and high engine loads, the ignition sparks are triggered offset by as much as 10° crank angle. Here the order of actuation is changed each 720° crank angle in order to achieve even wear of both spark plugs in a cylinder and to prevent one-sided accumulation of deposits in the combustion chamber.

2.0 Measurement of the ion current Ions are created in the flame front during combustion (particles which have various different electrical charges) which balance each other out again in the burnt mixture. The application of a relatively small measuring voltage to the end of the spark plug allows one to measure this ion current through the flame. The measuring voltage is applied to the primary side of the ignition coils (auxiliary voltage of about 23 volts). This gives an AC voltage on the secondary side of about 1 kV with about 65 kHz on the spark plug electrodes. The ion current modulates this voltage. Decoupling and filtering allows one to obtain an ion current signal. This ion current signal gives some indication of the pressure profile in the cylinder with a degree of accuracy which allows one to detect knocking and misfiring. The ion current signal is transferred to the control unit ME for every 3 cylinders. The cylinder concerned in each case is allocated in the control unit ME with the help of measuring windows.

The chemical formula for the creation of ions in the flame is: CH + O CHO+ + e- CHO+ + H2O H3O+ + CO H3O+ + e- H2O + H
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Ion current measurement at the spark plug delivers a signal directly from the combustion chamber without the use of any additional components such as combustion chamber pressure sensors. The measurement is taken after ignition has been initiated by both spark plugs and

a short waiting time. The measurement is only taken on the spark plug which first sparked. The distance between the electrodes does not have any effect on the ion current signal.

A Behaviour pattern of the ion current signal B Behaviour pattern of the cylinder pressure c Knock vibrations d Measuring window position for ion current measurement
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The profiles of the ion current signal and cylinder pressure are the same during combustion. This means that this behaviour pattern can allow the evaluated ion current signal to be used for the following functions Anti-knock control: The maximum performance and economy of running are achieved by an engine when it is run at the knocking limit. Ion current measurement allows knocking to be recognised directly in the combustion chamber and immediately initiates ignition angle adjustment. Knocking sensors are not required.

Misfiring is clearly recognised for all operating conditions and engine speeds. This is used for controlling the spark duration, for spark plug diagnosis, for diagnosis according to OBD or EURO4, for cylinder specific fuel cut-off and for diagnosis of the cylinder shutoff.

	ECI ignition system power pack, location/task/design/function		GF15.15-P-3100L
	Ignition module location/task/design/function		GF15.15-P-3101L
	Motor electronics control unit, location/task/design/function		GF07.61-P-5000F