Ignition system function - GF07.10-P-1005MM

ENGINE 276.9 in MODEL 204, 207, 212 (except 212.095), 218

Function requirements for the ignition system, general points

Circuit 87M ON (engine timing ON)

Ignition system, general points

Each cylinder is equipped with a directly inserted ignition coil (T1). The ME-SFI [ME control unit (N310) reads in the following sensors and signals for the ignition system:

Right knock sensor (A16/1)
Left knock sensor (A16/2)
Hot film MAF sensor (B2/5) engine load (with code (920) Gasoline direct injection with stratified charge)
Intake air temperature sensor (B2/5b1) (model 204, 207, 212), intake air temperature sensor (B2/5b1) (model 218) (for code 920) Gasoline direct injection with stratified charge)
Left and right intake camshaft Hall sensors (B6/4, B6/5), intake camshaft positions
Left and right exhaust camshaft Hall sensors (B6/6, B6/7), exhaust camshaft positions
Coolant temperature sensor (B11/4) (model 204, 207, 212), coolant temperature sensor (B11/4) (model 218)
Intake air temperature sensor (B17) (model 204, 207, 212), intake air temperature sensor (B17) (model 218) (for code 920) Gasoline direct injection with stratified charge)
Intake manifold intake air temperature sensor (B17/1)
Pressure sensor downstream of throttle valve (B28/7), engine load
Crankshaft Hall sensor (B70), engine speed and crankshaft position

The requirements of the torque coordination function are also taken into account.

For the following partial functions, ignition angle adjustment in the direction "retarded" or "advanced" takes place:

Idle speed control
Deceleration fuel shutoff
Transmission overload protection
Knock control
Torque coordination

Function sequence for ignition system

The ME-SFI [ME] control unit sends the signal for the dwell time of the respective operating point to the ignition coil over the actuation line (circuit 4). The respective ignition coil interrupts the primary circuit by means of an integral fuse after expiration of the dwell time. The ignition voltage passes from the ignition coil to the spark plug (R4) and causes arcing in the air gap between the center and ground electrodes.

Determination of the ignition angle takes place dependent on a characteristics map according to the input signals from the ME-SFI [ME] control unit.

Operating mode for the ignition coil

Single spark ignition (on engine 276 DEH)

In the classic operating mode the ignition coil is charged once per ignition process and generates an ignition spark.

For new combustion systems the requests on the ignition also increase. For supercharged engines the ignition coil must provide a high secondary voltage so that an ignition spark can be generated. For a stratified combustion process the ignition timing fluctuates slightly. Ignition coils with high energies can be used to securely ignite the mixture which allow a long spark ignition period.

There is also the option of using several sparks for each ignition process instead of just one spark. This operating mode is called Multispark mode.

Multi-spark ignition (on engine 276 DES)

In contrast to single spark mode many sparks are used in Multispark mode. This is not a series of a number of single sparks occurring one after the other but instead the ignition coil is recharged in-between in order to again provide sufficient energy for sparks.

Multispark ignition begins like a single spark ignition. The ignition coil is supercharged at the beginning up to a desired target primary current. The charging current is switched off at the ignition timing whereby the ignition spark is created. However, the ignition coil is not completely discharged in Multispark mode.

The flowing secondary current which directly depends on the charge level of the ignition coil is measured in the ignition coil. If it drops below the secondary current threshold, the coil electronics switches the power amplifier to conducting again, whereby the charging current flows again.

The level of the flowing primary current is also monitored. If the primary current threshold is reached, the power amplifier closes the primary circuit and it comes again into high voltage generation mode. This produces a further spark. The following sparks are generated according to the same scheme.

In operating mode multi-spark ignition can be run in stratified operation with a strongly leaned out mixture. The advantage is a lower fuel consumption.

Ideal development of the primary and secondary current for a multi-spark ignition

Fig 1: Primary And Secondary Current Graph For Multi-Spark Ignition System

Courtesy of MERCEDES-BENZ USA

Diagnosis

The ignition angles can be checked using the Xentry diagnostics.

Engine configuration and ignition firing order

Fig 2: Identifying Engine Configuration And Ignition Firing Order

Courtesy of MERCEDES-BENZ USA

Electrical function schematic for ignition system	MODEL 204	PE07.10-P-2705-97FAK
	MODEL 207	PE07.10-P-2705-97EAH
	MODEL 212	PE07.10-P-2705-97DAI
	Model 218	PE07.10-P-2705-97XAB
Overview of system components for gasoline injection and ignition system with direct injection	ENGINE 276.9 in MODEL 204, 207, 212 (except 212.095), 218	GF07.70-P-9998MM