Ignition System Function - GF07.10-P-1005KJ

ENGINE 281.910 in MODEL 453.0/3/4 

Function requirements for the ignition system, general points 

• Circuit 87 (Engine management ON)

Ignition system, general points 

Each cylinder is equipped with a directly inserted ignition coil. The ME-SFI [ME] control unit (N3/10) reads in the following signals for the ignition system:

• Knock sensor (A16)
• Intake camshaft Hall sensor (B6/15), intake camshaft setting
• Coolant temperature sensor (B11/4)
• Charge air temperature sensor (B17/8)
• Pressure sensor downstream of throttle valve (B28/7), engine load
• Crankshaft position sensor (L5), 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
• Knock control
• Torque coordination

Function sequence for ignition system 

The ME-SFI [ME] control unit issues the signal for the dwell time of the respective operating point for cylinder 1 ignition coil (T1/1) to cylinder 3 ignition coil (T1/3) over the actuation line (circuit 4). The respective ignition coil interrupts the primary circuit by means of an integral power amplifier after expiration of the dwell time. The ignition voltage passes from the ignition coil to the spark plugs (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.

The ignition angles can be checked using the Xentry diagnostics.

Operating mode for the ignition coil 

The ignition coil is generally charged for an engine running at its normal operating temperature once per ignition cycle and an ignition spark is generated. Ignition coils with high energies can be used to securely ignite the mixture, also in cold start conditions, which allow a long spark ignition period.

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 to generation of a high voltage. This produces a further spark. The following sparks are generated according to the same scheme.

	Electrical function schematic for ignition system		PE07.10-P-2705-97BBA
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