Functional Description of EGM
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Status September 2003 (EvoBus-Service / AFT) Page: 40 of 83
2.6 Ignition
The ignition is carried out as cylinder-selective ignition. The ignition is triggered as soon as the system is
synchronised. The procedure for calculating the ignition angle differs considerably from the engine state.
There is a special calculating specification for determining the firing angle in the engine state: Starting, a
different one in the idling mode and another in the partial and full-load operating modes.
2.6.1 Firing angle in starting mode
In the starting mode the firing angle is interpolated from a characteristic curve as a function of the engine
speed and also provided with an offset dependent on the coolant temperature.
2.6.2 Firing angle determination in idling mode
In the idling mode the firing angle is mainly determined by the engine speed. Depending on the engine
speed, one firing angle is interpolated for the warm engine state and one for the cold engine state. The
individual firing angle (for the warm and cold state) are weighted with a factor dependent on the coolant
temperature and added together. In addition, the idling speed is affected by the firing angle.
2.6.3 Firing angle determination in partial-load and full-load mode
In partial and full-load operation the firing angle is interpolated in each case from a map as a function of
the engine speed and the air mass. The full-load firing angle is only accepted when, in addition to the "Full
load" engine state, the coolant temperature also exceeds an applicable full-load threshold. If this is not
the case, then the firing angle from the partial-load map is also used during full-load operation. In the
engine warm-up mode, the firing angle interpolated from the maps can be assigned a firing-angle offset
dependent on warm-up.
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