This function supplies the ignition angle retarded as much as possible zwspae and the most retarded ignition-angle efficiency
etazwmn for the ignition-angle limitation.
The ignition angle retarded as much as possible is either calculated from the combustion limit KFZWMN, a special catalyst heating
map or from the engine protection map. The catalyst heating map is activated optionally via the code word CWKHZW dependent on
the catalyst heating concept and on the combustion behavior of the engine.
The map KFZWMN contains the absolutely most retarded ignition angle, at which the engine still combusts. The ignition angles
result, if the permissible temperature in the exhaust manifold is being exceeded or if combustion misses occur in the engine
due to the retarded position of the ignition angle.
Clearly audible combustions can be observed in the exhaust-system branch during start and during post-start with the ignition
angles in KFZWMN. This longer afterburning at cold engine and bad carburation is compensated by the ignition angle at start
resp. by the map KFZWMNST. KFZWMNST resp. the ignition angle at start zwstt is controlled down via a ramp to KFZWMN during the
post-start. Via the characteristics KLFZWMNST resp. KLFZWMNKH the duration in seconds is set, which is needed by the ramp to
travel from a factor zero to 100%. If the catalyst heating reserve fmdkh has been completely built-up, the control duration is
set via a catalyst heating characteristic.
KFZWMNST/ZWSTT limits the lift of the torque control into the direction retarded in the speed overshoot during the transition
from start to idle.
Afterburning occurs more often in the exhaust-system branch at cold temperatures, therefore it is often useful to perform a timing
advance on the most retarded ignition angle at cold engine. The shift of the retarding limit via tmot is performed in DZWSPM.
If retarded ignition angles are needed for the catalyst heating function immediately after the start, then these can often only be
driven in an rl,nmot-window. In case of load change e.g. such a catalyst heating angle can lead to distinct noise in the exhaustsystem
branch. A special catalyst heating limitation of the ignition angle can for this reason be performed via KFZWMNKH.
The engine protection map is activated, if the ignition angle was more retarded than the engine protection ignition angle for
longer than a debouncing time.
The most retarded ignition angles calculated from the maps are checked for long-term compatibility in another calculation step.
That means, an angle KFZWMS that in the long-term does not lead to the engine being damaged may not be exceeded. If fuel cut-off
is active or if the automatic transmission requests a torque reduction, the engine protection check is deactivated.
Activation and deactivation of the engine protection check are delayed via time constants to prevent jittering of the
ignition angle, when the most retarded ignition angle is reached.
If the engine protection check is active, then the ignition angle is controlled via a ramp to the value in KFZWMS, provided
it is less than the value in KFZWMS. The increasing control is performed during the post-start phase. If catalyst heating, keeping
catalyst warm or torque reduction is performed there by transmission intervention, then immediately branching to the most retarded
ignition angle from the combustion criteria is performed in this phase.
The ignition angle is controlled down to zwmnd again, if the engine protection check is deactivated. If transmission
intervention occurs during the decreasing control phase, an immediate jump to zwmnd takes place.

Hello Littco,

I don't understand how does Motronic chosse bettween KFZWMN or KFZWMS.