10 Misfire Detection (optional)
KRONOS 20
49
10
Misfire Detection (optional)
10.1
General
Misfire detection is available as an optional function in KRONOS 20. It is based on the ob-
servation of the speed variation caused by each ignition. Since only speed and power sig-
nals are used, no additional sensor is required.
When (4050
SpeedVarDetectOn
) is active, the control unit calculates a value for speed
variance on the basis of (2000
Speed
) and the sampling value (50
SpeedVarSampleSize
)
while the engine is running and indicates it as (2050
SpeedVariance
). The value changes if
single cylinders misfire. Since speed change is load-dependent even if the engine ignites
correctly, for the error message both a warning and a shutdown characteristic are defined,
both of which are load-dependent.
To determine the parameters for Misfire Monitoring, single cylinders must be switched off
on the engine test stand and the sampling value (50
SpeedVarSampleSize
) must be deter-
mined in relation to (2050
SpeedVariance
).
10.2
Putting into Operation
1.
Let the engine run at rated speed and rated load under normal conditions. All cylinders
must ignite correctly. The function (4050
SpeedVarDetectOn
) must be active and the
functions (4055
MisfireWarnCurveOn
) and (4056
MisfireEcyCurveOn
) must be dis-
abled.
2.
Raise parameter (50
SpeedVarSampleSize
) step by step from 3 to max. 20. Record the
value of (2050
SpeedVariance
) for each step.
3.
Switch off one cylinder, maintaining the load as far as possible.
4.
Repeat step 2 for this load and this switched-off cylinder. In doing so, optimize the fil-
ter constant (51
SpeedVarFilterConst
) used for determining (2050
SpeedVariance
).
The value of (2050
SpeedVariance
) must increase as much as possible in comparison
to normal conditions to achieve maximum sensitivity.
5.
Record the value of (50
SpeedVarSampleSize
) for which the relative increase of (2050
SpeedVariance
) is highest. The best sensibility is found when the relation between
(2050
SpeedVariance
) and misfiring and normal ignition is highest.
6.
Now determine parameter (50
SpeedVarSampleSize
) for the other switched-off cylin-
ders and, if required, for different loads by repeating steps 2 to 5.
7.
Choose the value of parameter (50
SpeedVarSampleSize
) which yields the clearest
relative variation in (2050
SpeedVariance
) under all conditions and represents the best
compromise for the measurements taken under different loads and with different inac-
tive cylinders.
Summary of Contents for E-LES 30
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