23.12
Cylinder balancing
An even gas admission duration setting for all gas admission valves
will not result in exactly the same gas quantity in all cylinders, due to
the geometry of the engine and due to some deviations in the gas valve
performance. This slight disparity is handled with the cylinder balanc-
ing control. The MCU compares each cylinder’s exhaust gas tempera-
ture with the average exhaust gas temperature of the entire engine,
and adjusts the duration of the individual gas valves with an offset, in
order to minimise the deviation. There are limitations for the maxi-
mum adjustment available in order to prevent that possible component
failures cause a too rich or too lean gas/air mixture. Above an engine
load level of approximately 75 % (tuneable) this compensation is
disabled, and the duration offset will be determined according to fixed
values. The knock control algorithm of WECS will also affect the gas
admission duration. The cylinder exhaust gas control is not active in
diesel- and backup operating mode.
If the engine is in gas operating mode, and the load level is above
approximately 15 % (tuneable) a cylinder knock based control will
enable. Light knock in any cylinder will immediately result in a slight
reduction of the quantity of gas injected into that cylinder. In order to
maintain the same engine load level, the speed/load controller will
automatically increase the gas admission into other cylinders. When
the situation normalises in the cylinder, the gas admission will slowly
be restored to the original setting. This process is continuous, and keeps
the cylinders slightly out of knocking conditions. This process will
ensure that the efficiency of the engine is at optimal levels.
Cylinder balancing control
CCM
KDU
Main gas
control valve
T
a
offset
CAN
CAN
Exhaust gas
temp.
MCU
average calc.
+ knock offset
calculation
Profibus
Exhaust gas temp
Exhaust gas temp
Cylinder knock
Cylinder knock
Cylinder knock
Fig 23-22
34SG-200408-01
WECS 3000
