Functional Description of EGM
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Status September 2003 (EvoBus-Service / AFT)
Page: 25 of 83
Engine protection: oil-pressure warning threshold
MTS - Oil-pressure warning threshold
Oil pressure threshold [bar] = f(Speed [rpm])
P o
il M
IN
Speed
2.2.1.11
Engine protection: overspeed
To protect the engine against operation at an impermissibly high speed ("overspeed"), an overspeed
protection function is implemented in the control unit. This is calculated at intervals of 10 ms regardless
of the engine state. If the engine speed exceeds the threshold of 2,360 rpm for soft speed limitation (DRB
soft), then the overspeed protection function activates the soft speed limitation in the first step. In the
process the throttle valve is moved into the position 2° DK. If the engine speed exceeds the threshold of
2,400 rpm for hard speed limitation (DRB hard), then the overspeed protection function also switches off
the gas injection in the second step until the condition for hard speed limitation is no longer met.
2.2.1.12
Engine protection: exhaust-gas temperature
To protect the catalyst and adjacent components from excessively high temperatures ("Cat fire"), the
exhaust-gas temperature after the catalyst is monitored. Due to malfunctions in the ignition of gas
injection, the catalyst may be flooded with unburned gas. If the catalyst is already at operating
temperature, extremely high temperatures result in the catalyst due to the increased transfer of gas and
residual air. If the exhaust-gas temperature exceeds 650 °C, a warning is set and the available engine
torque is greatly reduced. From 700 °C the red warning lamp and the warning buzzer are actuated and
the vehicle should be stopped as quickly as possible and the engine switched off.
