Functional Description of EGM
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Status September 2003 (EvoBus-Service / AFT) Page: 19 of 83
2.2.1.5 Engine protection: camshaft emergency-running mode
To detect and evaluate the current crank angle and the engine speed, the
M 447 hLAG is equipped with two inductive speed sensors – one crankshaft sensor and one camshaft
sensor. Both speed sensors are evaluated and monitored by the engine control. As the resolution of the
crankshaft sensor is higher than that of the camshaft sensor (more tooth faces on the crankshaft gear),
the crankshaft signal is normally used for determining the crank angle. The camshaft signal is required for
system synchronisation and when the crankshaft signal fails. If the camshaft signal fails before "system
synchronisation" , the engine control switches into the crankshaft emergency-running mode. In the
crankshaft emergency-running mode the so-called dual ignition (two cylinders are ignited simultaneously)
takes place and the torque reduction is carried out as a function of the engine speed. If the camshaft
sensor fails after "system synchronisation" is carried out, engine operation is maintained without
restriction.
Note: To accelerate the engine run-up during starting, starting is carried out with dual ignition (cylinder-
selective gas injection and firing of two cylinders).
Engine protection: Crankshaft emergency-running mode (dual ignition)
Engine speed
Characteristic curve
Dual ignition
Limitation torque
Torque limitation
with dual ignition
Title:
Engine protection
File:
kd_mts_doppelzündung.vsd
Date of last change: 2001-09-12
MOB - Torque limitation with dual ignition / Crankshaft emergency-running mode
Torque [Nm] = f(Speed [rpm])
Torque
Speed
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