Engine management, function

The term engine management describes all processes that are essential to ensure economic and ecological engine operation.

The necessary computations for engine management take place in the engine management control unit.

Together with the exhaust aftertreatment (ACM) control unit (A60), it ensures that the engine runs in a particularly economical, low-pollutant and low-noise way under all operating conditions.

Furthermore, engine management regulates exhaust gas recirculation (EGR) and boost pressure to regulate the diesel injection system as well as controlling the engine brake.

Further controlling, such as fan speed or coolant pump speed, occurs depending on the vehicle equipment.

Upon request from the exhaust gas aftertreatment control unit, the engine management control unit takes over control of the coolant flow to the AdBlue® components or the active regeneration of the diesel particulate filter (DPF).

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The operating condition of the engine is basically determined based on input signals from the following sensors:

 Atmospheric pressure sensor (in engine management control unit)

 Crankshaft position sensor

 Camshaft position sensor

 Fuel temperature sensor

 Oil pressure sensor

 Exhaust coolant temperature sensor

 Fresh air differential pressure sensor

 Charge air pressure and temperature sensor

 Charge air temperature sensor in charge air distributor

 Rail pressure sensor

 Fan rpm sensor

The values of the oxygen sensor are needed only for control of exhaust gas recirculation (EGR). The position of the exhaust gas recirculation positioner is taken into account for closed-loop control of the exhaust gas recirculation (EGR) as well as for controlling the largest possible engine brake stage.

At the outlet of the compressor of the high-pressure stage of the two-stage exhaust gas turbocharger, the air temperature is recorded via the charge air temperature sensor in the compressor housing. The sole purpose of this is to protect the high-pressure-stage exhaust gas turbocharger from excessively high thermal load. The charge air temperature sensor in the compressor housing is therefore installed only in engine 936.916 with two-stage charging.

The torque request is calculated by the drive control unit on the basis of the position of the accelerator pedal, among other things. The signal reaches the engine management control unit via the drive train CAN; for its part, the engine management control unit sends the current actual torque and the possible maximum torque to the drive control unit.

Information is additionally exchanged with the exhaust gas aftertreatment control unit, transmission control unit (TCM) (A5) and retarder control unit (RCM) (A11) via the drive train CAN.

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To regulate the diesel injection system, the engine management control unit activates the following actuators depending on the engine's operating state and the torque request from the drive control unit:

 Cylinder 1 fuel injector

 Cylinder 2 fuel injector

 Cylinder 3 fuel injector

 Cylinder 4 fuel injector

 Cylinder 5 fuel injector

 Cylinder 6 fuel injector

 Pressure regulator valve

 Quantity control valve

To control the exhaust gas recirculation (EGR) and the boost pressure it takes on actuation of the following assembly parts:

 Exhaust gas recirculation positioner

 Boost pressure positioner

Depending on the engine brake stage, the engine management control unit actuates the engine brake solenoid valve to activate the engine brake.

In the largest engine brake stage, the exhaust gas recirculation positioner and the boost pressure regulator are also actuated.

If a fault occurs on the drive train CAN or on a system component for engine management, the engine management control unit proceeds according to a clearly defined pattern depending on the severity of the fault. In the case of less serious faults, e.g. a sensor failure, it resorts to using substitute values. In the case of serious faults, e.g. failure of the drive train CAN, limp-home mode is activated.

As a result, the vehicle can still be driven to the nearest workshop if there is a fault in the system.