Engine management (MR), function

 The engine management (MR) function is described on engine 926.9 (6 cylinder) as an example.

Engine management generally

The engine management includes all processes which are essential in order to achieve economic and ecological engine operation. The necessary computations for the engine management take place in the engine management (MR) control unit (A6). Together with the exhaust aftertreatment (ACM) control unit (A60), the engine management (MR) control unit ensures that the engine runs in a particularly economical, low pollutant and low-noise way under all operating conditions.

One basic function of the engine management is closed-loop control of the diesel injection system. To do this, the engine management (MR) control unit continuously determines the operating condition of the engine (engine rpm, engine temperature, actual torque, etc.) and compares this or the determined actual values with the specified values stored in the characteristics map.

While taking account of the torque request from the drive control (CPC) control unit (A3), the engine management (MR) control unit subsequently calculates the optimal beginning of injection as well as the injection quantity required for combustion. Both values effect when and how long the engine management (MR) control unit actuates the solenoid valves in the respective single injection pump for cylinders 1 to 6 (Y600 to Y605) of the respective cylinder.

Furthermore the engine management also takes over regulation of the exhaust gas recirculation (EGR) and the boost pressure to regulate the fuel injection system as well as controlling of the engine brake.

Upon request from the exhaust gas aftertreatment (ACM) control unit, the engine management control unit takes over control of the coolant flow to the AdBlue® components (for engines with BlueTEC).

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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 the engine management (MR) control unit)

 Fuel temperature sensor

 Oil level sensor

 Crankshaft position sensor

 Camshaft position sensor

 Coolant temperature sensor

 Charge air pressure and temperature sensor

The torque request that is calculated by the drive control (CPC) control unit is passed on to the engine management (MR) control unit via drive train CAN. This transmits the current actual torque and the maximum torque possible to the drive control (CPC) control unit. Information is also transferred with the flame starting system (FLA) control unit via drive train CAN.

The drive control (CPC) control unit can also be used to exchange information with other electronic systems or control units that are networked with each other via the CAN and the LIN data bus systems.

Through actuation of the engine start and engine stop button, a signal is sent to the engine management (MR) control unit as to whether the engine should be started or stopped. If the engine start button is pressed and held in idle, the engine management (MCM) control unit automatically increases the engine rpm up to the maximum governed rpm.

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For closed-loop control of the fuel injection system, the engine management (MR) control unit actuates the following component parts according to the operating status of the engine and the torque request from the drive control (CPC) control unit:

 Cylinder 1 single injection pump

 Cylinder 2 single injection pump

 Cylinder 3 single injection pump

 Cylinder 4 single injection pump

 Cylinder 5 single injection pump

 Cylinder 6 single injection pump

To activate the engine brake and regulate exhaust gas recirculation (EGR), the engine management (MR) control unit takes on actuation of the following component parts:

 Hydraulic constant throttle solenoid valve

 Exhaust gas recirculation positioner

 If a fault occurs on drive train CAN or on a system component for engine management, the engine management (MR) control unit proceeds according to a clearly defined pattern depending on the severity of the fault. It therefore makes use of substitute values in the case of less serious faults, e.g. a sensor failure, whereas it switches to limp-home mode in the case of serious faults, e.g. a drive train CAN failure.

 The engine management (MR) control unit is a component part of the DAS. If the engine management (MR) control unit is replaced, this must be taught in via diagnostics in the DAS.