Powertrain Management: Description and Operation
PURPOSE
The Digital Motor Electronic (DME) systems (1.7), provide precise control of fuel injection, ignition and emission control systems to ensure optimum performance and strict emission compliance.
DME And EML Diagram:
OPERATION
The BMW V12 engine uses two Motronic (DME) engine control systems. DME control unit 1 controls cylinders 1-6, and DME control unit 2, cylinders 7-12. Each Motronic system is complete and independent of its counterpart and is capable of running the engine on 6 cylinders in the event of a system failure. An electronic throttle control system (EML), controls throttle operation and coordinates the separate DME systems. Various engine sensors and other systems (i.e.. air conditioning, auto transmission etc.) supply each DME control unit with operating information. The DME control units process the input information and send output signals to adjust injector pulse width and ignition timing.
V12 Component Location:
NOTE: To achieve good mid-range torque characteristics, long air intake pipes are used. This method of induction requires that the plenum chamber for the left bank (cylinders 7-12) be mounted on the right side of the engine, and the plenum for the right bank (cylinders 1-6) be mounted on the left side of the engine. Technicians must keep this in mind when referring to component locations and testing procedures. Components such as air intake sensors, air mass sensors, injectors, throttle position motors and induction systems may be misdiagnosed because of the possible confusion. Remember that fault codes will always refer to the DME system (DME system 1 = cyl. 1-6) and (DME system 2 = cyl. 7-12).
Input signals include:
^ Engine Speed
^ Reference Mark Signal
^ Mass Air Volume
^ Intake Air Temperature
^ Coolant Temperature
^ Cylinder Identification
^ Throttle Position
^ Lambda Signal
^ Battery Voltage
^ Vehicle Speed
^ Gear Position (Auto Trans. only)
^ On-Board Computer (OBC)
^ A/C Signal
Output Signals include:
^ Fuel Injection Control
^ Ignition Control
^ Fuel Pump Control
^ Evaporative Control
^ Throttle Motors
ON-BOARD DIAGNOSTICS
In the event of a DME system malfunction, circuit information will be stored in the internal memory of the DME control unit. Intermittent failures are stored with a record of the failure frequency.
The DME control unit is able to store up to thirty malfunctions and will give priority to those items which can cause the vehicle to exceed exhaust emission standards. In addition to being stored in memory, an emissions-related failure will cause the "Check Engine" light to illuminate on the instrument cluster.
ADAPTIVE CONTROL
The DME control unit has adaptive idle speed and air/fuel mixture and purge control capabilities. The control unit continuously compares the programmed data for idle control and air fuel mixture with the input values.
If a deviation occurs, the new input values are superimposed and stored in the programmed data map. As a result, new output signals are sent to the idle control valve and or to the injectors. This allows the DME control unit to correct the idle speed or injector pulse width for break-in wear or slight air leaks which might occur in the systems.
If power is interrupted to the control unit, new adaptation takes place within several minutes of engine operation.