Digital engine electronics

The Digital Engine Electronics (DME) are attached to the intake system close to the engine. This means the Digital Engine Electronics (DME) are cooled by the intake air. The design of the plug connections between the wiring harness and the DME digital engine electronics module ensures they remain sealed against water when the connectors are plugged in.

The DME digital engine electronics module furnishes the power to the sensors and actuators directly. The top side of the Digital Engine Electronics (DME) is simultaneously the lower section of the air intake system. There is a contour on the housing beside the intake pipe which assures optimum flow conditions into the intake system.

The Digital Engine Electronics (DME) is the computing and switching center of the engine control system. Sensors on the engine and vehicle deliver the input signals. The signals employed to control the actuators are calculated using the input signals and the specified setpoint values stored in the Digital Engine Electronics (DME) as well as the characteristic maps. The DME digital engine electronics module activates the actuators directly or via relays.

Two sensors are located on the DME digital engine electronics module's printed circuit board:

• 1 Temperature sensor
• 1 Ambient barometric pressure sensor.

The temperature sensor monitors the thermal condition of the components in the DME digital engine electronics system.

The ambient pressure is required for calculation of the mixture composition.

The following graphic shows the engine N55 as example.

Fig 1: Identifying Digital Engine Electronics System Components

Courtesy of BMW OF NORTH AMERICA, INC.

In principle, 2 groups of bus systems are distinguished:

• Main bus systems: FlexRay, K-CAN, K-CAN2, MOST, PT-CAN and PT-CAN2
• Sub-bus systems: LIN, BSD, K-bus (body bus) and Local-CAN.

Main bus systems are responsible for the inter-system data exchange between the control units. This also includes the system functions 'diagnosis', 'programming' and 'coding'.

Sub-bus systems exchange data within a function group.

The communication of the Digital Engine Electronics (DME) with the other control units takes place via the following data buses:

• FlexRay

  FlexRay enables reliable, real-time data transfer between the electrical and mechatronic components. FlexRay contains a powerful protocol for data interchange with real-time capability. With a maximum data rate of 10 MBit/s per channel, the FlexRay is very fast. The central gateway module (ZGM) sets up the link between the various data buses and the FlexRay.

• PT-CAN (drive train CAN)

  PT-CAN is the name of the data bus on the drive train. The data rate of the PT-CAN is 500 kBit/s and the PT-CAN is configured as a linear two-wire bus.

• PT-CAN2 (powertrain CAN2)

  As of the F01, the PT-CAN is supplemented by the PT-CAN2. The data rate of the PT-CAN is also 500 kBit/s and the PT-CAN2 is configured as a linear two-wire bus.

• LIN bus (Local Interconnect Network bus)

  The LIN bus is a standardized serial single-wire bus. The LIN bus supplements other data buses and it is used for communication between the different control units.

  The LIN bus is used, for example, for the intelligent battery sensor (IBS) and the alternator.

  The data rate of the LIN bus is 19.6 kBit/s.

• BSD (Bit-Serial Data interface)

  The BSD networks the components of the drive unit electronics. The BSD is a bidirectional single-wire interface.

  The data rate of the BSD is 9.6 kBit/s.

• K-bus (body bus)

  The K-bus (body bus) networks the components of the general motor vehicle electrics, the information and communications systems and the safety system. The K-body bus is a bidirectional single-wire interface.

  The data rate of the body bus is 9.6 kBit/s.

• Local-CAN

  The Local-CAN is a bidirectional single-wire interface.

  The Local-CAN is used, for example, for the nitrogen oxide sensor.

  The data rate of the Local-CAN is 9.6 kBit/s.