Digital engine electronics

The Digital Engine Electronics (DME) are housed in an electronics box inside the engine compartment.

The Digital Engine Electronics (DME) supply the voltage to the sensors and most of the actuators directly.

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 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.

Fig 1: Digital Engine Electronics Components

Courtesy of BMW OF NORTH AMERICA, INC.

In principle, 2 groups of bus systems are distinguished:

• Data bus: FlexRay, K-CAN, K-CAN2, MOST, PT-CAN and PT-CAN2
• Sub-bus: LIN

Main buses are responsible for the inter-system data exchange between the control units. This also includes the system functions diagnosis, programming and encoding.

Sub-buses exchange data within a functional 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 (BDC) sets up the link between the various data buses and the FlexRay.

• PT-CAN (Powertrain 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)

  PT-CAN2 is the name of the second data bus on the drive train. The data rate of the PT-CAN2 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 data rate of the LIN bus is 19.6 kBit/s.