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BMW DME / Part III / 05 Generation 1: Bosch Motronic M3.1 / M3.3.1…
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Source
DOC 37 § 5
Contents
Bosch Motronic M3.1 & M3.3.1 Architecture (M50B25 & M50B25TU) and 2 more
Systems covered
`M3.1`, `M3.3.1`, `M5.2`, `ME7.2`
Size
0 tables · 2 code/diagrams · ~633 words

Bosch Motronic M3.1 & M3.3.1 Architecture (M50B25 & M50B25TU)

Generation 1 marks BMW’s journey from discrete 8-bit analog/digital hybrid engine controllers to 16-bit RISC microcontrollers with torque-based engine management.

5.1 Bosch Motronic M3.1 & M3.3.1 Architecture (M50B25 & M50B25TU)#

The Bosch Motronic M3.3.1 (famously housed in the "413" ECU hardware casing) powered the single-VANOS M50B25TU inline-six in the E36 325i and E34 525i:

  • Processor: Intel 80C166 / 8051 variant clocked at 12 ext{ MHz}.
  • Storage: Socketed DIP-28 27C512 UV-EPROM (64 ext{ KB} = 65,536 ext{ bytes}).
  • Airflow Measurement: Hot-wire air mass meter (Bosch 0 280 217 110) producing an analog 0\dots 5 ext{V} signal.
  • Ignition: 6 individual ignition coils fired by discrete high-current bipolar power transistors mounted to a heavy aluminum heatsink bar.
┌──────────────────────────────────────────────────────────────────────────────────────────────────┐  
│                   BOSCH MOTRONIC M3.3.1 (0 261 200 413) MEMORY MAP (64 KB)                       │  
├──────────────────────────────────────────────────────────────────────────────────────────────────┤  
│   0x0000 - 0x7FFF (32 KB): 8051 Machine Instructions, Subroutines, ADC Filtering                │  
│   0x8000 - 0x9FFF (8 KB):  Diagnostic Routines, Blink Code Logic, Sensor Limit Tables             │  
│   0xA000 - 0xDFFF (16 KB): PRIMARY ENGINE CALIBRATION (Fuel, Spark, Single-VANOS Thresholds)      │  
│   0xE000 - 0xFFFF (8 KB):  Microcontroller Interrupt Vectors, Program Entry, Checksum (0xFFFE)   │  
└──────────────────────────────────────────────────────────────────────────────────────────────────┘
Single-VANOS Hysteresis Switching Control#

Unlike later continuous VANOS systems, the M3.3.1 operates Single-VANOS as a binary two-position hydraulic solenoid: \text{VANOS State} = \begin{cases} \text{ADVANCED } (+25^\circ\text{ KW}), & \text{if } n_{\text{engine}} > n_{\text{on}}(load) \text{ and } T_{\text{coolant}} > 15^\circ\text{C} \\ \text{RETARDED } (0^\circ\text{ KW}), & \text{if } n_{\text{engine}} > n_{\text{off}}(load) \text{ or } n_{\text{engine}} < n_{\text{idle}} \end{cases} The activation window typically spans 1500\text{ rpm} to 4800\text{ rpm} at engine loads exceeding 3.5\text{ ms} injection duration. At high RPM (>4800\text{ rpm}), the intake cam is shifted back to the retarded position to reduce dynamic overlap and enhance cylinder scavenging at high gas velocities.

5.2 Bosch Motronic M5.2 & M5.2.1 (M62B44 Non-VANOS V8)#

With the launch of the E39 540i and E38 740i featuring the 4.4L M62B44 V8, BMW introduced the Bosch M5.2 / M5.2.1:

  • Flash Transition: Replaced UV-EPROMs with an AMD 28F200 2-Megabit (256 KB) Flash ROM.
  • Immobilizer: Integration of BMW EWS-II / EWS-III rolling-code immobilizer synchronization over the single K-Line interface.
  • Ignition Knock Regulation: Individual cylinder knock recognition utilizing 4 piezoelectric accelerometers mounted in the engine block valley.

5.3 Bosch Motronic ME7.2 Torque-Based Engine Architecture (M62TUB44 V8)#

Represented in the user DAMOS database by E650_000.a2l and BMW ME7.2 X5.dam, the Bosch ME7.2 introduced full Drive-by-Wire (E-Gas) and continuous single-VANOS variable intake camshaft timing to BMW's V8 platform:

┌──────────────────────────────────────────────────────────────────────────────────────────────────┐  
│                   BOSCH ME7.2 TORQUE-BASED CALIBRATION INTERLOCK ARCHITECTURE                    │  
├──────────────────────────────────────────────────────────────────────────────────────────────────┤  
│                                                                                                  │  
│   [ Driver Pedal (PWG) ] ──► [ KFPW / KFWP ] ──► Indicated Torque Demand (misol)                │  
│                                                                │                                 │  
│   [ DSC / ASC CAN 0x153 ] ─► External Torque Limits (mimax) ───┤                                 │  
│                                                                ▼                                 │  
│                                                    Target Charge (rlsol)                         │  
│                                                                │                                 │  
│                                            ┌───────────────────┴───────────────────┐             │  
│                                            ▼                                       ▼             │  
│                                  Throttle Angle (wdks)                    Ignition Angle (zwout) │  
│                                  Via KFMIRL / KFMIOP                      Via KFZW / KFZW2       │  
└──────────────────────────────────────────────────────────────────────────────────────────────────┘
Key ME7.2 Calibration Tables & Formulas#
  1. Target Indicated Engine Torque (KFMIRL):
    • Must match KFMIRL precisely as the mathematical inverse function: KFMIOP(n, KFMIRL(n, mi)) \equiv mi
    • Failure Warning: If a calibrator inflates KFMIRL values without inverse mathematical synchronization in KFMIOP, the ME7.2 torque monitor triggers an internal torque calculation deviation fault (DTC 115 / P1500 - Torque Monitoring Level 2 Limp Mode), cutting electronic throttle angle to 12\% maximum blade opening.
  2. Actual Engine Indicated Torque Calculation (KFMIOP):