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How to Log BMW MS41, MS42, and MS43 ECUs | TRM Tuning

Logging your BMW’s ECU data is an essential part of remote tuning. If you’re running a TRM Tuning calibration on an MS41, MS42, or MS43 ECU, using RomRaider Logger will allow you to collect real-time engine information safely and accurately. These logs help our tuners fine-tune fuel, ignition, boost, and VANOS parameters for optimal performance. The TRM flasher will do some basic diagnostics and some logging on some ecus like MS41, but for a more complete log RomRaider is the go-to solution.

Download RomRaider: Get the latest version from the official site. Download RomRaider

🧰 What You’ll Need

  • RomRaider Logger (Windows version recommended)
  • BMW INPA/K+DCAN cable (FTDI-based USB cable)
  • Driver package (FTDI/INPA drivers installed)
  • Java Runtime Environment (JRE) – required for RomRaider, and must be 32 bit
  • Windows laptop and stable power supply
  • Your TRM-tuned ECU on MS41 (E36), MS42/MS43 (E46, E39, Z3)

⚙️ Step 1: Install and Configure RomRaider

  1. Download and install the latest RomRaider package.
  2. Install ECU definitions for **BMW MS41–MS43** — these allow RomRaider to recognize your ECU parameters. (Email info@trmtuning.com for the correct ECU definition for your ECU and calibration.)
  3. Connect your K+DCAN cable to the OBD-II port and open Device Manager. Note your COM port number (e.g., COM3).
  4. In RomRaider Logger → Preferences → Connection, enter your COM port and select 9600 or 115200 baud rate (We recommend **115200** for faster communication).

📋 Step 2: Select Logging Parameters

  • Open the **Logger** tab and click **Connect** once the ignition is ON (engine off).
  • Select key parameters:
    • Engine RPM
    • Throttle Position (%)
    • Load / MAF (g/s)
    • Lambda
    • Ignition Timing
    • STFT/LTFT (Fuel Trims)
    • Vehicle Speed
    • IAT
    • Coolant Temp
    • Knock
  • Check that live data displays correctly before recording.

🚗 Step 3: Perform the Logging Run

  1. Find a safe location such as a race track or dyno environment.
  2. Click “Record” in RomRaider Logger.
  3. Start with idle and part throttle driving. Make sure all parameters are within spec before continuing.
  4. Perform one to two wide-open throttle (WOT) pulls from ~2000 RPM to redline in 3rd gear.
  5. Let the car idle for one minute at the end of the log.
  6. Click Stop to end the session and save your .csv log file.

📨 Step 4: Send Logs to TRM Tuning

Email your saved log file to TRM:

Email: tuning@trmtuning.com

Include:

  • Your car model and ECU type (e.g., E46 330i MS43)
  • Fuel octane and any engine modifications (MAF, injectors, turbo, etc.)
  • Your .csv log file from RomRaider

✅ Step 5: Review and Adjustment

The TRM team will analyze your AFRs, fuel trims, timing, and load data to fine-tune your calibration. This step ensures your car runs safely while maximizing power and response.

💡 Logging Tips

  • Always log with a fully warmed-up engine.
  • Make sure your laptop is plugged in — RomRaider can crash on low battery voltage.
  • Keep your driver version consistent (FTDI 2.12.x recommended).
  • Use a battery charger if running multiple pulls during a session.

Accurate logs are the foundation of TRM’s remote tuning precision. By capturing quality data with RomRaider, you enable your tuner to optimize performance for your unique setup.