BMW E36 MS41.1 / MS41.3 Datalogging

Datalogging lets you see what the ECU is doing while the engine is running.

Use logs before and after tuning changes so adjustments are based on actual data instead of guesswork.

This guide applies to BMW E36 M52 and M50/M52-based builds using MS41.1 or MS41.3.

What to Log

For most MS41 tuning, monitor:

• RPM

• Engine Load

• MAF Airflow

• MAF Voltage

• Injector Pulse Width

• AFR / Wideband

• Short-Term Fuel Trim

• Long-Term Fuel Trim

• Ignition Timing

• Knock Retard

• Coolant Temperature

• Intake Air Temperature

For MS41.3, also log:

• Load.x

• MAF.x

These extended values are important when tuning the MS41.3 extended tables.

COM Port Settings

Use:

• Bits per second: 9600

• Data bits: 8

• Parity: None

• Stop bits: 1

• Flow control: None

If using an FTDI-based cable, open Advanced and set:

• Latency Timer: 1 ms

Make sure the selected COM port belongs to your USB tuning cable and not a Bluetooth serial device.

Basic Logging Workflow

1. Connect the tuning cable.

2. Confirm the correct COM port.

3. Open RomRaider Logger.

4. Select the parameters you want to monitor.

5. Warm the engine fully.

6. Start the log.

7. Perform the test or pull.

8. Stop and save the log.

9. Review the data.

10. Make one controlled tuning change at a time.

Useful Log Types

Idle Log

Use for:

• Fuel trims

• Idle quality

• Injector scaling

• MAF accuracy

Cruise Log

Use for:

• Part-throttle fueling

• Fuel trims

• MAF calibration

• Closed-loop behavior

WOT Log

Use for:

• AFR

• Engine Load

• MAF

• Injector Pulse Width

• Ignition Timing

• Knock Retard

Logging for MAF Tuning

For MAF tuning, collect multiple logs across different RPM and load areas.

Use:

• Steady throttle

• Low to high RPM

• Multiple load ranges

• Closed-loop operation where possible

• WOT enrichment OFF while collecting MAF correction data

Note: To help fill higher-load areas of the MAF table, use light foot-brake pressure during a smooth pull from the lowest usable RPM in a gear up to redline. Avoid excessive brake pressure or brake overheating.

MS41.3 Extended Logging

When using MS41.3, include:

Load.x

MAF.x

These values represent the extended load and airflow calculations used by the MS41.3 tuning strategy.

Review the Log

Do not judge the tune from one value alone.

Review how these work together:

• AFR

• Load

• MAF

• Fuel trims

• Injector Pulse Width

• Ignition Timing

• Knock Retard

The goal is to understand what the engine and ECU are doing under the same operating conditions before and after each tuning change.

Save Your Logs Clearly

Keep test conditions as consistent as possible.

Use clear file names, for example:

Idle_Log_01

Cruise_Log_01

WOT_Log_01

MAF_Log_01

This makes it easier to compare changes between tune revisions.