Engine History Log

Overview

The Engine History Log is a special type of data-log that is recorded automatically by the ECU. The log records key engine parameters over time, allowing you to review the performance and behavior of the engine during operation. This log is particularly useful for diagnosing issues that may not be apparent during normal data-logging sessions.

Accessing the Engine History Log

To access the Engine History Log, select Engine History Log… from the ECU menu.

Engine History Log Dialog

The Engine History Log dialog displays three main sections:

• Left Panel: Calibration properties showing histogram configuration parameters such as bin start, bin width, and bin count for each histogram
• Center Panel: Histogram views showing graphical representations of recorded data distributions
• Right Panel: Summary information including engine run time, start time, and other key statistics

Histogram Selection

Use the histogram dropdown selector at the top of the center panel to view different histograms recorded in the engine history log. Each histogram displays the distribution of values for a specific parameter (e.g., RPM, Coolant Temperature, MAP, etc.).

Main Actions

Read ECU

Reads the current engine history log from the connected ECU. This retrieves the complete log data including:

• All recorded histogram data
• Engine run time and start time
• Calibration settings

To read the log:

1. Ensure you are connected to the ECU
2. Click the Read ECU button
3. The dialog will update to display the retrieved data

Write ECU

The write operation allows the ECU to be replaced on an engine, whilst retaining the historical data from the previous ECU.

Write ECU writes the currently loaded engine history log to the connected ECU. This operation will overwrite any existing engine log in the ECU.

To write the log:

1. Load or modify an engine history log
2. Click the Write ECU button
3. Confirm the operation in the warning dialog
4. If calibration changes have been made, choose whether to clear modified histograms or clear all data

Clear ECU

Clears all data from the engine history log in the connected ECU, resetting all histogram values and the start time.

To clear the log:

1. Click the Clear ECU button
2. Select Clear all to reset all data and the start time, or Cancel to abort
3. The cleared log will be written to the ECU automatically

If no log is currently loaded, you will be prompted to select the Engine History Log version (0.1 or 0.2) to program to the ECU.

Open File

Opens a previously saved engine history log file from disk.

To open a file:

1. Click the Open File button
2. Navigate to the location of the .gehl file
3. Select the file and click Open

The dialog will display all histograms and summary information from the loaded file.

Save File

Saves the currently loaded engine history log to a file on disk.

To save a file:

1. Ensure a log is loaded (either read from ECU or opened from file)
2. Click the Save File button
3. Choose the destination folder and filename
4. Click Save

Files are saved with the .gehl extension (GEMS Engine History Log Files).

Editing Calibration

The calibration properties panel on the left allows you to modify histogram configuration parameters, including:

• Bin Start: The starting value for histogram bins
• Bin Width: The width of each histogram bin
• Bin Count: The number of bins in the histogram
• RPM Filter: Minimum engine speed for logging
• Pedal Filter: Minimum pedal position for logging
• Value Filter: Maximum value for logging - values above this will be ignored. For example, a coolant temperature value filter of 80 degrees means that the histogram won’t log anything above 80 degrees. This filters out erroneous noise on the value.

Example

The calibration below for Coolant Temperature has:

This will cover the range of 0 degrees to 100 degrees, as shown below, and will only log while the engine speed is above 150 rpm, the pedal is above 80, and the temperature is below 120 degrees.

Modification Effects

When calibration values are modified:

• The histogram view updates to reflect the new bin configuration
• If you attempt to write the modified calibration to the ECU, you will be prompted to either:
  • Clear modified histograms: Only histograms with changed calibration will be cleared
  • Clear all: All histogram data and the start time will be reset

Understanding the Data

The engine history log records histogram data for multiple engine parameters. Each histogram shows how frequently the engine has operated at different values for that parameter. This information is useful for:

• Analyzing engine operating conditions over time
• Identifying common operating points
• Diagnosing performance issues
• Validating calibration strategies
• Monitoring engine health and usage patterns
• Supporting warranty claims with historical data

Supported ECU Models

• EM80
• EM112
• GDI80

Upgrading from v0.01 to v0.02 EHL

If a version 0.01 EHL file is written to the ECU with new firmware, it will automatically upgrade this to version 0.02, extracting the Log Start, Run Distance and Engine Speed histogram data.

To do this:

• Before uploading the new (00x34) CoPro firmware, read the v0.01 EHL from the ECU and save this file.
• Upload the new CoPro firmware.
• Open the saved EHL file and write this to the ECU.

This will now be upgraded to the new EHL file type.