Import of IFILE Data Files


The addin RS_IFILE is an import filter for UniPlot to access IFILE data files. IFILE data files are created by the combustion analysis systems by the company AVL LIST GmbH. The import filter can handle zipped IFiles.


The installed files are located in the C:\Program Files\UniPlot\AddIn\RS_IFILE directory.

rs_ifile.ic UniScript File
rs_ifile.icl rs_ifile.ic in object code


  • Start UniPlot.
  • Choose File=>Import Data.
  • Choose Type “IFILE-File (.)”.
  • Select one or more IFILE files.

Created NC-File

The NC file contains all channels of the selected IFILE file.

Heat Release Calculation (Hohenberg)

The heat release rate can be calculated during import.

To open the configuration dialog box choose Tools=>IFile Configuration.


The following formula by Hohenberg is used to calculate the heat release rate:

\Delta Q_{1-2} = \frac{1}{\kappa-1} \cdot V_2 \cdot \left[p_2-p_1 \cdot \left(\frac{V_1}{V_2}\right)^\kappa\right]


  • \Delta Q_{1-2}: Heat from 1 to 2, e.g. increment 1° CA in Joule.
  • \kappa: Polytropic index, values in the range 1.3 to 1.4, Example for air: 1.37 for 400 °C, 1.32 for 1000 °C.
  • p_1, p_2: Cylinder pressure in PA
  • V_1, V_2: Volume in m³

The channel name if formed from the channel name of the pressure signal and the prefix dQ_.

The cumulated heat release is calculated as following:

Q = \int{\Delta Q} \cdot dx

The channel name is formed from the channel name of the pressure signal and the prefix IntQ_.

The calculation does not include the heat transfer to the wall. The calculation can be executed with a constant polytropic index or an polytropic index that varies from compression index to expansion index linearly.

Recommended Values for the polytropic index:

  Diesel Gasoline Gasoline DI
Compression 1.37 1.32 1.35
Expansion 1.30 1.27 1.30
Constant Polytropic Index 1.37 1.32 1.35

Raw Data Smoothing: The cylinder pressure signal can be smoothed using a moving average. The number of points for the smoothing window is defined in degree crank angle.

The increment for the calculation should be set to 0.5 degree or 1.0 degree crank angle.


UTC data groups are not supported.


  • R2012.12: Heat Release Rate calculation added.
  • 06.12.2011: The import addin supports zipped IFile files.
  • 10.10.2008: The following features have been added to the IFile Filter: Import of up to 99 operating parameters, long channel names (more than 10 characters), import of calculated channels (these features have been added to the IFile format with IndiCom 1.3)
  • 24.01.2006: Added channels: Cylinder Volume V and V_REL. These channels are only written if the data is crank angle related.
  • 06.04.2005: SPEED, CYCDUR and CYCTIME added. The channels are only written to the NC file if they do not exist in their own data group. Inlet pipe pressure calibration added.
  • 09.12.2022: Time base ifile are now supported.