An Improved Approach to Saving Cylinder Pressure Data from Steady-State Dynamometer Measurements

Cylinder pressure analysis in internal combustion engines involves measuring very large quantities of data, typically 2 Mbytes per test point. Derived results, such as peak cylinder pressure, IMEP and burn angles can be calculated either in real-time or by post-processing of the pressure data and the need for long term saving of the raw data after processing is then optional. Despite the many advantages of retaining the raw data, this is often not done because of the necessity for large capacity storage systems and the time required to transfer the large files across networks. The ideal situation would be to save the derived results and statistical parameters plus the raw pressure data in a much more efficient format which offers substantially smaller data files without significant loss of accuracy and functionality.

The work described in this paper describes techniques for reducing the steady-state cylinder pressure data file size using variable crank angle resolution and assuming mean cycle characteristics are applicable over part of the engine cycle. The effect of using this approach to store just 10% of the usual quantity of data is then demonstrated using pressure data measured for a wide range of engine test conditions. Comparison between the original and reduced pressure data reveal negligible differences in the pressure diagram and derived data confirming that the benefits of saving raw pressure data can be achieved without the usual penalty of very large data file size.