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Market demand and evolving global legislation are forcing OEMs to improve fuel consumption and reduce CO2 emissions. Downsizing in direct injection gasoline engines has been a common strategy towards achieving this goal, but this requires increased boost pressures to maintain power. The increased boost pressures are creating a new abnormal combustion phenomenon known as Low-Speed Pre-Ignition (LSPI). Lubricants and fuels have been implicated as significant influencers of LSPI frequency and intensity. Part 1 of the series described the development of a statistical approach for measuring and quantifying LSPI activity. This statistical approach was shown to be consistent and repeatable. Part 2 of the series further refined the methodology from Part 1 to reduce the frequency of false positives and negatives. A baseline lubricant was used in both of these papers to demonstrate the robustness of this methodology.

In recent years, an abnormal combustion phenomenon called low-speed pre-ignition (LSPI) has arisen from the downsizing of gasoline engines in order to improve fuel economy and comply with global CO2 legislation. The type and quality of the fuel and lubricant has been found to influence LSPI occurrence rates. A methodology for studying LSPI has been implemented, and a rigorous statistical approach for studying the data from a stationary engine test can provide consistent results as shown in Part 1 of the series. LSPI events can be determined by an iterative statistical procedure based on calculating the mean and standard deviation of peak pressure (PP) and crank angle location of 2% mass fraction burned (MFB02) data, determining cycles with parameters which exceeded n standard deviations from the mean and identifying outliers. Outliers for the PP and MFB02 metrics are identified as possible LSPI events.