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Stochastic Preignition (SPI) is an abnormal combustion event that occurs in a turbocharged engine and can lead to fuel economy losses and engine damage, and in turn result in customer dissatisfaction. It is a significant limiting factors on the use and continued downsizing of turbocharged SIDI gasoline engines. Understanding and mitigating all the factors that cause and influence the rate and severity of occurrences is of critical importance to the engine’s continued use and fuel economy improvements for future designs. Previous studies have shown that the heavy molecular weight components in the fuel are one factor that influences the rate of Stochastic Preignition from a turbocharged SIDI gasoline engine. All of the previous studies have involved looking at the fuel’s petroleum hydrocarbon chemistry, but not specifically at the additives that are put in the fuel to protect and clean the internal components over the life of the engine.

In order to further understand the sequence of events leading to stochastic preignition in a spark-ignition engine, a previously developed experimental and analysis methodology was used to evaluate the propensity of fuels to establishing propagating flames under conditions representative of those at which stochastic preignition (SPI) occur. A large fuel matrix including single component hydrocarbons, binary and tertiary mixtures, and real fuel blends was evaluated. The propensity of each fuel to establish a flame was correlated to multiple fuel properties and shown to exhibit consistent blending behaviors. No single parameter strongly predicted a fuel’s propensity to establish a flame, while multiple reactivity-based parameters exhibited moderate correlation. A two-stage model of the flame establishment process was developed to interpret and explain these results.

Gasoline soot tendency has been extensively studied in last five years. Many tools has been developed to provide indications of a fuel’s sooting tendency. While some methods still have room for improvement, the tools can be used to qualitatively assess the fuel quality in markets. This paper will review the most recently developed methods, with good correlation agreement to vehicle particular emission tendency, that could be used to give indication of the sooting tendency of the gasoline range fuels, and last five years market trend as indexed by those tools. In addition, the paper will review and propose improvement of the methods on assessment of a gasoline range fuel’s sooting tendency. Areas around the globe where market gasoline range fuels are of concern will be highlighted, in coordination with the new emissions regulations.

Stochastic or Low-Speed Preignition (SPI or LSPI) is an undesirable abnormal combustion phenomenon encountered in spark-ignition engines. It is characterized by very early heat release and high cylinder pressure and can cause knock, noise and ultimately engine damage. Much of the focus on mitigating SPI has been directed towards the engine oil formulation, leading to the emergence of the Sequence IX test and second-generation GM dexos® oil requirements. Engine design, calibration and fuels also contribute to the prevalence of SPI. As part of a recently completed research consortium, a series of engine tests were completed to determine the impact of fuel composition on SPI frequency. The fuel blends had varying levels of paraffins, olefins, aromatics and ethanol.

The Particulate Matter Index (PMI) is a helpful tool which provides an indication of a fuel’s sooting tendency. Currently, the index is being used by various laboratories and OEMs as a metric to understand the gasoline fuels impact on both sooting found on engine hardware and vehicle out emissions. This paper will explore a new method that could be used to give indication of the sooting tendency of the gasoline range fuels, called the Particulate Evaluation Index (PEI), and provide the detailed equation in its initial form. In addition, the PEI will be shown to have a good correlation agreement to PMI. The paper will then give a detailed explanation of the data used to develop it. Initial vehicle PM/PN data will also be presented that shows correlations of the indices to the vehicle response.

Gasoline Direct Injection (GDI) has become the preferred technology for spark-ignition engines resulting in greater specific power output and lower fuel consumption, and consequently reduction in CO2 emission. However, GDI engines face a substantial challenge in meeting new and future emission limits, especially the stringent particle number (PN) emissions recently introduced in Europe and China. Studies have shown that the fuel used by a vehicle has a significant impact on engine out emissions. In this study, nine fuels with varying chemical composition and physical properties were tested on a modern turbo-charged side-mounted GDI engine with design changes to reduce particulate emissions. The fuels tested included four fuels meeting US certification requirements; two fuels meeting European certification requirements; and one fuel meeting China 6 certification requirements being proposed at the time of this work.

The impact of gasoline composition on vehicle particulate emissions response has been widely investigated and documented. Correlation equations between fuel composition and particulate emissions have also been documented, e.g. Particulate Matter Index (PMI) and Particulate Evaluation Index (PEI). Vehicle PM/PN emissions correlate very well with these indices. In a previous paper, global assessment with PEI on fuel sooting tendency was presented [1]. This paper will continue the previous theme by the authors, and cover China gasoline in more detail. With air pollution an increasing concern, along with more stringent emission requirements in China, both OEMs and oil industries are facing new challenges. Emissions controls require a systematic approach on both fuels and vehicles. Chinese production vehicle particulate emissions for a range of PEI fuels are also presented.