Reasons influencing the formation of low-speed pre-ignition

Low-speed pre-ignition (LSPI) is a problem for many highly boosted engines and constitutes a major industry challenge. This paper provides an overview of the reasons that might lead to low-speed pre-ignition. These reasons have been systematized and divided into four groups related to the engine, fuel, lubricating engine oil, and engine operating conditions. In the case of the engine, particular attention was drawn, among others, to the type of fuel injection, the method of mixture formation, the compression ratio, and piston design as important factors affecting the occurrence of pre-ignition in the case of stochastic self-ignition. The paper analyzes the influence of the engine operation and the adjustment of its operating parameters on the frequency of occurrence of low-speed pre-ignition. The paper extensively discusses the relationship between the engine lubricating oil including the oil base groups and its additives and the occurrence of abnormal combustion. The impact of different types of detergents was considered in more detail. The paper also describes the effects of the fuel properties on low-speed pre-ignition. The most important fuel properties from the point of view of its confirmed influence on the formation of low-speed pre-ignition are the its chemical composition, deposit control additives and volatility. The conclusion emphasizes that the operating conditions in a modern downsized, turbocharged gasoline engine can induce a low-speed pre-ignition problem, which can lead to destructive super-knock events. It was indicated that low-speed pre-ignition tends to become more prominent in the operating regime that is most beneficial to attaining improved fuel economy. Therefore, the solution to this problem is considered to be a key factor in further development of downsizing and improving the engine efficiency. An innovative element of the article, which distinguishes it from other similar articles, is the proposed logical division and systematization of the hitherto identified factors influencing the LSPI phenomenon. This has been done by separating, comprehensively listing and ordering these factors