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Reasons Influencing the Formation of Low-Speed Pre-Ignition

Low-speed pre-Ignition is a problem for many highly boosted engines and is major industry challenge. This article provides an overview of 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 paid, among others, to the type of fuel injection, mixture formation method, compression ratio and piston design as important factors affecting the occurrence of pre-ignition in the case of stochastic self-ignition. Engine operating and its tuning approach were considered for the possibility of low-speed pre-ignition frequency. The relationship of engine lubricating oil composition within the meaning of the oil base group and its additives on the appearance of abnormal combustion is extensively discussed. The impact of different types of detergents was considered in more detail. The article also describes fuel property effects on low speed pre-ignition. The most important fuel properties from the point of view of their confirmed influence on the formation of low speed pre ignition are fuel’s chemical composition, deposit control additives and volatility. The conclusion emphasizes that the operating conditions in a modern downsized, turbocharged gasoline engines can induce a low-speed pre-ignition problem which can lead to destructive super-knock events. It was pointed out 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 is a key factor for further downsizing and improving engine efficiency.
Topic: Engine combustion
Author: Zbigniew Stępień