Advanced Methods to Handle LSPI in TGDI Engines

In order to meet the stringent emission norms like EU6 and EU7 together with CAFÉ/CAFC norms, down-sizing of the engine is one of the thrust areas of focus among the OEMs. To this end, keeping the engine size small but to achieve the required power output, advanced Turbo charged Gasoline Direct Injection engine technology (TGDI) has emerged. However, TGDI technology is susceptible to an abnormal combustion phenomenon termed as Low Speed Pre-Ignition (LSPI) event. This event happens prior to the intended combustion, which causes the catastrophic engine damage. Several studies in terms of simulation and experiments to understand this phenomenon are reported in the literature. The main factors influencing this occurrence are found to be engine design and calibration, fuel types and engine oil formulation (in terms of calcium content). In this paper, advanced methods to handle the LSPI occurrence severity and component level advances in design robustness to avoid the engine damage are reported. The developed techniques include robust piston design, Piston ring design and coating technologies. In overall, the techniques related to engine design to predict the LSPI occurrence in terms of peak cylinder pressure (PCP) and number of events are summarized.