Low Speed Preignition in Supercharged SI Gasoline Engines

Abstract

A low speed preignition (LSPI) is one of the critical issues in recent supercharged direct injection SI gasoline engines. LSPI is strongly demanded to be solved because knocking with high intensity which is called “super-knock” or “mega-knock” follows it, and sometimes provides severe engine damage. LSPI is occasional phenomena and is often occurs in a sequential manner intermittently including normal SI combustion cycles. Though some possible sources inducing LSPI have been found and reported, chemical and physical mechanisms of LSPI phenomena have not been cleared in detail, yet. This report reviews some studies and discussed about mechanisms of LSPI in supercharged DISI engines focusing attention on the effects of lubricant oil and its additives on LSPI and the LSPI induced by hot deposit fragments detached from the wall.