Abstract
In order to elucidate the mechanism of low-speed pre-ignition (LSPI), a new visualization apparatus consisting of a test engine with optical windows and a camera trigger system was developed. The behavior of the spontaneous LSPI was compared with that of the LSPI reproduced by injecting deposit flakes into combustion chamber, and by making heavy knocking once to remove the deposits. From these experiments, it is likely that the deposit particles, peeling off from the combustion chamber and being heated to a high temperature by flame propagation of spark ignition before the LSPI cycle, are the ignition source of the LSPI.
