Ca Additive and In-cylinder Condition on Promotion of Abnormal Combustion in Supercharged SI Engine

　The downsizing engine is popular in the field of SI engine. However, one of the problems is the abnormal combustion so called LSPI. 　A lot of researchers have been reported about the mechanism of LSPI. One of the sources of LSPI would be the lubricating oil droplet in cylinder. To avoid LSPI, it has been adjusted the ingredients of oil additive in lubricating oil. However, many kinds of fuels will be adapted to the SI engine on the point of CO2 emission in the future. So, it would be needed that the mechanism of LSPI would be cleared essentially. It has been reported that the ingredients of oil additive strongly effect on the occurring the LSPI. There are two information in our previous research. First, the data shows that frequency of abnormal combustion is 1/10 of frequency of scattering lubricating oil from the piston crown. 　Seconds, autoignition timing of scattering lubricating oil is almost at ATDC, however several its autoignition proceed the timing for BTDC continuously. 　Here, this research focuses on the effect of Ca additive in lubricating oil on the frequency and timing of autoignition which is conducted to the LSPI.