In the case of two-stroke cycle gasoline engines, it is a rather well known fact that under light-load operation they do not run smoothly, but have a high concentration of unburned hydrocarbons (HC) in the exhaust gas, as well as high a fuel consumption rate.
In the study to improve such unstable conditions by devising a scavenging process of the engine, we often encountered self-ignited combustion, a kind of “RUN-ON”. This combustion was found to be very stable and fine with low missions of HC, and improved fuel consumption.
A study was carried out on this self-ignited combustion by optical analysis. Many differences were observed between self-ignited combustion and conventional spark ignited combustion on the behavior of formation of chemical intermediate products before and after ignition.
Self-ignited combustion has been found to occur under relatively low cylinder pressure and temperature, compared to diesel engine combustion, presumably by virtue of intermediate products. This special self-ignited combustion is named “TS (Toyota-Soken) combustion”.