There is a concept that the increase in the temperature of charge in a combustion chamber and the shield of heat transferred through a chamber wall can facilitate the oxidation of soot and reduce the discharge of soot from the engine. In the experiments presented here in, an IDI diesel engine was used to inspect the concept. The engine was installed a bigger sized cylindrical swirl chamber which was equipped with two flat quarts windows, in order to observe the combustion phenomena and to apply the optical measurement. The experiments were carried out using two types of divided chambers, that is, the swirl chamber made of ceramics and that made of steel, to examine the the effects mentioned above. In case of ceramics swirl chamber, the vaporization of fuel oil is promoted more, the vaporized fuel oil spreads more, the ignition delay is shorter, the maximum cylinder pressure, the initial rate of cylinder pressure rise, the initial heat release rate and the maximum heat release rate are higher, the duration of combustion is shorter, the flame spreads more, the region of high flame temperature is 1larger, the stabler combustion is maintained until the flame vanishes, and the soot is distributed in the wider zone than those in that of the steel swirl chamber.