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A fundamental examination was made of gasoline-fueled homogeneous charge compression ignition (HCCI) combustion under various compression ratios, intake temperatures and intake gas compositions. The results revealed the basic combustion characteristics, and the ignition timing and combustion duration were found for every set of conditions. Suitable intake air temperatures were also determined for every operating condition. Internal residual gas was used to raise the mixture temperature in the cylinder. The region of maximum engine speed was expanded without heating the intake air. Minimum and maximum indicated mean effective pressures (IMEP) were found in several engine speed regions under several residual gas rates. Based on the results, a comprehensive interpretation is given of conventional HCCI combustion in 2- and 4-stroke gasoline engines.

This paper presents a study of antiknock performance under various octane numbers and compression ratios in a direct injection spark ignition (DISI) gasoline engine. The relationship between the octane number and engine performance in the DISI engine-the engine torque and the break specific fuel consumption (BSFC)-was investigated in comparison with a multipoint injection (MPI) engine. Due to the improvement in the charging efficiency and the advance of the ignition timing by cooled aspiration, the engine torque of the DISI engine was improved over that of the MPI engine. It was also found that the octane number requirement (ONR) was reduced. In addition, the possibility of engine performance enhancement at high compression ratios was studied. At high compression ratios, the engine torque is reduced due to the heavy knocking when low octane gasoline is used. However, an improvement in the engine torque has been observed with high octane gasoline.