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In this paper, a SI-HCCI combustion mode switch is investigated. The main challenge in switching is how to change the in-cylinder conditions (for example, A/F ratio, and internal EGR), which are different in SI and HCCI combustion. For mode switching without variations of BMEP and engine speed, we propose a new switching method. The concept of the proposed method is as follows: During switching between SI and HCCI, the A/F ratio and the internal EGR rate of each cylinder are controlled strictly by coordinating the variable valve systems and the throttle valve angle. In addition, the proposed method uses both an advance in spark timing and double fuel injection in order to stabilize combustion. From the experimental results, using a multi-cylinder test engine with variable valve systems and a direct fuel injection system, the variations of BMEP in switching were suppressed to 0.4 bar or less. Finally, the transitions of in-cylinder conditions during switching are examined.