There was a 47 องศา crank angle overlap period of 3 valve in the burned gas transferring process. During this period, the exhaust valve of combustion cylinder and both the intake and exhaust valve of the expansion cylinder were all open, as shown in Fig. 4(b), so the burned gas could be exhausted out of the engine directly. Thus, the gas amount of the burned gas. However, the trapped gas in the expansion cylinder could be expanded to the same volume as the combustion cylinder, because the parameters of all cylinder were the same. Therefore, the gas trapped in the expansion cylinder could be further expanded to form a miller cycle, which may increase the thermal efficiency.