In order to appreciate the scavenging process of the through scavenging system, static studies, investigating the flow inside the cylinder under steady-flow conditions, had been carried out. However, the question always arises as to whether the process of scavenging the cylinder is the same as in a running engine. To make clear such problems, some tests were made under dynamic conditions similar to that in the running engine. For the measurment of gas-exchange a new method utilizing the dielectric properties of gases was used². This paper presents the results investigated the effect of air-entry angle on the process of scavenging-the development of scavenging air in the cylinder, its escaping state and the portion in the cylinder at which the products of combustion of one cycle cannot be replaced effectively.