•  The zero-overlap side exhaust port system has structurally reduced the mixing of exhaust gas in the intake air process. When the position of the rotor is at top dead center (TDC) of exhaust, the intake ports and exhaust ports are closed by the side surfaces of the rotor. However, exhaust gas flows into the intake air port passing through the minute gap between the rotor and the side housing. To prevent this, exhaust gas has been blocked from flowing into the intake air process by a cut-off seal set between the oil seal and side seal.

•  A gas seal is maintained against the housing friction surface by the addition of a spring between the cut-off seal and the rotor.