In order to achieve very high thermal efficiency, we developed a prototype engine for aerospace based on a new combustion principle due to colliding pulsed supermulti-jets. The prototype engine has ignition assisting system called “torch system” to stabilize startup. The previous torch system has a problem that ignition is unstable. In the present report, ignitability of torch system is improved by changing gas for combustion in torch from air to oxygen. Emphasis is placed on the fact that air-insulation effect on the side-wall in the new strong torch system occurred. This will occur, because weakly-pulsed pressure wave generated around the torch center hits the side wall, which reflects and pushes back the burned gas toward the chamber center. The result of the experiment indicates a possibility of air-insulation based on weakly-pulsated combustion at around center of combustion chamber “without the supermulti-jets colliding”. The new engine concept may improve thermal efficiency of conventional engines such as those of jet engines and piston engines, although the engine concept based on the supermulti-jets colliding with strong pulse proposed previously by us will bring higher thermal efficiency because of addition of silent high compression.