Abstract: An exhaust apparatus for internal combustion engines comprises an outer pipe having an enlarged intermediate portion and at least one end portion having nearly the same diameter as the exhaust pipe from the engine for connection thereto, an inner pipe of approximately the same diameter as the exhaust pipe, a plurality of helical passages provided between the inner and outer pipes and sets of fins arranged inside the inner pipe at each end to impart vortical flow of gases passing through the inner pipe and to accelerate the gases through the helical passages and absorb them from the engine, the end portion of the outer pipe being connected with the exhaust pipe by means of an encircling clamping ring.