several embodiments of exhaust systems including reflective valve means interposed between the engine exhaust ports and an expansion chamber for improving performance at mid range and under low speeds . the reflective means comprise a plurality of rotatably supported members that are affixed to different shafts and the shafts are coupled together for simultaneous rotation . in some embodiments , the shafts are coupled by a linkage system and in another by means of a gear system . the shafts are journaled in either the same or separate valve housings and the valve members may be positioned on different horizontal planes or at an angle to each other to suit a variety of exhaust pipe configurations .