It is known that the performance of an automobile engine can be increased in many instances by providing a crossover connection between the exhaust pipes in the automobile's exhaust system to balance the instantaneous pressure between the two branches of the exhaust system. Consequently, various configurations of crossover pipes extending between two exhaust pipes have been developed and used, such as a length of pipe extending between exhaust pipes to form an H-Pipe exhaust assembly. A similar connection can be formed by bending the exhaust pipes so that the exhaust pipes come together for a short distance in side-by-side relationship and then separate again. A hole is cut in the side of each of the two pipes where they come together and the pipes are joined, such as by welding around the mating holes, so that the interiors of the two pipes communicate through the hole. This type of connection is commonly called an X-Pipe connection since the pipes generally form an X shape where they come together. A connection where multiple exhaust pipes are connected to one end of a chamber or collector and two tailpipes are connected to the opposite end of the chamber or collector is shown in U.S. Pat. No. 4,953,342. These various cross flow regions described between the secondary exhaust pipes are designed to allow fluid communication or cross flow of the exhaust gasses from each of the headers of the engine prior to entering the tailpipes. Such cross flow communication is desirable for reducing peak pressures and the build up of exhaust gasses leading to excessive back pressure, and to allow for the more efficient discharge of exhaust gases. These arrangements can be used with one or two tailpipes as shown in U.S. Pat. Nos. 6,283,162 and 6,360,238. Further, similar results can be achieved when combining the exhaust flow from two exhaust pipes into a single exhaust or tailpipe to form a Y-Pipe exhaust assembly. U.S. Pat. No. 6,478,330 shows two exhaust pipes with beveled outlet portions affixed together along a respective edge of each thereof so as to merge together, with respective centerlines at an oblique angle, into a single outlet opening which is connectable to the inlet of a tailpipe.
Attempts have been made to combine the effects of the crossover exhaust systems with mufflers, wherein with the exhaust pipe crossover is located within a case which serves as a muffler. For example, the Dynomax Ultra Flo X muffler from Tenneco Automotive Operating Company Inc. of Lake Forest, Ill., has two exhaust pipes entering one end of a muffler case which come together in the center of the muffler case in an X-Pipe configuration and then extend out the opposite end of the muffler case. The exhaust pipes are perforated along their entire lengths within the muffler case and the muffler case includes packing, such as fiber glass packing, to provide noise absorption. Goerlich's, Inc. dba XLerator Performance Exhaust of Goldsboro, N.C., sells an X Muffler which includes an X manifold within a muffler case with two exhaust pipes entering one end of the manifold through one end of the muffler case and two exhaust pipes leaving the other end through the opposite end of the muffler case. The X manifold within the muffler case brings the exhaust from each exhaust pipe together in the center of the manifold as in the X-Pipe configuration. Again, the X manifold is perforated around both the inlet end and the outlet end to allow exhaust gas flow into the muffler case throughout its entire length. U.S. Pat. Nos. 6,589,499 and 7,326,950 show similar mufflers. All of these mufflers claim to provide the performance advantages of an X-Pipe exhaust crossover while at the same time providing a muffler for exhaust noise reduction. However, the Inventors of the performance-enhancing crossover muffler described herein have found that these types of mufflers do not provide the same level of performance increase that is provided by an optimized crossover exhaust system.