US Patent 7708114 Sound-attenuating muffler having reduced back pressure

The present invention relates to an improvement muffler that includes an improved inlet configuration having first and second sequential chambers with a perforated central pipe passing longitudinally through a central region of both chambers for directing the exhaust gases into the third chamber in which the deflection element is deployed. Additionally, the partition separating the first and second chamber has a hole that enables some of the gas to pass from the first chamber into the second chamber not through the central pipe.