When discussing aftermarket performance mufflers, there are three types. The explanations below will help you choose which one is best for your Challenger:
Glasspack: A glasspack muffler is a straight-through, single tube design. There is a single tube inside the muffler, with perforations punched into the inside. The tube is surrounded on the outside with fiberglass mat packing. The outer shell wraps around the outside of the fiberglass packing. This design allows exhaust gases to flow straight through and out of the muffler.
Some of the sound penetrates the perforations and is absorbed by the fiberglass packing. Glasspack mufflers emit a very loud, high-pitched sound. They are typically the loudest type of street muffler.
Chambered: The chambered muffler is constructed with anywhere from 1 and 4 chambers on the inside of the outer shell. The exhaust enters the center chamber(s), and encounters baffle(s) on the inside.
The exhaust gases quickly flow through and out of the muffler while a portion of the sound waves are impeded by the baffles. Chambered mufflers are known for their deep, metallic tone. They are middle of the road as far as sound volume goes.
Turbo: The turbo muffler is constructed in a similar manner to a stock muffler. There is a metal outer shell, with 2 or 3 perforated tubes inside.
Unlike the S-shaped path of the stock muffler, the turbo muffler has a more circular flow path. Exhaust enters the muffler and gases escape through the perforations in the inner tubes. Sound is partially restricted by the tubes. This is easily the quietest design of aftermarket mufflers.