There are as many different theories and designs of mufflers as there are companies making them. The science of muffler design revolves around three major areas: 1) sound, 2) flow, 3) and durability. For the team at Billy Boat Exhaust, we have taken our 25 years of experience, our racing background, and our practical approach to design a product that has a signature tone and provides a lifetime of driving enjoyment.
There are two basic ways to muffle an internal combustion engine. First, through absorption, in which the sounds waves are absorbed through a perforated core into some kind of packing material, and second, reflection, in which the sound waves are bounced off an internal baffle or back at each other in order to cancel the sound waves. We have built thousands of exhaust systems over the years and have found that each design theory has strengths and weaknesses. Our goal when we prototype a new exhaust is to create a deeper, throatier tone for the exhaust, increase the volume at idle and while under acceleration, but keep the interior volume quiet while at cruise and free of any “drone”. In order to meet these criteria, we use a combination of each design style in our exhaust systems. We do not use “off the shelf” mufflers in our exhaust systems- each application is evaluated, and we build what is the optimal solution for each vehicle. This provides us with the opportunity to achieve the ultimate sound and performance.
While most muffler companies use a standard round tube design, Billy Boat Exhaust uses a square tube design. This tube design allows for more volume in the muffler tube and also allows for more perforated surface area inside the tube. More volume means better flow and less restriction, while the increased surface area means more perforated material to absorb sound waves. We also use perforated arrows inside the tubes to direct the exhaust flow in a lazy S pattern, helping to increase the efficiency of the absorption side of the muffler.
The packing material around these perforated square tubes is equally as important as the design, as different materials have different acoustic properties. These materials must be durable and provide a lifetime of enjoyment, yet also emit the deep tones which create our signature tone. We use two different types of packing materials in our mufflers, a stainless steel mesh material and an extremely high temperature ceramic material. The stainless steel mesh is wrapped around all muffler cores to add a layer of durability to each muffler, while the ceramic material is used as a blanket around the core or as a void fill inside the muffler chamber. The combination of these two materials is unique in the exhaust industry and is the foundation for our deep, throaty muscle car tone.
Each of the mufflers in a Billy Boat Exhaust system also has a reflection component to it. We use internal Helmholtz chambers in each muffler, which are dead-end tubes branched off of the main muffler core. The name comes from a device created in the 1850s by Hermann von Helmholtz, which he used to identify various frequencies and sound waves. As the exhaust flows by these tubes, pressure is reduced and the sound waves reflect back in the opposite direction. We use these internal tubes to reflect and cancel the high pitched sound waves which cause “drone” in the exhaust.
Durability is also an important component of each muffler. We use only 18 or 20 gauge 304 stainless steel for our muffler cases, and the muffler endplates are all 14 gauge 304 stainless steel. Each muffler is hand built according to exact design specifications for each application, and then either hand TIG welded or welded in our robotic welding cell. Our goal at Billy Boat Exhaust is to build the best performing, best sounding and highest quality exhaust systems on the market. Our manufacturing techniques and our signature tone is unique in the industry in order to provide our customers with a “moment of adrenaline and a lifetime of performance.”