- 1). Create a perforated inner stainless steel pipe from sheet metal, wrap it with a two-layer course and medium stainless steel wool system and weld the ends to the outer metal casing. Put a slight S bend into the inner tube to reduce the drone inside the car and overall noise coming from the exhaust. Remember, high-performance mufflers do not sacrifice engine output in the name of sound deadening, according to Exhaust Videos.
- 2). Buy or make a perforated metal pipe by taking a piece of perforated sheet metal and bending it into a long tube using your hands and a rubber mallet. Aim to create a tube about 20 inches long with an internal diameter of 1.5 inches, although the exact dimensions will depend on your car. FH Bundle, for example, offers a range of sheet metals with perforations. The hole size is irrelevant, but the thickness should be above 1 mm.
- 3). Create a set of two seven-degree angles along the length of the perforated metal pipe using a mallet. Aim to achieve a very slight S shape in the pipe. Measure the angle using a trial and error method with a protractor. If the pipe is not bent enough, add extra curvature by hitting it gently with the mallet. Bend the pipe to reduce the noise made by the exhaust.
- 4). Wrap course stainless steel wool number 3 around the length of the perforated metal pipe, making sure you create a layer about 1-inch thick. Use around 10 pads of the wool to create two, well-meshed layers. The course wool prevents overheating and fiber destruction. According to Piwel, stainless steel wool can withstand temperatures of 700 degrees Celsius. Wrap the course wool with paper tape.
- 5). Wrap over the paper tape with medium stainless steel wool number 1 to a thickness of about 1 inch. Increase the thickness depending on the size of the muffler steel tubing. The wool-wrapped pipe needs to fit tightly inside the steel tubing.
- 6). Push the wool-wrapped perforated pipe inside a similar length (20 inches) piece of steel tubing. The ends (not perforated) of the pipe should stick out at either end of the steel tubing. You should notice that the whole design now looks more like a standard car muffler.
- 7). Wear safety goggles, gloves and protective clothing. Weld the ends of the inner pipe to the edge of the outer tubing using a welder and two circular metal plates of sufficient size (about 2 inches in diameter should be enough). Allow the metal to cool.
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