The catalytic converter and muffler operate to dampen sounds and control vehicle emissions. Some states require that all vehicles manufactured after a certain date have both. Increasing the noise level of your exhaust on newer vehicles requires purchasing aftermarket exhaust systems. Older vehicles, such as a 1960s era truck, are grandfathered in, allowing for the use of straight piping. You can modify the exhaust on an older vehicle easily without having to buy any expensive parts.
Cut the exhaust pipe with an angle grinder where the exhaust pipe meets the muffler coming out of the engine.
Cut the hangers on the disconnected pipe with the angle grinder and remove the excess pipe. You will see two to three hangers connecting the pipe and the frame extending towards the rear of the vehicle. Cut all of them.
Drill three holes near the tip of the remaining pipe along the bottom edge. The holes will cause some reverberation, increasing the noise level.
Some states require that piping extend to the rear or sides of the vehicle. You can have straight pipe installed by a professional for a very low price, typically under £32.
Leaving the pipe at the midsection of the car points the exhaust at the rear axle, which could lead to possible damage to the suspension, brakes or brake lines. You should run the pipe to the rear or side of the vehicle as opposed to leaving the exhaust port centred beneath the vehicle. Leaving the pipe centred for a short period of time should not damage any systems beneath the car.