A muffler is the American term for the device that removes noise from the exhaust system of an internal combustion engine. It is called “muffler” in British English. Silencers or mufflers are mounted within the exhaust system and have no primary exhaust function. They are made of sound-absorbing materials that reflect sound waves to cancel each other out. The exhaust system increases engine performance by manipulating pressure waves. It removes the exhaust gases leaving the cylinder and flowing into the pipe. It also controls the movement of the pressure wave produced by pressure spikes.
The muffler is an acoustic soundproofing device to reduce the sound of the engine through acoustic silencing. It consists of a set of chambers or pipes with some holes. A resonator is connected to the first chamber with a hole, and it contains a certain amount of air having a specific length capable of producing a wave that cancels a certain frequency of sound. When the exhaust valve opens creating pulses, there will be a sudden burst of high pressure gas entering the exhaust system. The high pressure gas molecules will start to collide with the low pressure molecules in the pipe, forcing them to stack on top of each other. As this happens, they build up in molecules a bit farther from the pipe. As a result, a low pressure field is created behind them, and the sound wave moves down the pipe, gaining more speed than the real gases. Exhaust gases and sound waves, entering the center pipe, bounce back and pass through the hole to the main body of the muffler. Upon reaching it, they go back through another set of holes in the next chamber to turn around and leave the last tube’s muffler.
The muffler can slow down the exhaust flow, making it harder for the engine to expel gas. This disadvantage of the muffler running on engine performance can be overcome by using sound absorbing glass mufflers. Such mufflers are designed in such a way that they do not restrict the flow of exhaust gases. The “Vector” muffler, the “spiral baffle” muffler and the “Aero turbine” muffler are other types of mufflers designed for optimal performance. However, some vehicle users replace the existing muffler with separate mufflers during engine tuning to increase power and reduce fuel consumption, which is illegal under existing Motor Vehicle Law.
An exhaust system is a set of pipes used to keep exhaust gases away from controlled combustion within the engine. The gas burned inside the engine is known as “exhaust”. The exhaust system has two operating components. The first component is related to the expulsion of exhaust gases from the cylinder. It occurs when a pulse of hot gas leaves the cylinder and moves away towards the primary tube of the collector. The second component is the movement of the pressure wave that takes on variations in the port when the exhaust valve opens. By manipulating these pressure waves that occur in the second component, the cylinder in the first component can be cleaned to allow fresh charge to enter.
When the exhaust valve opens in a four-stroke piston engine, the pressure in the cylinder will be above atmospheric pressure, and the valve pressure at the exhaust port is close to one bar (atmospheric). The rapidly changing pressure variation across the valve opening allows exhaust gases to flow through the opening, causing the pressure behind the valve at the port to rise rapidly. Since the velocity of the exhaust gas flow at any point is proportional to the pressure gradient and cross-sectional area at that point, a small variation in the header can increase the velocity at a given RPM. If the header diameter is too small, a loss of gas flow will occur, increasing the pressure gradient. This situation can lead to offset adjustment gains. Therefore, the selection of the diameters of the pipes is very relevant in the design of the exhaust system. The exhaust pipe must be designed in such a way that it carries toxic gases and other gases, such as hydrocarbons, carbon dioxide and nitrogen oxides, away from the user of the vehicle.