Topics:
Exhaust:
The exhaust facilitates the expulsion of exhaust gases produced during engine combustion. It is attached to the engine block.
As the exhaust gases exit the cylinder, they go directly through the exhaust manifold (sometimes via a turbocharger) into the exhaust system. The purpose of the exhaust is to expel the gases out behind the vehicle. If the exhaust were to terminate under the vehicle, the gases (which are harmful to health) could easily enter the interior.
The exhaust typically consists of an exhaust manifold, a catalytic converter, a flexible part, a middle muffler, and a rear muffler (commonly referred to as a “cherry bomb” in colloquial terms). These components are discussed below.
Flexible Part:
The engine produces many vibrations. The flexible part (see image below) dampens these vibrations so that the rest of the exhaust remains as free of vibrations as possible. Otherwise, there is a high chance that parts such as the exhaust manifold and the exhaust connections will crack and break over time.
The flexible part is mounted closely behind the exhaust manifold. Sometimes the catalytic converter is mounted directly after the exhaust manifold to warm up as quickly as possible (as shown in the image), while in other vehicles, the catalytic converter is located after the flexible part.
Exhaust Muffler:
The primary function of an exhaust muffler is to reduce the sound produced during engine fuel combustion. Sound is generated by air vibrations caused by the rapid exhaust gases exiting the engine cylinders. Each power stroke generates a pressure wave that causes air vibrations in the exhaust, resulting in a high-frequency noise. The exhaust muffler is designed to dampen these sound waves and attenuate the vibrations, making the engine noise less intrusive.
A muffler usually consists of several metal tubes nested within each other, featuring holes or slots that partially redirect the airflow. The air must travel through a series of bends and chambers where the sound is absorbed or redirected, dampening the sound vibrations. Heat-resistant damping wool (usually fiberglass or metal fiber) often surrounds the tubes, further absorbing the sound frequencies.
Sound reduction is not only achieved by slowing the airflow but also by sound wave interference within the muffler. There are so-called speaker effects in the muffler where sound waves counteract each other at certain points through acoustic interference. This process effectively attenuates both low and high frequencies of the exhaust noise.
An exhaust muffler is often composed of a front and a rear muffler.
The rear muffler, often the most common type, serves as the final line of sound reduction and is located at the end of the exhaust system, just before the tailpipe. It is capable of reducing most of the remaining sound waves, bringing the overall noise level to an acceptable standard.