A loud exhaust system is almost always a good thing. Almost. Favoured by enthusiasts, and the local riff-raff, loud exhaust notes are a hallmark of performance vehicles. But even the most grown-up astute driver with a little bit of a mean streak can’t deny the joy of owning a car with a loud exhaust. But what exactly is an aftermarket exhaust system? What goes into building a custom exhaust? And are such custom systems legal in Singapore?
First off, to understand how exhausts systems work, we have to delve into what they do. Simply put, they divert exhaust gases away from the driver and passengers. They also reduce the number of harmful emissions that can potentially harm the environment.
Aftermarket exhausts generally reduce the amount of back pressure by way of wider diameter pipes, thereby improving the engine’s power output and increasing the volume of the sound. The basic principle is: The less back pressure in the pipes, the more power you get, and the better the sound.
The core parts of an exhaust are the headers (or exhaust manifold), an oxygen sensor, the catalytic converter, the muffler, resonator, and the tailpipes. The headers are usually kept stock, except in the case of high performance race vehicles.
Right after the headers is the catalytic converter. And this is a neat piece of kit. A Catalytic Converter is an integral part of the exhaust system and it reduces the number of pollutants exiting the engine. Some systems include multiple oxygen sensors along the system to measure the exhaust gas and oxygen ratio to determine of the engine is running too rich or lean, as well as determine if the catalytic converter is working properly. It’s all chemical wizardry and technological know-how that would probably require a master’s or a doctorate to fully understand.
However, some cat-converter systems may inhibit the air flow coming out of the engine if they are poorly designed or clogged. This leads me to the next option tuners and some enthusiasts opt for. First of which are catback exhaust systems. Catback systems just refer to exhaust systems that have been designed to fit after the cat-converters. These are usually bolt on kits that can be fitted via an extension pipe or flanges, and generally do not affect the engine emissions drastically. In some instances, they even improve the flow of gases passing through the catalytic converter.
And then, there are De-Cat (or cat-less) exhausts. These de-cat systems eliminate the catalytic converter in the exhaust to reduce back pressure that could be built up and boost power further. But such systems have no way to regulate the harmful pollutants coming out the back of the car, making them highly illegal.
Another integral part of the exhaust system are the mufflers, which basically muffle the sound produced by the engine. Mufflers are an acoustic device with internal pipes and baffles that bounce the sound waves off the insides of the muffler housing, basically breaking up the sound waves to reduce the overall volume of the exiting gases. Some mufflers have baffle tubes with many holes drilled into them and fiberglass insulation to dampen the sound waves as the exhaust gases pass through the muffler. Think of it as a suppressor on a pistol.
Most modern cars come fitted with a resonator as well, and they can be located before or after the muffler. These further suppress the sound and drone emitted so whatever comes out of your tailpipe is less obnoxiously loud. Or in some cases (especially so in performance cars), it even enhances the sound by harmonizing with the muffler to produce a better exhaust note. High performance resonators can even offer performance benefits for the vehicle by minimising friction and back pressure to improve air flow.
And finally, the tailpipes. Well, these are pretty self-explanatory, they are the tail end of the whole system. And oftentimes, the only visible bit of the exhaust. These are usually tucked out of sight on some family sedans and MPVs, but some cars may have a chrome finishing tip to enhance the overall look of the car. Performance vehicles are usually fitted with wide, nicely trimmed tailpipes as standard. Mercedes AMG, BMW M, and Audi RS vehicles for instance.
Now there are two routes to go down in the pursuit of power and noise. Custom exhaust systems, and aftermarket exhausts. Custom jobs are generally cheaper. And depending on the skill of the workshop involved, the craftsmanship and welding can range from stellar to subpar. Some drivers may even venture into illegal setups that are extremely loud.
However, they stand the risk of getting caught by any passing traffic police officer with a keen ear. In Singapore, catalytic converters and mufflers are a legal requirement in vehicle exhaust systems, making de-cat systems illegal. Custom exhaust mufflers are also subject to these checks, and they are unikely to be cleared for road use. Changes to the exhaust pipe’s dimensions may also adversely hinder the performance of the vehicle.
Alternatively, one could go down the route of having an aftermarket kit installed. There are a wide range of exhaust systems available in various exotic materials such as carbon, ceramic or titanium. These kits often give a slight power boost and aid weight reduction for better performance. And there is a list of aftermarket exhaust systems that are approved by the LTA for use in Singapore. These systems require certification from the manufacturers that the system is suitable for the make and model of the car in question. The systems also have to comply with stringent noise level and emissions regulations in order to be classified legal for road use.
Given that these systems are made by aftermarket companies that specialise in well designed engine parts (HKS, Akrapovi?, Remus to name a few), it may be the better option for buyers. Not to mention legal. Even though they cost more, they are undoubtedly the better and safer option for drivers out there.