Stock exhausts are adequate at most. Sure, they’ll comply with current emissions and noise levels, and last up to the warranty, but to keep costs down, too many compromises are being made along the way. Carmakers use exhausts of smaller diameters and simpler designs, meaning less material, produced cheaply. By doing so, they hinder the potential of the engine which has to battle against more backpressure in smaller pipes. Aftermarket exhausts are a sure and tried solution to gaining a few extra horses, while also improving the exhaust note. They’re designed within regulations, but use bigger pipes of strengthened materials and better tubing techniques to get the most of what the engine has on offer.
Aftermarket Exhausts – The Materials
Stock exhausts are made of cheaper grades of steel that will degrade in quality over time. Rust is the main issue, along with questionable tensile strength leading to deformity and damage. Aftermarket exhausts don’t skimp on materials – the cheaper options with aluminised steel round the muffler will upgrade durability and are miles ahead over your stock exhaust both in performance gains and general wear and tear. For the best results, go for complete exhausts made of treated stainless steel which will prolong exhaust lifetime and withstand structural damage often inflicted by corrosion, excessive heat or physical impact. Stainless steel pipes are also coated or treated with chrome, giving your vehicle a much better look. Stainless steel exhausts may cost a few pennies more, but will save you money in the long run.
Aftermarket Exhausts – Types
Depending on whether you’re upgrading the whole exhaust, from the header down, or from a particular part, there are different kinds of aftermarket exhausts you can buy. For diesel vehicles, this also includes the particulate filter.
Axle-back exhausts are the most common modifications made to exhausts, and the cheapest, considering they replace the least number of parts. They include all the components from the rear axle to the exhaust tip, or the muffler, the tailpipe extension, the tailpipe and tip. Axle-back exhausts are the easiest to fit and take the least amount of time. An aftermarket axle-back will provide some gains in terms of performance, exhaust flow and sound over the stock exhaust.
Cat-back exhausts replace components from the catalytic converter. This includes the extension pipe, muffler, tailpipe extension, tailpipe and exhaust tip. Often a modified mid-pipe will be thrown in the mix. Cat-back exhausts offer increases in exhaust flow, meaning hotter gas travels faster due to larger pipe diameters, while not impeding on the purpose of the catalytic converter. Emissions remain within legal guidelines. Faster exhaust flow means more rumble and a faster vehicle.
These are found on diesel vehicles, with the exhaust parts replaced up to the diesel particle filter. This means that connecting pipes from the filter, intermediate and tailpipes are replaced. DPF-back exhausts help improve the work of the diesel filter by maintaining higher temperatures to burn up toxic diesel particles, particularly nitrous oxides. The result means lower emissions, useful for older vehicles that don’t qualify for the new standards. Like other exhausts, DPF-back variants also improve on exhaust sound and contribute to performance gains, particularly in torque output.
Header or turbo-back exhausts replace the complete stock exhaust from the header or turbo pipes, all the way down to the exhaust tip. The parts will include pipes that are wider and thicker, but designed to fit the underbody recesses, meaning no additional drilling or modifications. Larger pipes open up the exhaust to provide even gas flow throughout, reducing backpressure in every section. The performance gains are the highest in header-back exhaust systems, the exhaust sound is the deepest, and the emission of toxic particles is the least. Because of all the parts that need replacing and fitting, this is also the most expensive type of exhaust and requires the most work and time to fit.
Single vs Dual Exhausts
Most exhausts sold aftermarket are single exhausts replacing the stock type on your vehicle. I discussed the advantages and the variants available. A common type of axle-back single exhaust is the dual-tip exhaust, with twin tail exhaust pipes extending from the muffler. These are commonly found on stock performance vehicles. For your car, there isn’t a significant increase in performance over the basic axle-back exhaust, but definitely looks better. Larger vehicles, generally V6 and V8 petrols and diesels may have a dual exhaust setup, featuring two separate systems, coupled with modified midsections to handle uneven exhaust flow and back pressure from differing cylinder firing and combustion times.
Buying and Installing Aftermarket Exhausts
All types of aftermarket exhausts are sold by tuning specialists and retailers. Some stores only sell specific exhaust types, mostly axle-back exhausts, while others stock all variants. All stores will advise you on the appropriate exhaust for your particular model and make. Variants may vary across different MY of the same make and vehicle series, so get the right info. Stainless steel exhausts will be more expensive to buy and install than aluminised steel exhausts. You can install the exhaust by yourself if you’re mechanically inclined, or get it done professionally. All exhausts include the required bolts and brackets.