Aftermarket Exhaust Buying Guide

Posted by Willem Fisher on

Understanding Aftermarket exhaust systems.

Okay, it sounds like a simple thing to upgrade your exhaust system but let's be honest, with everything from different exhaust tips, multiple brands, like Milltek exhaust, Scorpion exhaust, then the option of a custom exhaust it is a minefield. This is before we get into a non-resonated vs resonated debate!

In this guide, you will find all the information required to make a stellar purchase on your next car exhaust, with an easy to understand newbie friendly exhaust system buying guide.

Non-resonated Vs Resonated cat-back exhaust.


This is a question we are regularly asked in the shop. The answer is fairly linear on this one, and it's all down to the customer preference, type of vehicle, and engine.

For example, some of the later turbocharged vehicles, such Golf R, Fiesta ST, Yaris GR etc, are turbocharged from the factory and even carry a GPF and so the sound is very much muffled by the turbo, catalytic converter, and in some cases the GPF. In most of these cases, a non-resonated exhaust is almost definitely the one for you.

Non-Resonated Exhaust:-

Consistent with its title, this exhaust system will remove all resonators used to quiet a system down but will retain the backbox. This will offer a louder, more distinctive tone, especially on cars using an upgraded downpipe, such as a high flow sports cat or large bore downpipe, also known as a decat. This denotes a turbo-back exhaust system as a turbo-back exhaust replaces the entire system from the turbo to the exhaust tips.

The non-resonated cat-back exhaust system also offers some weight improvements by changing the resonator to a straight pipe, and in some cases, this will help marginally with the airflow, especially on the larger diameter products over an original exhaust.

Resonated Exhaust System:-

In contrast to its non-resonated counterpart, the resonated system is the perfect option for a user looking to be seen and not immediately heard. It has all the looks and hallmarks of an upgrade with a very subtle uplift in volume, and in some cases almost underwhelming. Retaining a resonator in the rear link pipe and a back box, this system will suit someone who requires less cabin drone and a more subtle exhaust note.

Valved Vs Non-Valved:-

For us, this is a big one. It does exactly what it says on the tin, either retaining the factory fitted valves for quieting the exhaust down or providing an aftermarket valve, allowing operation during use to increase and decrease noise.

We personally believe that having the option to open and shut the valves is the best of all worlds for upgrading your performance car. In this instance, a customer who is leaning toward a quieter, resonated system can opt for a mix of subtle tones when on a subdued weekday drive to the office, and with the flick of a switch open the valves, listen to your engine notes rise to engage with the wheel and enjoy the B-road blast that you originally bought a sports car for.

In short, this option would allow a user to run a non-resonated system with a valved option, to keep it quiet during day-to-day driving but increase noi

se with an open valve when desired by the driver.

Lots of today's performance cars come with this option on the OEM system, such as BMW M135/M140i Golf R/Audi S3 and almost all of the upper end of the sports car range. This means, in many cases, you retain the factory valves as an option on your aftermarket system.


Difference in Brands:-

So you have concluded which of the above options is for you, now you need to know which of the brands or indeed if a custom exhaust system is for you. In this section of our handy exhaust-buying guide, we will outline all of the sounds from each individual brand.

Milltek Sport Exhaust:-

Steeped in history, Milltek Sport has been one of the go-to companies for all things related to exhausts. Made in Derby, United Kingdom, they have featured in multiple brands race series and supercar OEM products. Made from stainless steel and wielding a lifetime guarantee, it's clear for all to see why this brand is so popular. You will not be disappointed with a Milltek exhaust system!

Key Notes:-

  • High grade stainless with a lifetime guarantee
  • Manufactured in the UK
  • Most distinctive non resonated option (very good low drone levels in cabin)
  • Resonated marginally louder than stock more for aesthetics
  • Available with multiple tip options inc carbon

Scorpion Exhaust System:-

Scorpion exhausts are not only a big name in cars but have a huge reputation in performance motorcycles. The CEO, Shaun Leonard, started out as a machinist and engineer so, you can guarantee the highest quality every single time. Based just up the road from Milltek Sport, just outside Ripley Derbyshire, it's incredible to think these guys are so close yet produce the same products and ship worldwide. It's true to say we have some of the best manufacturing and engineering in the world right here in the UK.

Scorpion has some of the finest engineering facilities we have seen and a multitude of skill sets from design to production, and certainly an impressive dyno testing facility to develop their product range.

Key Notes:-

  • The UK designed and Manufactured
  • High-grade stainless steel
  • Non-resonated deeper tone (slightly more cabin drone)
  • Resonated marginally louder than OEM system
  • Multiple tip options (new carbon option looks great.)

Cobra Exhaust:-

Cobra Exhaust is possibly the most versatile manufacturers we have used. Born out of a custom services stainless steel exhaust manufacturer, catering for any make and model, they can manufacture anything from a custom-built stainless system to a hundred off production order.

Based in one of the Norths most recognised manufacturing locations, Steel City aka Sheffield. They have over 50 years in the business so it's safe to say they know a thing or two.

Key Notes:-

  • From Prototype to production in the UK
  • Lifetime Guarantee and high grade stainless
  • Loudest of the exhaust options, in our opinion. If you want to be heard these are the go-to product
  • Amazing amount of exhaust tip options

Remus Exhaust:-

Having visited the Remus factories (yes both OEM and aftermarket have a factory each), it goes without saying this is the biggest and most impressive manufacturing facility we have seen, and as it should it perfectly reflects in the quality and price of the Remus exhaust system range.

The Remus range of systems is well situated between the price of an Akrapovic exhaust system and the aforementioned UK made products. Meaning its high quality is justified, with a middle ground price point.

They have ties with the DTM championship multiple touring car series and many bike championships.

Key Notes:-

  • Large OEM supplier
  • Very high-quality systems to compete with Akrapovic Quicksilver etc
  • Distinctive tone system (non resonated would be our option here)
  • Huge testing facility from exhaust gases analyzed to dyno in the sound chamber

Custom Exhaust System:-

We see an awful lot of custom systems produced right here in the UK, from Powerflow agents to shops offering a custom service. Whilst not all of them are bad, we have seen some horrors, and more often than not, people assume that a custom exhaust is better than an off the shelf developed product. We can assure you this is absolutely not the case!

Unless you have a big enough budget to visit a shop that is willing to look at bend angles, diameter, the material used, back purging and much more, then you are unlikely to get a product suited to the type of vehicle you own.

A larger diameter stainless steel pipe is usually the way to go, but in our experience, using the correct size over the biggest that fits is what creates a great tone and overall performance benefit. All too often we see a 3-inch custom exhaust that has been downsized using a welded adapter to the stock size pipework which causes a huge mid system restriction.

Bending is often noted as too tight or harsh, and exhaust tips are usually welded so cannot be interchangeable.

There are some acceptable custom options, and we often get asked things like what is a back box delete? A back box delete is an upgrade that can often be a brilliant cost-effective exhaust upgrade where the backbox of your system is cut out, and the exhaust tips are welded directly to the pipework. This gives a good amount of noise increase, saves a little weight but unfortunately has no performance benefit.


What is a sports cat?

A sports cat is the upgrade from a standard catalytic converter which has generally a 200 cell internal honeycomb to replicate the OEM catalytic converter. This holds all the benefits of a cat but with much better flow properties to increase exhaust gas flow when you remap the car to a stage 2 remap. It is worth noting without a software remap the engine management light will most likely be present when you fit one of these.

A sports cat is the legal way to improve performance whilst passing the UK MOT test.

What is a decat downpipe?

A decat downpipe is essentially a complete removal of the catalytic converter found on your performance vehicle and replacing it with a piece of pipe. Guided for motorsport use only due to not passing the UK MOT and with the risk of VOSA spot checks, this product will give the best flow and is more cost-effective than a sports cat. You will require a stage 2 remap to work with a decat otherwise you will experience an engine management light.


Contact Us?

If you would like to speak to a member of our team to talk about what exhaust systems we offer or any other performance tuning hardware and software you may need you can contact us via our contact page.

Want to ring us?

You can contact us via phone call between the hours of 9:30-12:30 then 13:00-17:00 Monday to Friday.

Phone Number: 01924 228042


1 comment

  • Good informative blog !

    james Pearman on

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