Upgrading your downpipes is one of the most impactful modifications you can make to a turbocharged vehicle. It’s often one of the first steps enthusiasts take when moving toward a Stage 2 setup, and for good reason. Few upgrades unlock as much power, sound, and responsiveness in a single change.
But once you start looking into downpipes, you’ll quickly run into the question: should you go with a catted or catless setup?
At a glance, the difference seems simple. One includes a catalytic converter, the other doesn’t. In reality, the decision is more nuanced. Your choice will affect not just power output, but also sound, drivability, and overall ownership experience. Understanding those differences is what allows you to build a setup that actually fits your goals.
Understanding the Role of a Downpipe
The downpipe connects directly to the turbocharger and routes exhaust gases into the rest of the exhaust system, as shown in this ARM MK8 Golf R 4″ Catless Downpipe above. From the factory, this component is heavily restricted due to emissions requirements, typically using dense catalytic converters that limit airflow. Couple a restrictive catalyst with a narrow diameter downpipe and you have a critical bottleneck in your exhaust system.
When you replace the factory downpipe with a performance version, you reduce that restriction significantly. The result is improved exhaust flow, quicker turbo spool, and noticeable gains in horsepower and torque. It also lays the foundation for further upgrades, making it one of the most important supporting mods in any performance build.
A catted downpipe retains a catalytic converter, but not the restrictive version found in OEM systems. Instead, it uses a high-flow design that allows exhaust gases to pass through more efficiently while still filtering emissions.
At ARM Motorsports, our catted downpipes utilize 200 cell high-flow sport catalytic converters as seen on the ARM N63 Catted Downpipes below, which strike a balance between performance and usability. Compared to factory units, these sport cats dramatically reduce restriction while still maintaining a level of refinement that makes the car far more livable day-to-day.
In practice, this means you still gain substantial performance improvements, but without many of the trade-offs that come with going fully catless. The exhaust note becomes deeper and more aggressive, yet remains controlled. Odor is significantly reduced compared to catless setups, and overall drivability stays closer to OEM+ rather than raw and unfiltered.
For most drivers, especially those using their car regularly, a properly designed catted downpipe delivers the performance increase they’re looking for without introducing unnecessary downsides.
What to Expect from a Catless Downpipe
A catless downpipe removes the catalytic converter entirely, allowing exhaust gases to exit the turbo with minimal resistance. This creates the least restrictive path possible, which is why catless setups are often associated with maximum performance.
With fewer obstructions in the exhaust stream, turbochargers can spool faster and operate more efficiently at higher power levels. The sound also becomes significantly more aggressive, louder, sharper, and more raw, especially under load as heard in this ARM MK7 4.5″ Catless Downpipe below.
However, that performance comes with trade-offs that can be hard to ignore for some people. Without a catalytic converter, exhaust odor can become much more noticeable, particularly at idle or in traffic. In addition, check engine lights are to be expected without proper tuning. It is also important to note that catless downpipes are intended for off-road use only and may not comply with emissions regulations depending on your location.
Catless downpipes tend to make the most sense in builds where performance is prioritized above all else, track-focused cars or aggressive setups where comfort and subtlety are not part of the equation.
Real World Performance Differences
When comparing catted and catless downpipes, the assumption is often that catless will deliver dramatically higher power. In reality, the gap is much smaller than most expect.
Both options significantly outperform the factory downpipe, and both unlock meaningful gains in horsepower and torque. A well-designed catted downpipe, especially one using a 200 cell high-flow catalytic converter, captures the majority of those gains while maintaining better overall drivability.
The difference between the two typically comes down to marginal increases. For most street-driven cars, that difference is rarely noticeable in day-to-day driving.
Sound and Driving Experience
Sound is one of the biggest deciding factors for many enthusiasts, and the good news is both catted and catless downpipes will increase the sound of your build.
Catted downpipes tend to produce a deeper, smoother tone that enhances the factory exhaust note without overwhelming it. When paired with additional upgrades like a midpipe, the sound becomes more pronounced while still remaining controlled.
Catless downpipes, on the other hand, push the system toward a much more aggressive profile. The exhaust becomes louder across the entire RPM range, with sharper notes and more pronounced turbo noise. For some, that rawness is exactly the goal. For others, it can become tiring over time. Many of our catless downpipes are resonated. A resonator is an unobstructed component that sits within the exhaust flow and is designed to shape the sound rather than restrict it. It helps deepen the exhaust tone and reduce unwanted rasp, while still maintaining the optimal performance characteristics of a catless setup, because, well, it is a catless setup as seen in our S55 3″ Resonated Downpipes below.
Check Engine Lights, Tuning, and Practical Considerations
Both catted and catless downpipes can trigger check engine lights due to changes in exhaust flow and sensor readings. That said, catted setups are generally less prone to this issue, especially when paired with proper tuning.
Catless setups almost always require tuning to avoid the ever-unwanted check engine light. This is an important factor to consider when planning your build, as it adds another layer to the upgrade process. While a CEL can be annoying to look at, it will generally not effect your car from running optimally or benefitting from a downpipe upgrade.
Choosing the Right Setup for Your Build
There isn’t a one-size-fits-all answer, but there is a clear way to think about the decision.
If your goal is to build a fast, responsive car that you can enjoy every day without dealing with excessive smell or harshness, a catted downpipe, especially one using a high-quality 200 cell sport cat, is typically the best choice. It delivers strong performance gains while maintaining a level of refinement that makes the car feel complete. However, this does come with a price, as the catted versions are typically 25-50% more than their catless counterparts.
If your focus is purely on maximizing output and creating the most aggressive setup possible while saving a few bucks, a catless downpipe is likely the right choice for you.
If you were on the fence between catless and catted, we hope this article helped you decide which direction is best for your build, and if you want further input for your project send us an email and we’ll be glad to help you!