Choosing the Right Downpipe for Turbocharged Car Upgrades

Decats, straight pipes, race cats, E-cats… an eager car enthusiast might feel overwhelmed – how do you decide the best option for your car upgrades?

As you may know, in a turbocharged car, the first meter of the exhaust system is critically important for optimal exhaust flow and performance. Exhaust gases are at their hottest when leaving the turbo, requiring the maximum flow capacity from the pipe for everything to function efficiently.

When upgrading your car’s exhaust, there are plenty of options – and not all of them are legal for road use! Here, we’ll go over the different types of downpipes, their benefits, and the most important selection criteria.

Different Types of Downpipes

1. Racing Downpipes (Decats, without catalytic converter)

Racing downpipes are straight pipes that replace the catalytic converter. They provide maximum exhaust gas flow and a much rawer, sportier sound compared to stock exhaust – which is something to keep in mind. Catalytic converters are efficient sound mufflers, and the larger and denser the catalytic core, the quieter the exhaust. A straight pipe produces a significantly rougher exhaust note.

In diesel vehicles, this type of downpipe typically replaces both the cat and the DPF filter (which is a legally required component for road use).

Note: If you’re planning to use pops & bangs, crackle, or burble features, downpipes with cats are not ideal since the lifespan of the cat is significantly reduced.

2. Downpipes with High-Flow Racing Catalytic Converters

Models with racing cats are popular and typically feature a 200CPI (cells per inch) metallic catalytic core. Depending on the manufacturer, these are available in Euro3, 4, 5, or 6 emission standards, with varying filtration capabilities and precious metal content.

This option offers a great balance between performance and emissions control. In a well-maintained engine, these cats usually pass standard emission tests and reduce exhaust odors. However, they are NOT fully ECE-certified, which could cause issues during inspections depending on regulations and market areas. For example, in Finland, ECE certification is officially mandatory for modern cars.

You’ll find such downpipes in our selection from brands like Milltek, RM Motors, F* Essentials, Supersprint, HJS, Bull-X / HG Motorsports, and Wagner Tuning.

Example of a racing catted downpipe:
Audi/Volkswagen/Seat/Skoda
MQB AWD EA888.3 RM Motors 200CPI downpipe

3. Fully ECE-Certified Downpipe – Safe and Legal

The fully legal and worry-free option is an ECE-certified downpipe specifically designed for your car. This is the only option that can be used fully legally on public roads.

These downpipes feature high-quality, high-flow catalytic cores with significant precious metal content and come with model-specific European certification to ensure compliance with regulations.

This option provides improved flow, performance benefits, a slightly sportier sound, and proper emissions filtration.

The downside? As expected, these are significantly more expensive than the other options.

We offer ECE-certified downpipes from brands like HG Motorsport, Bull-X, HJS, Milltek, and Supersprint. Note that only a selection of these options is listed online – contact us for tailored solutions for your car through our Contact Us page!

Using the earlier VW Golf example:
VAQ MQB EA888.3 AWD ECE-Certified Bull-X Downpipe

Other Considerations When Choosing a Downpipe

What About The Sound?

Catalytic converters and particulate filters (OPF, GPF, DPF) are highly effective sound dampeners, so upgrading your downpipe significantly affects your car’s sound profile.

Sport cats have a less dense and often shorter core, resulting in a slightly sportier tone than stock, but still moderate.

With a straight decat pipe, the noise can become significantly louder and rougher depending on the car.

Sound Amplification in OPF Models

This effect is even more pronounced in modern cars equipped with OPFs, where the stock exhaust is more open to compensate for the particulate filter. Replacing the cat/OPF in these vehicles can dramatically increase sound levels.

BEWARE: Low-Quality Cheap Catalytic Converters

Not all racing catalytic converters are created equal.

The cheapest options found in online markets may lack essential active metals (like platinum, palladium, or rhodium) necessary for emissions cleaning. These so-called “racing cats” essentially function as expensive resonators without any real effect on emissions.

Choose the Right Model for Your Needs

The choice depends on your performance goals, local regulations, and personal preferences. Are you building a track car or just sprucing up your daily driver?

Explore our selection in the DOWNPIPES category and check out examples for your car!

Downpipe with installation by professionals

We also offer turn-key installation at our Vantaa location, professionally and at a fair price.