Best Catted High-Flow Downpipe

Published in

Stone Exhaust USA

4 min readOct 6, 2021

Can’t decide whether to go catless or catted? Want that sound and performance boost but wish to stay road-friendly at the same time?

Over 2 decades in the industry, STONE has obtained 5 of its own patents.

The Arc-Fluid Eddy Catalytic Technology patent is a technology that outperforms conventional catalytic. With this, the goal is to increase horsepower while remaining environmentally- and road-friendly.

How does the Eddy Catalytic work?

Firstly, we know that stock downpipes come with a dense honeycomb structure made up of small passageways or cells which work by removing harmful chemicals from the exhaust gases. However, these passageways also strangle the overall exhaust flow, preventing the engine from producing more power and at a much slower rate as well. All cars come equipped with a higher cell count and the higher the cell count, the cleaner the emission but the more restrictive they are performance-wise.

An aftermarket catted downpipe however comes with a less restrictive catalytic converter with a reduced cell count and improved flow design than the stock downpipe, thus reducing exhaust back pressure and improving the exhaust flow by a margin whilst still producing acceptably clean emission.

And as a total opposite, a catless downpipe also known as a decat has no cells and therefore no exhaust gas cleaning properties. This leads to poor emissions which can cause you to fail road emission tests as well as throw off a funky smell due to the chemicals and soot which are usually filtered out by the catalytic converter that is no longer in place. A catless downpipe may be significantly cheaper than a catted downpipe, but it is not suitable for road use and is guaranteed to trigger the Check Engine Light (CEL). Even FIA events are required to have a sports catalyst fitted. Catless downpipes are therefore only suitable for off road or track use.

Overall, installing an aftermarket sports catalytic downpipe should support two key functions:

Provide the comfort of having clean emissions and remaining road-friendly
Bring a boost to your engine performance without having to worry about throwing a CEL

Unique Vortex Effect

With STONE downpipe’s unique vortex design, it is able to accomplish just that and more. The downpipe design comprises the Arc-Packaging method, leading to an end result of a vortex effect on turbine emissions. The vortex effect in turn allows the downpipe to purify exhaust gases more effectively compared to alternative methods used in the industry without sacrificing back-pressure.

Furthermore, with the vortex design, the air does not go straight through the pipe. Instead, it goes through in a circular motion which helps performance. Compared to OEM downpipes, STONE downpipe will give you higher torque at a lower rpm much quicker and more horsepower at a higher rpm.

>> For the full video of the Eddy Catalytic Technology, click here.

For years, STONE has focused their efforts largely on the performance of the engine and exhaust with special attention to creating an in-house technology that is not easily replicated because of its unique design and effect on performance gains. This patented Arc-Fluid Eddy Catalytic technology achieves the goal of increasing horsepower whilst remaining conscientious towards environmental impacts and general accessibility.

>> Check out this video of STONE downpipe installed on Mercedes-Benz CLA 250

Premium Quality Metal

STONE utilizes premium quality metals to construct these downpipes to improve the catalytic converter’s absorption of harmful micro particles which results in a faster and smoother flow.