The ARM Motorsports Catted Downpipe for the Audi B9/B9.5 S4 and S5 is engineered to deliver major performance gains while reducing emissions and unlocking a far more aggressive exhaust tone. Featuring a massive 6.5-inch 200-cell high-flow catalytic section, this downpipe dramatically improves exhaust flow, allowing the EA839 3.0T turbocharger to spool faster, build boost more efficiently, and produce more power throughout the rev range.

Replacing the OEM downpipe—which uses a restrictive 800-cell catalyst—this upgrade improves throttle response, mid-range punch, and overall engine efficiency. Even without tuning, the ARM Catted Downpipe provides noticeable gains, and when paired with performance software, the benefits increase significantly. The improved exhaust flow also enhances the exhaust note, especially when paired with the ARM 3" Midpipes, producing an exotic, deep tone that transforms the driving experience.

Designed as a direct-fit component, the downpipe features a CNC-machined turbo flange that mates perfectly with the OEM turbocharger or any hybrid turbo using an OEM-style connection. The 6.5-inch catted section tapers smoothly into a 3.5-inch Y-pipe, ending with midpipe flanges engineered to fit both ARM and OEM midpipes. The included gaskets and hardware ensure a secure and leak-free installation.

Together, the ARM B9 Catted Downpipe and ARM B9 Midpipes remove the largest airflow restrictions in the factory exhaust system—making them the ideal combination for any EA839 build seeking maximum performance and sound while retaining OEM valve control.

Fitment:

Fits Audi models equipped with the EA839 3.0T engine:

• Audi B9 S4 3.0T
• Audi B9.5 S4 3.0T
• Audi B9 S5 Coupe 3.0T
• Audi B9 S5 Sportback 3.0T
• Audi B9.5 S5 Coupe 3.0T
• Audi B9.5 S5 Sportback 3.0T