Introducing the APR Catback Exhaust System for the Audi B9 S4 and S5! The APR Catback Exhaust System for the Audi B9 S4 and S5 is a complete, high-performance exhaust solution that runs the entire length of the vehicle from the catalyst back. Inspired by the larger center-pipe design of the higher-output RS4 and RS5 models, this system is engineered to boost performance, elevate sound, and enhance aesthetics with customizable exhaust tips that are sure to make a statement. Crafted from premium materials and built with advanced manufacturing techniques, this system is designed to withstand harsh conditions and deliver lasting performance. Expect a bold, aggressive growl at wide-open throttle, along with an impressive gain of 10 horsepower and 12 FT-LBS of torque to all four wheels!
Unlike anything currently available, the APR system includes downpipes extending to the factory catalyst in the upper engine bay, making this a true full-system upgrade. We’ve minimized restrictions with smooth transitions, oversized piping, and straight-through mufflers and resonators. Constructed from mandrel-bent T304 stainless steel with a brushed finish and TIG welding throughout, this exhaust system is as durable as it is striking. Installation is hassle-free, thanks to precision-fit brackets, OEM-style slip clamps, and an included upgraded tunnel brace to accommodate the oversized piping.
Like the RS4 and RS5, this system features a reengineered exhaust routing design. It utilizes dual 2.5” (63.5mm) downpipes to dual 2.75” (70mm) midpipes pipes merging through a cast Y-junction into a massive 3.5” (91mm) midpipe, replacing the restrictive factory dual-pipe setup. The integrated Helmholtz resonator minimizes drone through a straight-through design with a sound-canceling port, ensuring no compromise in exhaust flow.
The system splits again via another cast Y into two rear, valve-controlled mufflers with sound absorption technology. These valves are fully integrated with the OEM control system, adjusting automatically to enhance sound during aggressive driving while maintaining a quieter profile during cruising. Finally, exhaust gases exit through dual cast Y-junctions into a quad 2.5” (63.5mm) system, terminating in 3.5” (91mm) lightweight, single-walled motorsport-style tips. The tips feature a polished stainless steel finish and a subtle APR logo for a refined touch.
Designed for enthusiasts seeking the perfect balance of power, sound, style, and quality, the APR Catback Exhaust System for the Audi B9 S4 and S5 is a testament to engineering excellence. With its performance-driven design and durable construction, this system not only transforms your driving experience but also ensures years of reliable performance.
Features:
- Complete catalyst-back system including downpipes, extending from the factory catalyst back
- Performance gains of 10 HP and 12 FT-LBS of torque delivered to all four wheels
- Premium T304 stainless steel construction with TIG welding for strength and durability
- Optimized flow through dual 2.5” downpipes, 2.75” midpipes, and a 3.5” midpipe
- Mandrel-bent brushed piping paired with electropolished cast splitters for a refined finish
- Precision brackets and slip clamps ensure accurate alignment and hassle-free installation
- Includes an upgraded tunnel brace to accommodate the larger piping
- Integrated Helmholtz resonator minimizes drone and enhances sound quality
- Valve-controlled rear mufflers dynamically adjust sound based on driving style
- Removable quad 3.5” motorsport-style polished tips with APR logo; optional styles available
- Smooth transitions and straight-through components maximize performance by reducing restrictions
- Strikes the perfect balance of power, sound, style, and quality for enthusiasts
- Fully emissions compliant for worry-free operation.
What's Included:
- APR Catback Exhaust System
- Installation hardware
