Please note, this is a pre-order item. The ETA for this B8/B8.5 Audi S4,S5 Catback Exhaust  is approximately June 19, 2026. All pre-order sales are final and cannot be canceled.

CAP Audi B8/B8.5 S4 Exhaust System – With Integrated Resonated Downpipes

The best sounding 3.0T exhaust in the world. Engineered for Sound. Built for Performance.

While many aftermarket exhaust systems for the Audi B8/B8.5 S4 deliver impressive sound when paired with factory catalytic converters, a common issue arises as those OEM cats begin to fail—often due to heat-related breakdown over time. As a result, many owners turn to catless test pipes, which unfortunately introduce excessive rasp, harshness, and unwanted exhaust tones when combined with most existing exhaust systems.

As the global leader in test pipe sales for the B8/B8.5 S4,S5 3.0T, CAP recognized the need for a purpose-built solution for vehicles equipped with catless test pipes. Since 2020, our team has been developing an exhaust system specifically engineered to work in harmony with catless test pipes. The focus was on eliminating unpleasant high-frequency tones and resonance, while maintaining optimal flow and performance.

The result is a cat-back exhaust system that delivers a deep, aggressive, and refined sound—even without catalytic converters. Real-world tested on over a dozen vehicles across varied driving conditions, this system reflects over four years of product development and refinement. For enthusiasts running catless setups, this is the most acoustically balanced and performance-driven exhaust solution available for the Audi B8/B8.5 S4 3.0T.

Introducing the CAP Catback Exhaust System – a complete post-catalytic exhaust solution for your Audi B8/B8.5 S4 3.0T. This is not just a rear section like other systems. Ours includes an integrated resonated downpipes, giving you the most exotic, best sounding exhaust on the market. 

Designed to fit after the stock catalytic converters, this full system bolts up cleanly to:

• CAP test pipes
• Other branded test pipes
• CAP longtube headers

Key Benefits Of The CAP Catback System

1. Integrated Midpipe Section: Unlike other systems that start mid-way back, our catback includes a specially designed midpipe/downpipe section for optimized flow and tone from the start.
   
   
2. True 2.5” Mandrel Bent Tubing: Upgraded from the OEM’s restrictive 2.25” pipes, our full 2.5” stainless setup enhances throttle response, horsepower, and torque.
   
   
3. 304 Stainless Steel Throughout: Built to outlast your car—featuring full TIG welding, CNC flanges, and high-grade stainless steel.
   
   
4. Integrated X-Pipe & Resonated Design: Built-in X-pipe smooths out the tone and improves exhaust scavenging. Resonated midpipes help reduce rasp while keeping the aggressive CAP sound.
   
   
5. Quad 90mm or Quad 102mm Gloss Black Exhaust Tips: Dual-wall stainless steel tips for a clean, motorsport-inspired look.
   
   
6. Bolt on Installation: 100% bolt-on fit. Hardware, gaskets, and clamps included.

Real Performance. Real Sound. Real Fitment.

• Gain up to 18 HP when paired with test pipes
• Deep, aggressive tone under load; calm during cruise
  

What’s Included:

• Full catback system with integrated midpipe/downpipe section
• X-pipe and resonated mid-sections
• Rear mufflers with quad polished tips, available in your choice of size:
  • 90 mm diameter
  • 102 mm diameter
• Install kit: stainless steel bolts, gaskets, clamps

Built For Enthusiasts. Engineered By CAP.

CAP’s catback is more than just a rear muffler swap—it’s a full performance solution designed to maximize your 3.0T’s potential in both sound and flow and is the last exhaust system you’ll need.

Although this exhaust will fit both B8/B8.5 Audi S4 equipped with manual transmission & DSG, it is best suited for vehicles with the manual transmission for the best exhaust sound & drone.

*The tunnel brace will need to be spaced out with washers to allow clearance against the exhaust system*