The AWE Tuning Cat-back Exhaust system for the Audi B8 S4 (2010–2016) has earned a reputation as one of the most refined aftermarket exhaust options for the 3.0T supercharged V6. Enthusiasts choose it not just for the aggressive soundtrack, but for measurable performance improvements, lighter weight, and Audi-like fit and finish. This guide covers everything you need to know—from the engineering behind the system to the step-by-step installation, real-world dyno gains, and total cost of ownership. Whether you are a weekend DIYer or planning to hand the job to a shop, the information here will help you make an informed decision and execute the upgrade correctly.

Understanding the AWE Tuning Cat-Back Exhaust System

AWE Tuning is a Pennsylvania-based company with a strong following in the European performance car community. Their cat-back exhaust for the B8 S4 replaces the entire exhaust from the catalytic converters rearward. It consists of mandrel-bent 2.5-inch 304 stainless steel tubing, a choice of resonated or non-resonated center sections, and precision-welded tips in either polished stainless or the signature Diamond Black heat-resistant coating.

The key design goal is to reduce back pressure while maintaining a clean, drone-free sound. The factory exhaust on the B8 S4 is heavily muffled and uses several restrictive crush-bent sections. By smoothing the flow path and using free-flowing straight-through mufflers, the AWE system unlocks additional horsepower and torque. The resonated version adds a Helmholtz-style resonator that cancels out the 1,800–2,200 rpm drone frequency common in many aftermarket exhausts—making it a favorite for daily drivers who still want an aggressive note under throttle.

The system is available in two tip configurations: the 102mm double-walled tips (for a bold, contemporary look) and the 90mm single-walled tips (a more OEM+ appearance). Both are available in chrome or Diamond Black. The resonated setup is slightly heavier due to the larger resonator but still shaves about 20–25 pounds off the stock exhaust, which weighs approximately 55–60 pounds. The non-resonated version sheds even more weight and produces a louder, raspier tone that some track-oriented owners prefer.

Performance Gains: What the Numbers Show

Claims of 15–20 horsepower gains are common, but independent dyno testing on the 3.0T engine typically shows more modest but still meaningful improvements. With the AWE cat-back alone, most owners report a peak gain of 10–14 horsepower and 12–16 lb-ft of torque at the wheels. The gains are most noticeable in the mid-range (3,500–5,500 rpm), where the engine pulls harder and the throttle response feels sharper. The weight reduction of roughly 25 pounds also improves acceleration and handling, especially when combined with other bolt-ons like an intake or a tune.

It is important to note that these gains are on a stock engine. If you have already installed a Stage 1 or Stage 2 tune, the exhaust becomes even more effective because the increased airflow matches the higher boost levels. Some tuned cars see gains of 18–22 wheel horsepower when adding the AWE cat-back. The system also pairs well with aftermarket downpipes, though that is a separate upgrade requiring more labor and cost.

Beyond peak numbers, the improved exhaust flow reduces turbo spool-up lag slightly (the 3.0T uses a supercharger, so lag is minimal, but the exhaust note makes the power delivery feel more immediate). You will also notice a cleaner, more linear power curve in the upper rev range where the stock exhaust chokes the engine.

Real-World Driving Impressions

On the road, the performance difference is tangible. The car feels freer to rev, especially in the 4,000–6,500 rpm range. Merging onto highways and overtaking require less pedal input. The sound is more aggressive but never offensive in the resonated version; the non-resonated is louder and more raw, which some find thrilling and others tire of on long trips. Both versions eliminate the slightly muted, aspirated sound of the stock exhaust and replace it with a crisp, European V6 growl.

Sound Profile: Tailoring the Note to Your Taste

The acoustic character of the AWE system varies significantly between the resonated and non-resonated options. The resonated version is the top seller for good reason: it delivers a deep, refined rumble at idle, a muscular bellow under hard acceleration, and near-silent cruising at highway speeds (no drone). Cold starts are noticeably louder but settle quickly. The non-resonated system is louder at all rpm, with more crackle on deceleration and a sharper, more aggressive tone. It can drone slightly between 1,800–2,200 rpm, though many owners find it acceptable for weekend driving.

AWE Tuning provides sound clips on their website and there are countless video reviews on YouTube. (Search for “AWE B8 S4 resonated vs non-resonated” to hear the difference before buying.) The material finish also affects appearance: the Diamond Black coating resists heat discoloration and looks stealthy, while polished stainless gives a bright, refined look.

Installation: A Detailed Walkthrough

Installing the AWE cat-back is a solid weekend project for someone with basic mechanical skills. Expect to spend 3–5 hours if you work slowly and carefully. Access to a lift makes the job easier, but jack stands are perfectly adequate. Below is an expanded step-by-step guide, including common pitfalls.

Tools and Supplies Needed

  • 3/8" and 1/2" drive socket set with metric sockets (10mm, 13mm, 15mm, 18mm, 22mm)
  • Ratchet and extensions (6" and 12")
  • Breaker bar for stubborn bolts
  • Torque wrench (capable of 30–80 ft-lbs)
  • Cut-off wheel or reciprocating saw (for cutting stock exhaust if needed)
  • Penetrating oil (e.g., PB Blaster or WD-40 Specialist)
  • Jack and two jack stands (minimum 3-ton capacity)
  • Safety glasses and gloves
  • Pry bar or exhaust hanger removal tool
  • New exhaust gaskets (optional, but recommended if yours are aged)

Preparation

Park the car on level ground. Disconnect the negative battery terminal (optional but good practice when working near electronics). Lift the rear of the car high enough to work comfortably under it, and place jack stands under the designated lift points on the pinch welds. Never rely on the jack alone.

Removing the Stock Exhaust

Start by spraying penetrating oil on all exhaust hangers, clamps, and bolts—especially the bolts connecting the cat-back to the downpipes (these are often rusted). Let it soak for 10–15 minutes. The stock exhaust is held by three rubber hangers and one clamp near the catalytic converters. Use a 13mm socket to loosen the clamp. You may need to cut the stock exhaust if it's one-piece; the factory system is welded from the downpipe flange to the rear mufflers. Many people cut the stock pipe just behind the rear axle with a sawzall to make removal easier. Alternatively, you can unbolt the entire system from the downpipe flange, but that requires dropping the rear subframe slightly—more work than necessary.

Once cut or unbolted, wiggle the exhaust free from the rubber hangers. Spraying soapy water on the hangers helps them slide off. Carefully lower the exhaust—enlist a helper as it is heavy and awkward.

Installing the AWE System

The AWE system comes in several pieces: the front pipe (with or without the resonator), the mid-pipe, the rear muffler section, and the tips. Lay out all parts and verify they match your order (resonated vs non, tip style). Do not tighten anything fully until the entire system is aligned.

  • Attach the front pipe: Slide the front pipe into the downpipe flange using the provided gasket and bolts. Hand-tighten the bolts.
  • Connect the mid-pipe: Slide the mid-pipe onto the front pipe using the supplied band clamp. Leave the clamp loose.
  • Install the rear muffler section: Attach the rear section to the mid-pipe with another band clamp. Then slide the rubber hangers onto the existing mounting points on the car. For the rear hangers, you may need to use a pry bar to stretch the rubber over the metal studs.
  • Attach the tips: Slip the tips over the rear outlets and adjust them so they are even and centered in the bumper cutouts. Tighten the set screws firmly.

Final Alignment and Torquing

With all components loosely assembled, step back and check the tip position. The tips should be evenly spaced from each other and from the bumper. Adjust the band clamps and the front pipe connections as needed. Once satisfied, torque all bolts and clamps to the following specs (from AWE Tuning instructions): front flange bolts to 30 ft-lbs, band clamps to 45 ft-lbs. Re-check after 100 miles and re-tighten if necessary, as the clamps can bed in slightly.

Testing and Common Issues

Start the engine and listen for leaks. A small puff of smoke or a hissing sound indicates a leak. Often it is a loose clamp or a misaligned gasket. If you get drone in the resonated version, check that the resonator is not contacting the chassis—sometimes a hanger is mispositioned. The non-resonated system may drone slightly; this is normal, but ensure the pipe is not touching the underbody. Let the engine idle and then rev it to 3,000 rpm to cycle the exhaust through its range. Take a short test drive, then re-check all clamps under the car after the system has heated and cooled.

Costs: Breaking Down the Investment

The AWE cat-back is a premium upgrade, and the total cost depends on configuration and installation method. Below is a realistic estimate as of 2025.

ComponentPrice Range
AWE Cat-Back Exhaust (resonated, 102mm tips)$1,595–$1,799
AWE Cat-Back Exhaust (non-resonated, 90mm tips)$1,495–$1,695
Diamond Black tip upgrade (add)$150–$200
Professional installation (indie shop)$200–$400
Professional installation (dealer or Euro specialist)$400–$600
Optional gaskets, hardware, hangers$30–$80

If you do the install yourself, you save the labor fee but should budget for incidental supplies like penetrating oil and possibly a sawzall blade. The total DIY cost is roughly $1,600–$1,900; with professional install, $1,900–$2,400. This puts the AWE system in the upper-mid range of aftermarket cat-backs for the B8 S4, but the quality and drone-free engineering justify the price. Compare this to systems from Milltek (similar pricing) or MagnaFlow (slightly cheaper but often louder and less refined).

There is also a strong resale market. A used AWE system in good condition typically sells for $700–$1,000 on forums and eBay, so you recoup a significant portion if you ever sell the car.

Long-Term Ownership: Maintenance and Durability

The 304 stainless steel construction resists corrosion far better than the factory aluminized steel. That said, if you live in the salt belt, the clamps and hardware can still rust. Apply anti-seize to the band clamp threads and the flange bolts during installation. Clean the tips regularly with stainless steel polish to prevent water spots and road grime buildup. The Diamond Black coating is more durable than painted coatings but can chip if struck by rocks; avoid using abrasive wheel cleaners on them.

The rubber hangers may sag over time (especially if you drive hard on rough roads). Replacement hangers are available from AWE or aftermarket suppliers for around $20 each. The band clamps use a locking mechanism that can loosen after many heat cycles; inspect them every oil change and re-torque if needed. The mufflers and resonators are fully welded and should never need internal service.

If you later decide to add downpipes, the AWE cat-back remains compatible, though the sound will become significantly louder—most owners pair it with resonated downpipes to keep noise in check.

Conclusion

The AWE Tuning Cat-back Exhaust for the B8 S4 delivers exactly what enthusiasts want: genuine power gains, a weight reduction, a customizable sound profile, and fitment that mimics OEM quality. The installation is manageable for a home mechanic with patience, and the long-term durability is excellent. While the initial cost is higher than some competitors, the drone-free resonated version and the availability of multiple tip finishes make it a versatile choice that stands the test of time. Whether you are building a weekend warrior or a refined daily driver, this exhaust will elevate the driving experience without introducing the annoying resonances that plague lesser systems. For those ready to pull the trigger, check out the product page at AWE's official site, browse owner reviews on Audizine, and find the best price from a trusted retailer like FCP Euro or ECS Tuning.