Introduction

The Audi B8 S4, equipped with its supercharged 3.0-liter V6, is already a formidable performance sedan. However, the factory exhaust system is designed primarily for noise compliance and cost-effectiveness, often leaving enthusiasts wanting a more aggressive soundtrack and noticeable performance gains. Upgrading to a high-quality aftermarket system like the Akrapovic exhaust can transform the driving experience. Akrapovic, a Slovenian manufacturer renowned for its motorsport heritage and use of premium materials like titanium and carbon fiber, offers a system specifically engineered for the B8 S4. This guide provides a comprehensive, step-by-step walkthrough for removing the stock exhaust and installing an Akrapovic system in your garage. By following these instructions carefully, you can achieve a professional-grade installation that unlocks the full potential of your S4’s exhaust note and performance.

Tools and Materials Needed

Gathering the correct tools before you begin will save time and frustration. The following list includes both standard automotive tools and specialized items required for this specific installation.

  • Socket wrench set with metric sockets (10mm, 13mm, 15mm, 18mm are most common)
  • Torque wrench (capable of 15–50 ft-lb range)
  • Flathead and Phillips screwdrivers
  • Jack and jack stands (two stands minimum; four for leveling)
  • Exhaust hanger removal tool (or large flathead screwdriver and WD-40)
  • Penetrating oil (e.g., PB Blaster or Liquid Wrench)
  • Akrapovic exhaust system (including all clamps, brackets, and hardware provided in the kit)
  • Mechanics gloves and safety glasses
  • Rags or shop towels
  • Optional: ramp or lift for more comfortable access

Ensure your Akrapovic kit is complete per the included inventory sheet. Common omissions are often the gaskets if not pre-installed on the downpipe connections; verify you have the correct ring or flat gaskets.

Preparation Steps

1. Safety and Workspace Setup

Work in a well-ventilated area, preferably a garage with the door open or a driveway. The exhaust system will be hot if the car was driven recently; allow the vehicle to cool completely. Wear gloves to protect against sharp edges and hot components, and safety glasses to shield from debris or dripping fluids.

2. Raise and Secure the Vehicle

Park on a level surface, engage the parking brake, and chock the front wheels. Position the jack under the rear differential or a reinforced chassis point (consult your owner’s manual) and lift the rear of the vehicle. Place jack stands under the designated lift points on the rear subframe or side sills. Double-check that the car is stable before crawling underneath. Raising the car approximately 18-24 inches provides comfortable working clearance.

3. Remove the Stock Exhaust

The factory exhaust from the B8 S4 is a two-piece system: the downpipes (connected to the cat or turbo outlet) and the mid/rear section. The Akrapovic system typically replaces everything from the downpipe flanges backward.

A. Disconnect the Downpipe-to-Cat Connection
Locate the two bolts (one on each downpipe) securing the exhaust to the rear of the catalytic converters or the downpipes themselves. These bolts are often 13mm and can be heavily corroded. Apply penetrating oil and allow it to soak for 10 minutes. Use a socket and breaker bar to loosen them. If they are stubborn, use a ratchet with a pipe extension. Keep these bolts; they will be reused for the Akrapovic system unless the kit provides new ones.

B. Remove the Exhaust Hangers
The stock exhaust is held up by four rubber hangers (two on the mid section, two near the mufflers). Use an exhaust hanger removal tool or a large flathead screwdriver to pry the hanger away from the metal stud on the chassis. Applying a bit of soapy water or WD-40 around the rubber bushing eases removal. Work the hangers off one by one.

C. Lower and Remove the Factory Exhaust
With the downpipe bolts loosened and hangers detached, the system will be supported only by the remaining hanger near the mufflers. Have a helper steady the system, then slide the exhaust forward slightly to clear the downpipe flanges. Lower it carefully and slide it out from under the car. The B8 S4 stock exhaust is heavy (approximately 50-60 lbs), so use proper lifting technique. Place the stock system aside.

Note on Catalyst / Secondary Cat Considerations: Some Akrapovic systems for the B8 S4 replace the secondary catalytic converters. If your configuration includes this, you may need to unbolt the secondary cats from the primary downpipes. Check your specific Akrapovic part number instructions.

Installing the Akrapovic Exhaust System

With the stock exhaust removed, inspect the downpipe flanges for damage or rust. Clean the mating surfaces with a rag and ensure the gasket surfaces are smooth. The Akrapovic system comes pre-assembled from the factory, but you may need to adjust fitment of individual sections.

1. Position the New Exhaust

Carefully lift the Akrapovic exhaust (note it is lighter than stock, often titanium) and place it on the ground under the vehicle. Align the front connections with the downpipe flanges. The system is designed to be installed in sections, but most aftermarket exhausts are continuous. Do not fully tighten anything yet. Slide the system forward so the front flanges mate with the downpipe outlets.

2. Attach the Exhaust to the Downpipes

Install the bolts (reuse factory bolts or use provided Akrapovic hardware) through the flanges and hand-tighten them. If your kit includes a two-bolt flange, ensure the bolts are oriented correctly and the gasket is seated. For V-band clamps, ensure the clamp is correctly positioned over the flange lips before tightening. Torque the bolts to the specifications provided by Akrapovic (typically 15-20 ft-lb for M8 bolts) or the factory spec (24 ft-lb for the downpipe-to-cat connection). A torque wrench is critical to avoid stripping threads or warping flanges.

3. Secure the Exhaust Hangers

Working from front to rear, attach the rubber hangers to the metal pegs on the chassis. The Akrapovic system typically comes with new rubber hangers or is designed to fit the factory hangers. Use the hanger removal tool or soapy water to slide them onto the studs. Ensure each hanger is fully seated and that the exhaust is not contacting any underbody braces or heat shields. The tips should be roughly centered in the bumper cutouts. Adjust the hanger positions by sliding the rubber pieces if needed.

4. Align Exhaust Tips

The final alignment step is crucial for appearance. Loosen the tip clamps (usually included with the Akrapovic system) and slide the tips outward or inward until they are symmetrically positioned in the bumper valance. The B8 S4 rear diffuser has specific cutouts; aim for 5-10mm of gap on all sides. Tighten the tip clamps to 12-15 ft-lb. Verify the tips are parallel to the ground and not touching the bumper.

5. Check Clearance and Connections

After tightening all major connections, inspect the entire exhaust route. Look for contact with the driveshaft (especially on the driver side), sway bar, or heat shields. If the Akrapovic system seems too close to any component, loosen the hanger and shift the system slightly. The titanium material expands when hot, so leave at least 5mm of clearance. Double-check the tightness of all bolts and clamps.

Post-Installation Checks

1. Inspect for Leaks

Before lowering the car, start the engine briefly (while it is still on jack stands) and listen for any hissing or ticking sounds that indicate an exhaust leak. Place a rag near the tailpipes and feel for air leaks around each joint. A small amount of soapy water applied to the joints can help identify leaks via bubbles. If a leak is detected, tighten the clamp or bolt further. Most Akrapovic systems use a multi-layer metallic gasket that requires a proper crush to seal.

2. Lower the Vehicle

Turn off the engine and allow it to cool. Remove jack stands and lower the vehicle carefully. Once on the ground, re-check tip alignment and clearance as the suspension settles.

3. Recheck Torque After Heat Cycling

After the first 50-100 miles of driving, the exhaust system will have undergone thermal expansion and contraction. It is recommended to retorque all bolts and clamps to the specified values. This prevents rattles and ensures long-term sealing.

4. Sound and Performance Break-In

The Akrapovic exhaust will sound deeper and more aggressive immediately, especially at cold start. However, the sound will evolve over the first 500 miles as the packing material and titanium structure settle. Expect a slight metallic undertone that mellows into a refined but aggressive note. Performance gains are modest (typically 5-10 horsepower and torque improvements from reduced backpressure), but the throttle response becomes sharper due to decreased exhaust restriction.

Additional Considerations for B8 S4 Owners

Valved Options

Some Akrapovic exhausts for the B8 S4 include electronic valves that integrate with the factory Audi Drive Select system. If your system is valved, you will need to connect the actuator wiring. Typically, this involves splicing into the factory wiring or using plug-and-play adapters. Ensure the valve is functioning properly before final assembly.

Drone and Resonance

The B8 S4 is prone to interior drone at certain RPMs, especially with aftermarket exhausts. Akrapovic systems are engineered to minimize drone through Helmholtz resonators or specific layout. If you experience excessive drone, check that all hangers are installed and that the exhaust is not vibrating against the underbody. Adding exhaust hangers or upgrading the transmission mount can help.

Warranty Considerations

Installing an aftermarket exhaust does not void the entire car warranty, but any issues directly caused by the aftermarket part (e.g., a due to a leak affecting oxygen sensors) may not be covered. Keep the original exhaust in case you need to revert for dealer visits.

Conclusion

Installing an Akrapovic exhaust system on your Audi B8 S4 is a rewarding project that delivers a noticeable upgrade in sound, weight reduction, and driving pleasure. By following the detailed steps outlined above—from safe vehicle lifting to proper torque procedures and alignment—you can complete the installation in a weekend with basic mechanical skills. The result is a more engaging driving experience, whether cruising or pushing the car on back roads. Take your time, work methodically, and enjoy the process of improving your S4.