Introduction

Upgrading to an Akrapovic exhaust on your S55-powered BMW (M2 Competition, M3, M4) is one of the most rewarding modifications you can make. The S55 engine already delivers impressive power, but a high-quality exhaust system unlocks a deeper, more aggressive soundtrack and can contribute to modest performance gains through reduced back pressure. This guide provides a comprehensive, step-by-step walkthrough for installing an Akrapovic exhaust system. Whether you choose the Slip-On or Evolution Line, the core process remains similar. Follow each step carefully to ensure a safe, leak-free installation that delivers the sound and performance you expect.

Tools and Materials Needed

Having the right tools on hand before you begin will save time and prevent frustration. Gather the following items:

  • Akrapovic Exhaust System – ensure all components (pipes, muffler, clamps, springs, hardware) are present
  • Socket Set (metric) – 10mm, 13mm, 15mm, 18mm sockets
  • Torque Wrench – range of 10–60 Nm
  • Jack and Jack Stands – four stands recommended for maximum stability
  • Penetrating Oil (e.g., WD-40) – to loosen stubborn bolts
  • Copper Anti-Seize Compound – for exhaust fasteners
  • Safety Glasses and Gloves
  • Heat-Resistant Spray (optional) – for protecting nearby components
  • Pry Bar or Dead-Blow Hammer – may help separate rusted joints
  • Support Stand or Exhaust Hanger Tool – to hold the exhaust during alignment
  • Shop Rags and Degreaser

Preparation Steps

Proper preparation is key to a smooth installation. Take the time to set up your workspace and vehicle safely.

Park and Secure the Vehicle

  • Park the BMW on a flat, level surface. Engage the parking brake.
  • Place wheel chocks behind the rear wheels for added safety.
  • Disconnect the negative battery terminal (use a 10mm socket) to prevent accidental airbag deployment or electrical shorts while working under the car.
  • Allow the exhaust system to cool completely if the vehicle has been driven recently. Hot exhaust components can cause severe burns.

Lift the Vehicle

  • Position a jack under the reinforced rear jack point. Lift the rear of the vehicle high enough to comfortably work underneath.
  • Place jack stands under the designated rear lift points (refer to your owner’s manual). Lower the car onto the stands.
  • Repeat for the front if needed – you’ll want the entire underbody accessible. Four jack stands provide the safest and most stable platform.
  • Once secure, give the car a gentle shake to confirm stability.

Inspect the Stock Exhaust

Before removal, inspect the factory exhaust for any damage or rust. Snap a few reference photos of the routing, hanger positions, and sensor connections. This will help during installation.

Step-by-Step Removal of the Stock Exhaust

Removing the factory exhaust is straightforward, but take care with corroded fasteners. Work methodically to avoid damaging the system or surrounding components.

Loosen the Downpipe Connections

The stock exhaust connects to the turbo downpipes via V-band clamps or bolts (depending on the year). Typically, you’ll find two bolts at each downpipe flange (13mm or 15mm).

  • Spray penetrating oil on the nuts and bolts and let it soak for a few minutes.
  • Use a socket and breaker bar to loosen the bolts. If they resist, apply more oil and give the bolt head a light tap with a hammer.
  • Remove the bolts and set them aside. You may need them for the Akrapovic system, but the kit usually includes new hardware.
  • If your car has oxygen sensors in the downpipe area, carefully unplug them and set them out of the way.

Disconnect the Center Section Hangers

The mid-pipe is supported by rubber hangers. Locate the two hangers near the transmission support crossmember.

  • Use a pry bar or a specialized hanger removal tool to slide the rubber grommet off the metal pin. Work slowly to avoid tearing the rubber.
  • If the rubber is stubborn, apply silicone spray or soapy water to lubricate.
  • Lower the center section slightly and support it with a jack or wooden block.

Remove the Rear Muffler Section

The rear axle-back section has its own set of hangers and must be separated from the mid-pipe.

  • Locate the clamp connecting the mid-pipe to the muffler. Loosen the clamp bolt (usually 13mm) and slide the clamp away.
  • Pull the muffler section apart from the mid-pipe. If it’s stuck, tap the joint with a rubber mallet.
  • Support the muffler as you disengage the rear hangers (two on each side).
  • Carefully lower the muffler to the ground. It is heavy – get a helper if needed.
  • Now the mid-pipe can be lowered and removed. Be mindful of the exhaust valve actuator wiring on some models; disconnect the connector if present.

Remove the Exhaust Valve Actuators (If Equipped)

On many S55 cars, the stock exhaust has electronic valves. They are attached with two small bolts (8mm). Unbolt them and set the actuators aside. The Akrapovic system may reuse these actuators or come with replacement hardware – check the instructions.

Installing the Akrapovic Exhaust

With the stock system out of the way, clean any debris from the mounting points. Now it’s time to install the Akrapovic system. Follow the order in your specific kit’s manual, but the general process is as follows.

Install the Mid-Pipe Section

  • Position the Akrapovic mid-pipe under the car, aligning it with the downpipe outlets. If the system includes a single mid-pipe (most do), route it above the rear subframe brace.
  • Apply a thin layer of copper anti-seize to the downpipe-to-midpipe flange bolts. This prevents seizing and aids future removal.
  • Install the supplied bolts and tighten them hand-tight. Do not fully torque yet.
  • Attach the rubber hangers to the mid-pipe pins. Use a little lubricant if needed.

Install the Rear Muffler Section

  • Slide the rear muffler section into position. Connect it to the mid-pipe using the provided slip-joint or clamp. Again, hand-tighten only.
  • Engage the rear hangers on both sides. You may need to push the muffler upwards while a helper slides the hanger grommets over the pins.
  • If your Akrapovic system includes valve actuators, mount them using the supplied bracket. The connectors should click in securely. Route the wiring harness away from hot exhaust surfaces.
  • Install the tailpipe tips loosely at this stage. You will align them later.

Connect the Exhaust Tips

Akrapovic provides beautiful titanium or carbon-fiber tips. Place them over the tailpipe outlets and adjust for a perfect fit – centered in the bumper cutouts and parallel to the ground. Tighten the set screws or clamp bolts gently.

Tighten All Fasteners to Spec

Now that the entire system is loosely hung, tighten everything in a logical sequence:

  1. Start at the downpipe connections. Torque the bolts to 30 Nm (22 lb-ft) using a torque wrench. Work in a cross pattern for even clamping.
  2. Move to the mid-pipe-to-muffler clamp. Torque to 15 Nm (11 lb-ft) – do not overtighten, as the slip joint needs to allow a tiny bit of movement for thermal expansion.
  3. Tighten all hanger bolts and bracket fasteners to the values in your Akrapovic manual (typically 8–10 Nm).
  4. Finally, tighten the tip set screws to the manufacturer’s recommendation (often 5 Nm).

Final Adjustments and Checks

After tightening, inspect every joint and hanger one more time. Check for clearance around the rear subframe, sway bar, and chassis rails. The S55 engine produces a lot of heat and vibration – you want no metal-to-metal contact.

  • Rotate the tailpipe tips by hand to ensure they don’t contact the bumper. Adjust as necessary.
  • Check that the exhaust valves (if equipped) open and close freely. Manually cycle them with a 12V power source if needed.
  • Apply heat-resistant spray to nearby wiring, plastic components, or rubber bushings that are within 6 inches of the exhaust. This is optional but highly recommended for longevity.

Reconnecting and Testing

With the exhaust fully installed and adjusted, perform final checks before starting the engine.

  • Reconnect the negative battery terminal. Tighten the clamp securely.
  • Double-check that all tools, rags, and loose objects are removed from the engine bay and undercarriage.
  • Start the engine and let it idle. Listen for any exhaust leaks – a ticking or hissing sound indicates a loose connection. If you hear a leak, shut off the engine and re-check the affected joint.
  • While the engine idles, inspect the exhaust path for smoke or signs of contact with chassis components.
  • Allow the engine to reach operating temperature. You may notice a faint burning smell for the first few minutes as oils and residues on the new exhaust burn off – this is normal.
  • Take the car for a test drive. Go through a variety of RPM ranges and light to moderate throttle. The Akrapovic exhaust will be louder than stock, especially under load. Note any drone or unwanted vibrations.
  • Return to your workspace and park. Re-check the torque on all visible fasteners after the first heat cycle – thermal expansion can sometimes cause nuts to loosen slightly.

Maintenance Tips for Your Akrapovic Exhaust

Akrapovic systems are built to last, but a little care goes a long way. Here are a few tips:

  • Clean the titanium tailpipe tips with a mild detergent and a soft cloth. Avoid abrasive cleaners that could scratch the finish.
  • Periodically inspect the rubber hangers for cracking, especially in cold climates.
  • Retighten the exhaust clamp bolts after the first 500 miles, as gaskets and joints settle.
  • If you notice a change in sound quality, check for leaks at the downpipe connections – this is the most common area for bolts to back out.

Conclusion

Installing the Akrapovic exhaust on your S55-powered BMW transforms the driving experience. The deeper, richer tone at idle and the ferocious scream at full throttle are unmatched by most aftermarket systems. Beyond the sound, you’ll enjoy a slight weight reduction and a more responsive throttle feel. By following this guide and taking your time with each step – especially the torque specs and alignment – you’ll achieve a professional-grade installation that lasts for years. For more information on Akrapovic’s product line for the S55, visit the official Akrapovic website. For torque specs and additional S55 technical details, consult the BMW TIS (Technical Information System). And for community insights and build threads, the Bimmerpost F80 forum is an excellent resource.