Why Upgrade Your Challenger’s Exhaust?

Your Dodge Challenger’s factory exhaust system is engineered for a compromise: acceptable sound, moderate flow, and cost efficiency. Aftermarket systems from Borla and Flowmaster unlock additional horsepower, reduce back pressure, and deliver a signature note that turns heads. Whether you daily drive your Challenger, hit the strip, or just want a more aggressive presence, a cat-back or axle-back system is one of the most rewarding upgrades you can make.

This guide covers everything from selecting the right system to performing a clean, professional-grade installation. We’ll dive deep into the characteristics of each brand, the tools you’ll need, step-by-step removal and installation procedures, torque specs, and post-installation checks. By the end you’ll have the confidence to tackle the job in your own garage.

Borla vs. Flowmaster: Which Sound Matches Your Style?

Both Borla and Flowmaster are American icons with decades of exhaust engineering experience. However, their design philosophies and sound signatures diverge significantly.

Borla Exhaust Systems

Borla exhausts are crafted from T-304 stainless steel (marine-grade) and feature straight-through, multi-core muffler technology. The result is a crisp, aggressive, and metallic tone without drone. Borla offers three main sound levels:

  • Borla Touring: Mild but still more aggressive than stock. Ideal for daily drivers who want a deeper tone without cabin resonance.
  • Borla S-Type: The most popular choice. Balanced aggressive sound at wide-open throttle yet civil during cruising. Features Helmholtz tuning chambers to eliminate drone.
  • Borla ATAK: “Attack” mode. Extremely aggressive, track-ready sound. Expect loud, raw WOT bark with some low-rpm rumble.

All Borla systems are backed by a Million-Mile Warranty. They are mandrel-bent and use aircraft-grade hangers. Borla systems typically increase horsepower by 8–12 hp on the Challenger 5.7L and 6.4L models.

Flowmaster Exhaust Systems

Flowmaster is synonymous with American muscle car sound: deep, guttural, and classic. They use chambered muffler technology that reflects sound waves to create its signature rumble. Flowmaster offers numerous muffler series and complete cat-back kits:

  • Flowmaster American Thunder: Classic 40 Series muffler sound. Loud under throttle but surprisingly quiet at cruise. Drone can be present on some setups.
  • Flowmaster Outlaw: Aggressive and raw. Uses a Super 10 muffler for the loudest Flowmaster sound. No drone because the muffler is essentially straight-through with minimal baffling – but very loud.
  • Flowmaster Force II & Pro Series: More refined, designed to reduce drone while still offering performance gains. Good for daily drivers who want a moderate upgrade.

Flowmaster systems are built from aluminized steel (standard) with an optional upgrade to stainless. They are generally more affordable than Borla but may have a shorter lifespan in salt-belt climates. Expected horsepower gains: 6–10 hp.

Sound Comparison: Real-World Considerations

Listen to sound clips on YouTube for both brands before purchasing. Borla’s ATAK is sharper, while Flowmaster’s American Thunder is deeper and rumbles at idle. Borla tends to be louder at high RPM, Flowmaster is louder at low RPM. Neither is “better” – it’s purely preference. We recommend Borla for those who want a modern, refined aggressiveness and Flowmaster for traditional muscle car fans.

Before installing, know your local laws. In many states, a cat-back or axle-back exhaust is legal because it does not remove catalytic converters. However, some systems may exceed noise limits. Borla and Flowmaster both offer systems that are 50-state legal (CARB EO number may apply for certain mufflers). Check the product page for legal disclaimers. If you live in a state with strict emissions testing, ensure you retain all factory catalytic converters.

Tools and Materials – What You’ll Actually Need

Beyond the basics, having the right tools will prevent frustration. Here’s a comprehensive list:

  • Floor jack and two heavy-duty jack stands (3-ton capacity minimum)
  • Wheel chocks
  • Metric socket set (10mm, 13mm, 15mm, 18mm – the latter for exhaust manifold bolts)
  • Socket wrench, ½” drive for larger bolts
  • Combination wrenches: 10mm, 13mm, 15mm
  • Penetrating oil (e.g., PB Blaster or WD-40 Specialist)
  • Exhaust hanger removal tool (or large flathead screwdriver + pliers)
  • Wire brush for cleaning flanges
  • Torque wrench (ft-lb)
  • Safety glasses and mechanic’s gloves
  • Ramps (optional, but helpful)
  • New exhaust gaskets if not included with your kit – often 2.5” or 3” donut gaskets
  • Anti-seize compound (for bolts)
  • Exhaust sealant for slip-joints (optional, most modern systems use mechanical clamps)

Pro tip: If your car has rusted bolts, spray penetrating oil on every fastener the night before. It makes removal far easier.

Preparation: Setting Up Your Work Area

Safety cannot be overstated. Park on level concrete. Engage the parking brake. Place wheel chocks behind the front tires (or rear, depending on drive). Disconnect the negative battery terminal – this prevents accidental short circuits and resets the ECU for the new adaptive learning.

Loosen the fuel filler cap momentarily to relieve pressure, then retighten (not strictly necessary but a good habit). Let the exhaust cool completely if the car was run recently. Working on a hot exhaust is dangerous and can cause burns.

Step 1: Removal of the Factory Exhaust System

This process applies to both cat-back and axle-back replacements. The factory system is one piece from the catalytic converters to the rear mufflers/tips. On Challengers (2008+), the exhaust is supported by rubber hangers at several points.

Procedure:

  1. Raise the rear of the vehicle high enough to clear the exhaust tips. Position jack stands under the rear subframe or dedicated lift points. Never rely on the jack alone.
  2. Spray the exhaust flange bolts at the catalytic converter outlets (two flanges, each with two bolts) and every hanger rubber with penetrating oil. Wait 5 minutes.
  3. Remove the two bolts at each converter flange using a 15mm socket. The nuts may be seized; use a breaker bar if needed. If they spin, use a wrench to hold the backside nut. Some Hemi engines use spring bolts – remove the nuts and slide the springs off.
  4. Carefully disconnect the mid-pipe from the converters. It may require slight twisting or leverage. Do not hit the catalytic converter.
  5. Using an exhaust hanger tool or a flathead screwdriver, pry the rubber hangers off the metal studs on the exhaust. There are typically three: one near each rear muffler and one near the axle bend. Work from the back forward.
  6. Lower the old exhaust system. It may be heavy; have a helper support it. Slide it out from under the car.
  7. Clean the flanges on the catalytic converters with a wire brush. Remove any gasket residue.

Note: On V6 models (3.6L), the exhaust routing is similar but uses smaller diameter piping. The same steps apply.

Step 2: Test-Fit the New System (Borla or Flowmaster)

Before final assembly, loosely hang all sections to check alignment. Most Borla and Flowmaster kits include clamps and hangers. For Borla, the system is typically shipped in two or three sections: mid-pipe (or over-axle pipe), mufflers, and tips. Flowmaster may have separate mufflers and tailpipes.

Key checks:

  • Ensure the mid-pipe aligns with the converter flanges. Some fitment requires rotation of the flanges to clear the transmission crossmember.
  • Check that the mufflers do not contact the rear axle, fuel tank heat shield, or spare tire well. A gap of at least 1 inch is recommended.
  • Tips should be centered in the rear fascia openings. Adjust the hanger positions or slide the tips in/out to achieve perfect alignment.

For Borla kits, the hangers are welded to the pipes and are exact-fit. For Flowmaster, you may need to attach separate hangers with clamps. Follow the included instructions.

Step 3: Install the New Exhaust

Once test-fit is satisfactory, begin permanent installation.

  1. Apply anti-seize to the threads of all bolts (except spring bolts – leave those dry). Also apply a small smear to the slip-joints if your system uses band clamps.
  2. Install gaskets on the converter flanges (the kit should include new gaskets; if not, use OEM-style metal-reinforced gaskets).
  3. Attach the mid-pipe to the converters with the original nuts/bolts. Torque to 30–35 ft-lb (40–47 Nm). Do not overtighten the spring bolts; the springs should compress about halfway.
  4. Install the over-axle pipe (if separate) and mufflers. Use the provided clamps. Hand-tighten only at this stage.
  5. Reconnect rubber hangers. If the new hangers are rubber, reattach them to the body studs. For Borla, the hangers are often metal with rubber inserts – push the rubber over the studs or use pliers.
  6. Attach the rear tips. Adjust them so they are centered and the tip angle matches the bumper cutout.
  7. Once everything is aligned, tighten all clamps and bolts. Exhaust clamps should be torqued to 30–40 ft-lb (40–54 Nm). Do not exceed the manufacturer’s spec. Ball-flange connections (on some Borlas) require 15 ft-lb.
  8. Double-check all hangers are properly seated and that the exhaust does not rattle against the underbody.

Pro tip: Use a ratcheting strap to hold the exhaust in place while adjusting – it gives both hands free.

Step 4: Final Checks and Test Drive

Before lowering the car, perform a full visual inspection. Start the engine with the car still on jack stands (in Park/Neutral with parking brake). Listen for leaks at all joints. A small exhaust leak will sound like a tick or hiss. If you hear one, tighten the clamp or re-seat the gasket.

Lower the car and reconnect the battery. Start the engine again and let it idle for 2 minutes to let the ECU adapt. Listen for rattles inside the cabin. If you experience drone at cruising RPM (typically 1500–2000), it may be the price of a louder system. Borla’s S-Type and Touring minimize drone effectively; Flowmaster’s 40 series may drone on some Challenger models.

Take a short test drive (5–10 miles). Vary engine speeds and loads. After returning, check all joints for leaks with your hand (use caution – exhaust gets hot!). Re-torque clamps if needed after a heat cycle. Many systems require retightening after the first 100 miles.

Performance Expectations and Break-In

You will notice a more responsive throttle and a slight increase in horsepower and torque, especially in the mid-range. Claimed gains are 8–12 hp for Borla, 6–10 hp for Flowmaster on 5.7L and 6.4L engines. Real-world gains depend on the rest of your intake/exhaust mods. The sound will deepen slightly over the first 500 miles as soot coats the muffler packing (in Borla’s case) or as the chambered mufflers break in.

Some ECU recalibration occurs naturally; the engine may feel slightly different after 50 miles. If you installed a cat-back, no tune is required. For long-tube headers or full exhaust, a custom tune is recommended.

Common Pitfalls and How to Avoid Them

  • Forgetting gaskets: Always use new gaskets at the converter flange. Reusing old ones can cause leaks.
  • Overtightening clamps: Band clamps deform if overtorqued. Stick to the spec.
  • Incorrect tip alignment: Adjust before final tightening. Once clamped, the pipe may rotate slightly – check again.
  • Not using anti-seize: Stainless steel bolts can gall. Anti-seize prevents seizing.
  • Hanger contact: If a hanger rubs the frame, add a rubber isolator or slightly bend the hanger (gentle heat + pliers).

External Resources

For detailed product information, including sound clips and fitment guides, visit the official websites:

Conclusion

Upgrading your Dodge Challenger’s exhaust to a Borla or Flowmaster system is one of the most satisfying modifications you can perform in your home garage. You gain authentic American muscle sound, modest performance gains, and a more engaging driving experience. This guide has walked you through selection, preparation, removal, installation, and final tuning. Approach the job methodically, respect torque specs, and you’ll enjoy years of trouble-free operation. Whether you choose Borla’s engineering precision or Flowmaster’s classic rumble, your Challenger will thank you with every start-up.