Installing a Borla exhaust system on your Mazda Miata is one of the most rewarding upgrades you can make. Borla has a well-earned reputation for crafting stainless steel exhausts that deliver a deep, aggressive tone without excessive drone, and their Miata systems are no exception. Whether you drive an NA, NB, NC, or ND generation, a Borla exhaust not only improves the sound character but also reduces back pressure, freeing up a few horsepower and pounds of torque. However, achieving that perfect fit requires a methodical approach and attention to detail. This comprehensive guide walks you through every step—from gathering the right tools to performing the final torque check—so your Borla exhaust installs cleanly, seals tightly, and transforms your Miata’s driving experience.

Tools and Materials Needed

Having the correct tools on hand before you lift the car will save time and frustration. The Borla exhaust system typically includes the muffler, mid-pipe, and hardware, but you may need additional items depending on your Miata’s age and condition. Gather the following:

  • Jack and jack stands – A floor jack and a pair of sturdy stands are essential for safe access.
  • Socket wrench set – Metric sockets, particularly 10mm, 12mm, 14mm, and 17mm, cover most Miata exhaust fasteners.
  • Torque wrench – Needed to tighten bolts to factory specifications without over-tightening.
  • Rubber mallet – For persuading stubborn hangers without damaging the rubber.
  • Penetrating oil – Spray like PB Blaster or WD-40 Specialist helps loosen rusted bolts and hanger studs.
  • New exhaust gaskets – The stock gasket at the catalytic converter connection should be replaced. Borla may include one; if not, buy an OEM-quality replacement.
  • Anti-seize compound – Apply to bolt threads during reassembly to prevent future corrosion.
  • Safety glasses and gloves – Protect yourself from debris, rust, and sharp edges.
  • Exhaust hangers (if needed) – Inspect the stock hangers; replace any that are cracked or stretched.

Preparation Steps

Begin by parking your Miata on a level, solid surface. Allow the engine and exhaust components to cool completely—touching a hot catalytic converter or muffler can cause burns. Put on your safety glasses and gloves. Then raise the rear of the vehicle using a floor jack, positioning jack stands under the designated lift points (typically the frame rails or differential for the rear). Never rely solely on a jack. Once secure, give the car a gentle shake to confirm stability.

Take a moment to spray penetrating oil onto all exhaust bolts and rubber hanger studs. Allow it to soak for at least ten minutes while you gather your tools. This step significantly reduces the chance of snapping a bolt, especially on older Miata models with rust-prone hardware.

Removing the Stock Exhaust

Removing the factory exhaust is straightforward, but patience pays off. The procedure is nearly identical across all Miata generations, though exact bolt sizes may vary slightly.

  1. Loosen the bolts at the catalytic converter. Use a socket wrench to break free the two (or three, on some models) bolts connecting the mid-pipe flange to the cat. If they feel tight, apply more penetrating oil and wait a few minutes. Do not remove them completely yet—just loosen them enough that the flange can separate later.
  2. Support the stock exhaust. Place a jack or a block of wood underneath the muffler section to take its weight. This prevents the exhaust from dropping suddenly when you release the hangers.
  3. Remove the exhaust hangers. Each hanger is a rubber loop that hooks onto metal studs on the chassis. Using a rubber mallet, gently tap the hanger sideways while pulling downward to detach it from the stud. Alternatively, you can use a flat-blade screwdriver to pry the hanger off, but be careful not to tear the rubber. Start with the two rear hangers near the muffler, then remove the mid-pipe hangers.
  4. Separate the flange. With the hangers free, go back and fully remove the catalytic converter bolts. Pull the stock exhaust assembly down and away from the car. It may be helpful to have a second person support the muffler while you slide it out from under the bumper.
  5. Inspect and clean the mounting points. While the old system is off, check the exhaust hangers for cracks or excessive wear. If any hanger is loose or missing, replace it now. Also clean the flange face at the catalytic converter with a wire brush to ensure a good seal with the new gasket.

Installing the Borla Exhaust

The Borla exhaust is designed to be a direct replacement, but a few careful adjustments ensure a rattle-free, perfectly aligned fit.

  1. Position the new gasket. Place a new exhaust gasket over the four studs (or onto the flange face) where the mid-pipe meets the catalytic converter. Most Borla kits include a gasket; if yours does not, use a high-quality multi-layer steel gasket rated for heat cycles.
  2. Mount the Borla mid-pipe and muffler. Slide the system under the car and loosely attach the flange bolts to the catalytic converter. Hand-tighten them only—do not torque yet. This allows movement for adjusting the hanger positions.
  3. Install the exhaust hangers. Work from front to back. Hook the mid-pipe hanger onto its rubber mount, then move to the muffler section. You may need to push the rubber hangers onto the studs using a little soapy water or lubricant if they are tight. Use the rubber mallet to gently tap the hanger onto the stud until it seats fully.
  4. Adjust alignment. With all hangers loosely connected, step back and look at the exhaust tips through the rear bumper cutout. The tips should be centered left-right and level front-back. If they are off, loosen the hanger connections and shift the system. For Borla’s dual or single outlet designs, aim for an equal gap around each tip. Pushing or pulling the muffler body while the hangers are still movable can correct minor misalignments.
  5. Tighten the flange bolts. Once alignment is satisfactory, torque the catalytic converter flange bolts to factory specifications. For most Miatas, this is 30–40 ft-lbs (check the Borla instructions and your specific year). Use a torque wrench and tighten in a cross pattern to even the load.
  6. Re-tighten hanger connections. Some hanger studs have a nut or bolt that clamps the rubber hanger. Ensure those are snug but not overly tight (over-tightening can distort the rubber).

Securing and Torquing the System

Proper tightening prevents leaks, rattles, and premature wear. After the initial installation, work through the following checks:

  • Torque all metal-to-metal fasteners (flange bolts, any clamp connections) to the values specified by Borla or Mazda. For Borla systems, typical torque for flange bolts is 35 ft-lbs; for U-bolt or slip-fit connections, follow the kit instructions closely.
  • Verify exhaust clearance. Rotate the steering wheel full lock left and right while looking underneath—ensure the exhaust does not touch the sway bar, frame rails, or driveshaft. If it does, loosen the alignment and reposition the hangers slightly.
  • Check tip positioning again. After torquing, the exhaust may shift slightly. Recheck the tip alignment and correct if needed.
  • Apply anti-seize to any bolts that might need future removal (e.g., cat bolts) to ease disassembly later.

Final Checks and Test Drive

Before lowering the Miata, perform a preliminary leak and sound check. Start the engine and let it idle. Listen for any hissing or sputtering near the flange connections—this indicates an exhaust leak. A rapid “ticking” that increases with RPM often points to a leak at the header or cat joint. If you suspect a leak, shut off the engine and re-torque the bolts. You can also use a dollar bill test for slip joints: hold a piece of paper near the joint; if it flutters, there’s leakage.

While the car is still on jack stands, check for exhaust fumes under the hood or inside the cabin. Never drive with an exhaust leak inside the passenger compartment. After you’re satisfied, carefully lower the vehicle using the jack, remove the stands, and lower fully.

Take the Miata for a short test drive. Drive at varying speeds and notice any new rattles, vibrations, or drone. A properly installed Borla system should have a deep, smooth tone without metallic contact sounds. If you hear a rattle over bumps, inspect the clearance between the exhaust and the chassis. Sometimes a post-installation adjustment is needed as the system settles during the first heat cycles.

After driving 50–100 miles, re-check the flange bolt torque. The heating and cooling cycle can cause bolts to loosen slightly. Torquing again after break-in ensures a long-lasting seal.

Common Installation Pitfalls and How to Avoid Them

Misalignment of Exhaust Tips

One of the most frequent complaints is an off-center exhaust tip. This usually happens when the hangers are tightened before the system is fully aligned. Always leave the flange bolts and hanger nuts loose until you have the tips positioned exactly where you want them. If the tips still won’t center, check that the rubber hangers are not twisted or binding. In rare cases, adding a thin metal spacer behind a hanger mount can correct a persistent lean.

Rattling or Buzzing

Rattles often come from the exhaust contacting the underbody heat shield, rear sway bar, or chassis brace. Carefully inspect the area around the pipe bends—if you see any shiny wear marks, that’s the contact point. You can gently bend a heat shield away from the pipe or use a rubber isolator. Some owners add a small piece of high-temp silicone hose over a stud to dampen vibration.

Leaks at the Flange

Leaks are typically caused by a damaged gasket, uneven torque, or debris on the flange faces. Always clean both mating surfaces with a wire brush before installing the new gasket. Tighten the bolts in a star pattern, and do not rely on the gasket to seal a bent flange. If the flange on the Borla pipe appears warped, contact Borla customer service for a replacement.

Post-Installation Care and Maintenance

Borla exhaust systems are made from high-quality stainless steel that resists corrosion, but a few simple habits extend their life. Avoid spraying the exhaust with harsh chemicals when washing the car; mild soap and water are sufficient. Occasionally inspect the rubber hangers for cracks, as they degrade over time from heat and UV exposure. Re-torque the flange bolts every year or after any major off-road or track event.

If you live in a region that uses road salt in winter, consider applying a light coat of high-temperature anti-seize to the bolts and hanger studs in the fall. This prevents galling and makes future removal easier. The sound of a Borla exhaust will mellow slightly after a few hundred miles as soot builds up inside the packing.

Conclusion

Installing a Borla exhaust on your Miata is a straightforward weekend project that dramatically improves both the sound and performance of your car. By following this detailed guide—taking time to prepare, align carefully, and torque properly—you’ll achieve a perfect fit that eliminates leaks and rattles. The deep, sporty note of a Borla exhaust turns every drive into an occasion, whether you’re cruising the coast or carving canyon roads. Invest in quality tools, replacement hangers, and a new gasket, and your Miata will reward you with years of driving enjoyment. Happy driving!

For more detailed torque specs and generation-specific tips, check the Borla installation instructions or consult forums like Miata.net. For proper disposal, contact your local recycling center—many accept scrap steel mufflers.