Overview of the GR86 GReddy Exhaust Upgrade

The Subaru BRZ / Toyota GR86 platform has earned a reputation for sharp handling and balanced rear‑wheel‑drive dynamics. While the factory exhaust system delivers adequate performance for daily driving, many enthusiasts seek a more aggressive tone and modest power gains. The GReddy exhaust system is a popular aftermarket choice, offering a deep, refined sound without excessive drone. This guide provides a comprehensive, step‑by‑step installation walkthrough, covering essential tools, safety practices, and pro tips to ensure a seamless upgrade.

Before diving in, it is important to understand that modifying your vehicle’s exhaust may affect emissions compliance in some regions. Always check local regulations and consider the impact on your warranty. The GReddy system is designed as a direct fit for the 2022+ GR86 (and the second‑generation Subaru BRZ), making it a relatively straightforward DIY project for anyone with basic mechanical experience.

Tools and Materials Needed

Gathering the correct tools beforehand saves time and frustration. While the GReddy kit includes all necessary mounting hardware, you will need a standard set of hand tools and some extras.

  • GReddy exhaust system (cat‑back or axle‑back, depending on your chosen model)
  • Socket set – metric sockets (10 mm, 12 mm, 14 mm, 17 mm, 19 mm) with extensions
  • Combination wrench set – metric sizes as above
  • Torque wrench (1/2‑inch drive recommended) – needed for final tightening to manufacturer specs.
  • Jack and jack stands – a low‑profile floor jack works best
  • Penetrating oil (e.g., PB Blaster or Liquid Wrench) – essential for seized bolts
  • Rubber mallet – to gently persuade stubborn hangers or flanges
  • Safety glasses and mechanics gloves
  • Exhaust gasket – some kits supply a new gasket; if not, buy a high‑quality replacement for the flange at the catalytic converter.
  • Anti‑seize compound – for bolts that will be exposed to heat
  • Wire brush – to clean old flange surfaces

Optional but recommended: a second person to help align the rear section, a trim tool set to release rubber hangers, and a dial indicator or straight edge to check flange flatness if you notice a leak.

Benefits of the GReddy Exhaust for the GR86

The GReddy system is engineered to provide a sportier exhaust note while maintaining excellent build quality. Key advantages include:

  • Weight reduction – Typically 8–12 pounds lighter than the stock system.
  • Improved exhaust flow – Mandrel‑bent tubing reduces restriction, supporting a small gain in peak horsepower (usually 2–5 hp) and torque.
  • Aggressive but civilized sound – A deep tone with minimal interior drone at cruising speeds when paired with a resonated mid‑pipe.
  • Direct fitment – No cutting or welding required; all hangers and flanges line up with factory points.

For more technical specifications, visit GReddy’s official website. If you are sourcing the kit, Import Image Racing is a reputable US distributor that often stocks GReddy products.

Preparation Steps

Proper preparation minimizes risks and ensures a clean installation.

  1. Park the vehicle on a level surface – concrete or asphalt is ideal. Engage the parking brake and chock the front wheels.
  2. Wear safety glasses and gloves – exhaust systems accumulate road grime and sharp edges; protect your hands and eyes.
  3. Disconnect the battery – Locate the negative terminal and loosen the 10 mm nut. Move the cable away from the battery post. This prevents any accidental electrical shorts while working near the O2 sensor wiring.
  4. Let the exhaust cool completely – If the car has been driven, the exhaust can exceed 500°F. Allow at least 1–2 hours of cooldown before starting.
  5. Spray penetrating oil on all fasteners – Focus on the flange bolts (14 mm) connecting the rear pipe to the catalytic converter, and the hanger bolts/rubbers. Let the oil soak for 10–15 minutes.

Step 1: Lift the Vehicle

You need adequate clearance to slide the exhaust sections out and the new system in.

  1. Position the floor jack under the rear differential (the differential is a strong jacking point) and raise the vehicle until the rear wheels are about 12–18 inches off the ground.
  2. Place jack stands under the factory lift points, located just inside the rear tires on the chassis rail. Lower the jack carefully so the weight rests on the stands.
  3. Shake the vehicle gently to confirm it is stable. Never work under a car supported only by a jack.

If you plan to also install a front‑pipe or header, you may need to lift all four corners. For a cat‑back install, raising only the rear is sufficient.

Step 2: Remove the Stock Exhaust System

Work methodically to avoid damaging the O2 sensors or the exhaust hangers.

  1. Locate the two main flange bolts connecting the rear exhaust section to the catalytic converter (or front pipe). These are usually 14 mm hex head bolts. Spray additional penetrating oil if needed.
  2. Undo the flange bolts using a socket and breaker bar for stubborn fasteners. The factory often uses a thread‑locking compound; steady pressure will break it loose.
  3. Support the stock exhaust with a jack stand or a helper before completely removing the bolts. The system is heavy (around 30 lbs) and can drop unexpectedly.
  4. Remove the exhaust hangers. The factory uses rubber isolators that can be pried off with a trim tool or large flat‑head screwdriver. For stubborn hangers, apply a small squirt of soapy water or silicone lubricant to ease removal.
  5. Lower the stock exhaust and maneuver it out from under the car. It may be necessary to rotate the system to clear the differential and rear axle. Set the old system aside.
  6. Inspect the old gasket (the ring that seals against the catalytic converter flange). It is often crushed and should be replaced. Use a wire brush to clean the mating surface on the converter side.

Tip: If the flange bolts are severely rusted, applying heat with a small propane torch can help. Use caution near fuel lines and brake lines—never apply heat directly to a fuel component.

Step 3: Install the GReddy Exhaust System

Now the rewarding part begins. Follow the GReddy instructions included with your kit, but these general steps apply to most cat‑back systems.

  1. Test fit the new exhaust components on the ground. Most GReddy systems come in two or three sections: a mid‑pipe, a muffler section, and sometimes a tip assembly. Verify all parts are present and that the flanges are undamaged.
  2. Install a new gasket on the catalytic converter flange. Apply a thin film of anti‑seize to the new studs if supplied (or to the bolts you will reuse).
  3. Position the mid‑pipe first (if applicable). With the car lifted, slide the mid‑pipe into place, aligning the flange with the catalytic converter. Use the supplied bolts and washers, but only hand‑tighten them at this point. Do not torque yet.
  4. Attach the muffler section to the mid‑pipe flange. Again, hand‑tighten only. Ensure the muffler outlet aligns with the rear bumper cutout. The GReddy system often has an adjustable tip angle; leave the clamps loose for now.
  5. Secure the hangers. Start with the rubber hangers near the muffler. A small amount of silicone spray on the hanger posts helps them slide into the isolators. Work forward, attaching each hanger. Confirm that the exhaust pipes are not hitting the underbody, spare tire well, or the rear sway bar.
  6. Align the exhaust tips. Stand behind the car and check the gap between the tips and the bumper opening. Adjust the muffler or the tip clamps to center the tips. Tighten the tip clamp nuts (usually 10–12 mm) to GReddy’s specified torque, typically around 150–180 in‑lbs (12–15 ft‑lbs).
  7. Tighten all flange bolts to the manufacturer’s specifications. A typical torque for M10 flange bolts on a cat‑back exhaust is 30–35 ft‑lbs. Over‑tightening can warp the flange and cause leaks. Use your torque wrench and refer to the kit’s manual. For bolts without a spec, 30 ft‑lbs is a safe baseline.

Important: Some GReddy systems include a mid‑pipe with a resonator. Ensure the resonator does not contact the transmission tunnel. If it does, loosen the rear hangers and rotate the pipe slightly to create clearance.

Step 4: Final Checks

Before lowering the vehicle, inspect every aspect of the new exhaust.

  • Check all connections for leaks – Start the engine (with the car still safely on jack stands) and listen for any hissing or ticking sounds. Use your hand near each flange to feel for exhaust pulses. If you suspect a leak, tighten the flange bolts incrementally.
  • Verify clearance – With the engine idling, wiggle the exhaust to ensure it has at least 0.5 inches of clearance from any suspension components, heat shields, or the floor pan. The GR86’s rear sway bar is a common clearance point.
  • Inspect the hangers – All rubber isolators should be fully seated and not twisted. Improper hanger installation can cause the exhaust to sag over time.
  • Reconnect the battery – Attach the negative cable back to the terminal and tighten securely.

Step 5: Lower the Vehicle

Once you have cleared the checks, it is time to bring the car back down.

  1. Using the jack, lift the vehicle just enough to remove the jack stands. Work one side at a time.
  2. Slowly lower the car to the ground. Avoid dropping the jack abruptly.
  3. Remove the wheel chocks.

Step 6: Test Drive and Break‑In

The final step validates the installation and allows the system to settle.

  1. Start the engine and let it idle for 2–3 minutes while the exhaust heats up. Listen for any changes or rattles.
  2. Take the GR86 for a short test drive (5–10 minutes) under varied conditions: light throttle, moderate acceleration, and a brief highway stint to evaluate drone at 65–70 mph.
  3. Return to a safe location and re‑inspect all bolts while the exhaust is hot (use gloves). The heat can cause flanges to expand and may slightly loosen fasteners. Re‑torque if necessary after the system has cooled.
  4. Allow a break‑in period of roughly 200–300 miles for the exhaust packing to settle and the sound to mature. The tone may become deeper and the drone reduce as the system “lays down.”

If you experience a persistent check engine light (CEL) after installation, it is usually unrelated to a cat‑back exhaust unless you also changed the downpipe or front pipe. Verify all O2 sensor connections are secure. For more GR86 tuning tips, check out the GR86 Forum for community advice.

Common Installation Issues and How to Solve Them

  • Exhaust leak at the flange – Usually caused by a damaged gasket or uneven torque. Replace the gasket and tighten bolts in a cross‑pattern to 30–35 ft‑lbs.
  • Hanger won’t budge – Use silicone spray or a small pry bar. Work slowly to avoid tearing the rubber.
  • Tips rub against the bumper – Loosen the tip clamps, push the tips outward or inward as needed, then re‑tighten. If the muffler position is off, adjust the entire rear section.
  • Drone at highway speeds – Some drone is normal with aftermarket exhausts. If it is excessive, consider adding a resonator or a helmholtz chamber (some GReddy models have integrated anti‑drone tech).

Maintenance and Long-Term Care

Exhaust systems are exposed to extreme heat, moisture, and road salt. To keep your GReddy system looking and sounding good:

  • Wash the tips regularly with a quality metal polish to prevent pitting.
  • After winter driving, inspect the flanges for rust and re‑apply anti‑seize when removing or servicing.
  • Every few thousand miles, check that all hardware is still at the correct torque—especially after the first heat cycles.
  • If the exhaust develops a rattle, suspect a broken internal baffle or a dislodged heat shield. Contact GReddy support for warranty claims.

Conclusion

Installing the GReddy exhaust system on your GR86 is a satisfying upgrade that enhances both the auditory experience and performance. By following this detailed guide—paying attention to preparation, using proper tools, and performing thorough final checks—you can complete the job in a weekend afternoon. The result is a more engaging drive, a lighter exhaust note that turns heads, and a high‑quality product backed by Japanese engineering. Enjoy the soundtrack of your newly modified sports car.

For additional performance modifications, consider pairing the GReddy exhaust with a cold air intake or a tune from reputable calibrators like Open Flash Performance to fully unlock the engine’s potential.