Upgrading your Subaru WRX with a cat-back exhaust system is one of the most popular modifications among enthusiasts seeking enhanced performance, improved exhaust tone, and a sportier aesthetic. A cat-back exhaust replaces the section of the exhaust system from the catalytic converter back to the rear of the vehicle, allowing for better exhaust flow and a more aggressive sound without affecting emissions compliance. This comprehensive guide will walk you through the process of installing a cat-back exhaust on your Subaru WRX safely and efficiently, providing detailed explanations, tips, and troubleshooting advice to ensure a successful upgrade.

Understanding the Benefits of a Cat-back Exhaust

Before diving into the installation process, it’s important to understand why a cat-back exhaust is a valuable upgrade for your Subaru WRX:

  • Performance Gains: By reducing exhaust backpressure, a cat-back system can help your turbocharged WRX breathe more freely, potentially increasing horsepower and torque.
  • Enhanced Sound: Cat-back systems often provide a deeper, more aggressive exhaust note that enhances the driving experience without being excessively loud or intrusive.
  • Weight Reduction: Many aftermarket cat-back exhausts are made from lighter materials such as stainless steel or titanium, reducing overall vehicle weight.
  • Visual Appeal: Upgraded exhaust tips and polished piping can give your WRX a sportier and more refined look.
  • Durability: High-quality cat-back systems resist corrosion better than stock exhausts, offering longer lifespan.

Tools and Materials Needed

Gathering all necessary tools and materials before starting the installation will save time and prevent interruptions. Here’s a detailed list of what you’ll need:

  • Socket Set and Ratchet: Metric sizes commonly used on Subaru exhaust components (10mm, 12mm, 14mm, 17mm, etc.)
  • Torque Wrench: To tighten bolts to manufacturer specifications, ensuring proper seal and preventing damage.
  • Jack and Jack Stands: A sturdy hydraulic jack and quality jack stands to safely elevate and support the vehicle.
  • WD-40 or Penetrating Oil: To loosen rusted or seized bolts and nuts.
  • New Cat-back Exhaust System: Ensure compatibility with your WRX model year and trim.
  • Exhaust Hanger Removal Tool or Flat-Head Screwdriver: For prying exhaust hangers free without damage.
  • Rubber Mallet: Useful for gently tapping components into place.
  • Gloves and Safety Goggles: To protect your hands and eyes during the process.
  • Anti-Seize Compound: To apply on bolts during reassembly preventing future rusting and seizing.
  • New Exhaust Gaskets (if required): Some systems or vehicle models may require fresh gaskets for a proper seal.
  • Shop Towels or Rags: For cleanup and handling greasy parts.

Preparation and Safety Considerations

Proper preparation ensures safety and a smooth installation:

  • Work Area: Choose a flat, level surface with adequate lighting and ventilation. Avoid working on a slope or in confined spaces.
  • Vehicle Cool Down: Make sure the exhaust system is completely cool before starting to avoid burns.
  • Protective Gear: Always wear gloves to protect your hands from sharp edges and goggles to shield your eyes from debris.
  • Jack Placement: Consult your WRX owner’s manual for recommended jacking points. Using improper points can damage the vehicle or cause instability.
  • Secure the Vehicle: Once lifted, use jack stands to securely hold the vehicle. Never rely solely on a hydraulic jack.

Step-by-Step Removal of the Stock Exhaust

Removing the factory exhaust requires patience and care to avoid damage to adjacent components:

1. Inspect the Exhaust System

Before removal, examine the stock exhaust for rusted bolts, damaged hangers, or other issues that could complicate removal. Spray penetrating oil on all bolts, clamps, and hangers, focusing on the areas where the exhaust connects to the catalytic converter and mid-pipe.

2. Loosen Exhaust Clamps and Bolts

Using the socket set and ratchet, begin loosening the bolts that connect the exhaust system from the catalytic converter back. These are typically secured with clamps or flange bolts. Take your time and apply more penetrating oil if bolts are stubborn.

3. Remove Exhaust Hangers

The exhaust is suspended from rubber hangers attached to the chassis. Use an exhaust hanger removal tool or a flat-head screwdriver to gently pry the hangers free. Supporting the exhaust pipe with one hand while removing hangers can prevent the system from dropping suddenly.

4. Detach the Exhaust System

Once all bolts and hangers are free, carefully lower the exhaust system. Having a helper can make this step easier and safer. Place the old exhaust aside for recycling or disposal according to local regulations.

Installing the New Cat-back Exhaust System

With the old system removed, you are ready to install the new cat-back exhaust:

1. Inspect New Components

Unpack the new exhaust and check all parts against the manufacturer’s checklist. Verify pipe diameters, flange types, and hardware completeness.

2. Test-Fit the System

Before final assembly, loosely fit the cat-back exhaust to the vehicle, aligning all mounting points and hangers. This allows you to identify any fitment issues early.

3. Attach Exhaust Hangers

Begin by sliding the exhaust hangers into the rubber mounts on the chassis. This supports the exhaust weight and ensures proper positioning.

4. Connect to Catalytic Converter

Secure the front section of the cat-back exhaust to the existing catalytic converter or mid-pipe flange. Use new gaskets if required and apply anti-seize to bolts. Tighten bolts snugly but leave final torque adjustment until the full system is in place.

5. Tighten Clamps and Bolts

Once the exhaust is properly aligned and hangers are supporting the system, tighten all clamps and bolts to the manufacturer’s recommended torque specifications. Proper torque ensures a leak-free joint and prevents damage.

6. Check for Clearance

Ensure the exhaust pipes have adequate clearance from the underbody, suspension components, and heat-sensitive parts. Use a rubber mallet to adjust positioning if necessary.

Post-Installation Checks and Break-in Procedure

After installation, it’s essential to verify the system’s integrity and performance:

1. Inspect for Leaks

Start the engine and let it idle. Listen closely for any exhaust leaks, which may sound like hissing or popping near joints. If leaks are detected, carefully re-tighten bolts or clamps.

2. Heat Cycle the Exhaust

Allow the vehicle to run until the exhaust reaches operating temperature, then let it cool. This heat cycle helps components settle and can reveal any loosening or leaks.

3. Test Drive

Take a short test drive, varying engine speed and load. Monitor for rattles, vibrations, or unusual noises. After the drive, recheck all fasteners.

4. Re-Torque Bolts

After the heat cycle and test drive, it’s a good practice to re-torque all bolts to ensure nothing has loosened.

Maintenance and Troubleshooting

To keep your new cat-back exhaust in optimal condition, consider these tips:

  • Regular Inspections: Periodically check for loose clamps, rust spots, or damaged hangers.
  • Cleaning: Clean polished or chrome exhaust tips to maintain appearance using appropriate metal polish.
  • Noise Changes: If you notice sudden changes in exhaust sound, inspect for leaks or damage.
  • Rust Prevention: Applying high-temperature exhaust paint or coatings can extend system life, especially in regions with road salt.
  • Professional Assistance: If you encounter persistent leaks or fitment problems, consult a professional mechanic or exhaust specialist.

Additional Upgrades and Considerations

Installing a cat-back exhaust can be the foundation for further performance enhancements on your Subaru WRX:

  • Upgraded Downpipe: Replacing the downpipe along with a cat-back can significantly improve exhaust flow and turbo response.
  • ECU Tuning: After upgrading the exhaust, consider a custom ECU tune to optimize air/fuel ratios and maximize power gains.
  • Intake Upgrades: Pairing the cat-back with a high-flow intake system further enhances performance gains.
  • Suspension and Wheels: Complement your exhaust upgrade with handling enhancements for a well-rounded driving experience.

Common Questions About Cat-back Exhaust Installation

Will a Cat-back Exhaust Affect My Subaru WRX’s Warranty?

Most manufacturers do not void your entire vehicle warranty due to a cat-back exhaust installation, as it does not affect emissions components like the catalytic converter. However, any damage directly resulting from the aftermarket exhaust may not be covered. It’s advisable to check with your dealer or manufacturer for specific warranty details.

Can I Install the Cat-back Exhaust Myself or Should I Seek Professional Help?

If you are comfortable working with automotive tools and following instructions carefully, installing a cat-back exhaust is a manageable DIY project. However, if you lack experience or proper equipment, consulting a professional can ensure precise fitment and avoid potential issues.

How Long Does the Installation Typically Take?

For an experienced DIYer, installation can take approximately 1.5 to 3 hours, depending on tools, rust condition, and vehicle model year. First-time installers should allocate extra time.

Will Installing a Cat-back Exhaust Improve My Fuel Economy?

While a cat-back exhaust primarily improves power and sound, some drivers notice slight improvements in fuel efficiency due to better engine breathing. However, the effect is usually modest and depends on driving style.

Conclusion

Installing a cat-back exhaust on your Subaru WRX is an exciting upgrade that combines performance, sound, and style improvements. By carefully preparing, following step-by-step instructions, and double-checking your work, you can achieve a professional-quality installation in your own garage. Remember to prioritize safety, use quality tools, and take your time to ensure the best results. Once installed, enjoy the enhanced exhaust note and the invigorated driving experience that your WRX deserves.