Understanding the Benefits of a Turbo Back Exhaust for Your Subaru Forester

Upgrading to a turbo back exhaust system is one of the most effective modifications you can make to your Subaru Forester, particularly if you own a turbocharged model like the Forester XT. Unlike a cat-back or axle-back system, a turbo back exhaust replaces every component from the turbocharger outlet to the tailpipe. This includes the downpipe, mid-pipe, and rear section. By eliminating factory restrictions in the exhaust path, you reduce back pressure, improve turbo spool response, and unlock measurable horsepower and torque gains. Many owners report gains of 15 to 30 horsepower at the wheels depending on supporting modifications and tuning. Additionally, the sound profile shifts from muted and subdued to a deeper, more aggressive note that lets the signature Subaru boxer engine rumble shine through. This guide will walk you through every phase of the installation, from gathering the correct tools to performing the final leak check and test drive.

Tools and Materials Needed

Before you begin, make sure you have all necessary tools and equipment on hand. Rushing to find a missing socket or jack mid-installation is frustrating and avoidable. Below is a complete list of what you will need for this project.

  • Turbo back exhaust kit – Choose a reputable brand such as Invidia, Cobb Tuning, Grimmspeed, or HKS. Confirm the kit is designed for your specific Forester model year and engine code.
  • Socket set – Metric sockets from 8mm to 19mm, including deep well sockets for studs.
  • Wrench set – Combination wrenches in the same metric range.
  • Jack and jack stands – A low-profile floor jack and at least two sturdy jack stands rated for your vehicle weight. Never rely on the jack alone.
  • Torque wrench – Essential for tightening bolts to factory specifications without over-stressing threads.
  • Safety glasses – Protect your eyes from rust debris, penetrating oil, and falling hardware.
  • Mechanics gloves – Heat-resistant gloves help you grip oily bolts and protect your hands from sharp edges on the exhaust heat shields.
  • Penetrating oil – A high-quality product like WD-40 Specialist or PB Blaster applied well in advance makes a significant difference on rusted bolts.
  • Extension bars and universal joint – Reaching upper downpipe bolts near the turbo requires extensions and a swivel socket in many cases.
  • Exhaust gaskets – Some turbo back kits include new gaskets, but it is wise to have replacements for the turbo-to-downpipe and mid-pipe flanges.
  • Anti-seize compound – Apply to threads during reassembly to prevent future corrosion and simplify future removal.
  • Rubber mallet – Helpful for dislodging stubborn hangers or aligning flanges.

Preparation: Setting Up for Success

Proper preparation reduces installation time, prevents mistakes, and keeps you safe. Park your Subaru Forester on a level, solid surface such as a concrete garage floor or asphalt driveway. Allow the engine and exhaust system to cool completely before you begin. Working on a hot exhaust not only risks serious burns but also makes bolts and gaskets more difficult to handle. Disconnect the negative battery terminal to eliminate any risk of electrical shorts while working near the starter and oxygen sensor wiring.

If your Forester is equipped with an aftermarket oil cooler, skid plate, or under-engine covers, remove them now using the appropriate socket or screwdriver. Set these parts aside with their fasteners in a labeled zip-top bag so nothing gets lost. Place a drain pan or drip tray under the exhaust area as a precaution against residual fluid that may drip from the old system.

Applying Penetrating Oil

Spray penetrating oil generously on every exhaust bolt, nut, and stud you plan to remove. Pay particular attention to the downpipe-to-turbo nuts, the flange bolts connecting the downpipe to the mid-pipe, and the hanger bolts. Allow the oil to soak for at least 10 to 15 minutes. If you are working on a vehicle from a rust-prone region, consider applying the oil the night before and letting it work overnight. This step alone can mean the difference between a smooth removal and broken studs that require extraction later.

Step 1: Safely Lift the Vehicle

Position your floor jack under the front crossmember or reinforced pinch weld location specified in your Forester owner manual. Lift the front of the vehicle until the wheels are about 12 to 15 inches off the ground. Place jack stands under the factory lift points on the frame rails and lower the vehicle gently onto them. Give the vehicle a firm shake at each corner to confirm it is stable. For additional clearance, lift the rear of the vehicle as well and place stands under the rear subframe. You will need full under-vehicle access to remove the exhaust in one piece or to maneuver the new system into position.

Step 2: Remove the Old Exhaust System

With the vehicle secure, you can begin removing the factory exhaust. Work methodically from the turbo backward to avoid binding the system against hangers and crossmembers.

Disconnect the Oxygen Sensors

Locate the oxygen sensors mounted in the downpipe and mid-pipe sections. Use an oxygen sensor socket or a 22mm wrench to loosen them carefully. Unplug the sensor connectors from the vehicle wiring harness. On many Subaru models, the front oxygen sensor is positioned in the downpipe near the turbo, while the rear sensor is further downstream. If the sensors are stubborn, apply penetrating oil around the sensor base and allow additional soak time. Set the sensors aside in a clean location where they will not be damaged during the removal process.

Remove the Downpipe

Begin at the turbocharger outlet. Using a socket with an extension and a universal joint, access the nuts securing the downpipe to the turbo studs. These nuts are often the most challenging part of the removal due to tight clearance against the turbo housing and heat shield. Work slowly and apply controlled force to avoid snapping a stud. Once all nuts are removed, carefully separate the downpipe from the turbo flange. Lower the downpipe and maneuver it out from under the vehicle.

Remove the Mid-Pipe and Muffler Section

Work your way rearward. Remove the bolts connecting the downpipe to the mid-pipe. Support the mid-pipe with one hand as you loosen the final bolts to prevent it from dropping suddenly. Next, unbolt the mid-pipe from the center muffler or resonator section if your Forester has one. Finally, disconnect the rear muffler section from the hangers. Rubber exhaust hangers can be stubborn. Apply a small amount of soapy water or silicone lubricant to the hanger posts, then use a pry bar or a dedicated hanger removal tool to slide them off. Gently lower the entire rear section and slide it out from under the vehicle.

Inspect the Old Exhaust

Before discarding the factory system, inspect it for any signs of unusual wear, such as crushed sections from off-road impacts or rusted-through areas. This inspection can alert you to underlying issues like a failing catalytic converter or a damaged hanger bracket that needs repair before the new system goes in.

Step 3: Install the New Turbo Back Exhaust

Begin installation at the turbo and work toward the rear. This sequence ensures proper alignment and prevents the system from binding.

Install the Downpipe

Position the new downpipe under the vehicle and raise it into place. Align the flange with the turbo outlet studs. If your turbo back system includes a divorced wastegate downpipe, verify that the wastegate pathway is not interfering with any chassis or heat shield components. Hand-thread the supplied nuts onto the turbo studs. Tighten them in a cross pattern using a torque wrench set to the manufacturer specification, typically between 25 and 35 foot-pounds. Do not overtighten, as turbo studs are prone to breaking if overstressed. Reinstall the front oxygen sensor into the downpipe bung using the anti-seize compound on the threads.

Install the Cat-Delete or High-Flow Cat Section

If your turbo back system includes a separate mid-pipe section that contains a high-flow catalytic converter or a test pipe, install this next. Attach it to the downpipe flange using the provided gasket and bolts. Torque these bolts to the value specified in the kit instructions, typically around 35 to 40 foot-pounds. Ensure the exhaust path is clear of brake lines, fuel lines, and wiring harnesses.

Install the Mid-Pipe and Axle-Back Section

Connect the remaining exhaust sections one at a time. Use new gaskets at every flange connection. Do not reuse old, crushed gaskets from the factory system, as they will not seal properly and are a common cause of exhaust leaks. Hand-tighten the bolts initially to allow the system to settle into its natural position. Once all sections are loosely connected, begin final tightening from the turbo outward. Pay close attention to the clearance around the driveshaft, rear differential, and suspension components. A properly installed turbo back system should have at least 1/2 inch of clearance from any stationary part of the chassis to prevent rattling and heat transfer.

Install the Exhaust Hangers

Slide the rubber hangers onto the mounting posts on the new exhaust. This step is often easier with a small amount of lubricant or by using a hanger installation tool. Verify that each hanger is fully seated and that the exhaust is not resting directly on the hanger brackets. The hangers are designed to allow the exhaust to move slightly with engine motion. If the exhaust feels too rigid, revisit the hanger positions.

Step 4: Reconnect Oxygen Sensors and Electrical Connectors

Reinstall the rear oxygen sensor in its designated bung on the new mid-pipe or downpipe. Apply anti-seize to the threads and tighten to 25 foot-pounds. Plug both sensor connectors into the vehicle wiring harness. Secure any loose wiring with zip ties to keep it away from the hot exhaust surfaces. If your turbo back system relocates the rear oxygen sensor further downstream, ensure the wiring harness reaches without tension or contact with sharp edges.

Step 5: Check for Leaks

Start the engine and let it idle. Listen for any hissing, ticking, or puffing sounds that indicate an exhaust leak at a flange connection. If you have access to a smoke machine, that is the most accurate way to identify small leaks. Alternatively, carefully run your gloved hand around each joint while the exhaust is cool enough to touch. Do not use your bare skin. If you detect a leak, shut the engine off, allow the system to cool, and tighten the flange bolts incrementally. For persistent leaks, inspect the gasket for proper alignment and consider replacing it with a new gasket.

Cycle the Throttle and Listen

After the initial idle check, have a helper briefly rev the engine to 2000 to 3000 RPM while you listen for leaks under load. Exhaust leaks often manifest more audibly when the system is under pressure. Monitor the exhaust note for any abnormal rattles or contact with the chassis. If you hear a metallic buzz or clank, the exhaust is likely contacting a heat shield or a suspension component. Adjust the position of the affected section slightly and retighten the hangers and clamps.

Final Steps

Once you have confirmed the system is leak-free and the engine is idling smoothly, turn the engine off. Allow the exhaust to cool completely before performing the final tightening of all clamps and bolts. Retorque every flange connection with a torque wrench to ensure consistent clamping force. Reinstall any heat shields, skid plates, or under-engine covers you removed earlier. Connect the negative battery terminal.

Lower the vehicle from the jack stands by raising it slightly with the floor jack, removing the stands, and then slowly lowering the vehicle to the ground. Before driving, do a final walkaround underneath the vehicle to confirm nothing is loose or hanging near the ground.

Performance Expectations and Considerations

After installation, you will immediately notice a more aggressive exhaust tone, particularly during cold start and under hard acceleration. The turbo spool is likely to become audible sooner in the RPM range, often referred to as spool chatter or whistle. Depending on your specific turbo back configuration, expect a power increase of 15 to 30 wheel horsepower after tuning. If your Forester is equipped with a factory tune, the engine control unit may need recalibration to fully benefit from the reduced exhaust restriction. Running a turbo back system without a tune on a modern Subaru can sometimes trigger a check engine light due to changes in back pressure and oxygen sensor readings. A professional dyno tune or an updated ECU flash from a reputable tuner is strongly recommended to maximize performance and reliability.

Maintenance Tips for Your New Turbo Back Exhaust

A turbo back exhaust system is a durable upgrade, but it requires routine attention to stay in top shape. Follow these maintenance recommendations to extend the life of your investment.

  • Inspect flanges and hangers monthly. Bolts can loosen over time from thermal cycles. Recheck torque on all flange bolts after the first 500 miles of driving.
  • Watch for corrosion. If your Forester sees winter roads treated with salt, wash the underside regularly. Many turbo back systems use stainless steel, but salt and moisture can still cause surface rust on welds and hardware.
  • Clean the exhaust tips. Use a stainless steel cleaner or a mixture of baking soda and water to remove carbon buildup and road grime from the tips. Regular cleaning preserves the appearance and prevents pitting.
  • Monitor engine performance. Pay attention to changes in exhaust tone, fuel economy, or acceleration. A sudden increase in volume or a rattling sound may indicate a failed hanger, a loose heat shield, or a gasket leak.
  • Check oxygen sensor function. If your check engine light illuminates, scan the code immediately. A faulty oxygen sensor can cause poor air-fuel mixture and reduce the benefits of your turbo back system.

Conclusion

Installing a turbo back exhaust on your Subaru Forester is a highly rewarding hands-on project that transforms both the sound and performance of your vehicle. By following this step-by-step guide, you can complete the installation with confidence, avoid common pitfalls like broken studs or persistent leaks, and enjoy the full benefits of reduced back pressure and quicker turbo response. Whether you are pursuing a weekend project or building a dedicated performance Forester, this upgrade is a foundational step that pairs well with a quality intake and a professional engine tune. Take your time, work safely, and enjoy the enhanced driving experience your new turbo back exhaust delivers.

For more information on compatible exhaust systems and tuning resources, consider exploring forums like SubaruForester.org or consulting a professional shop that specializes in Subaru performance modifications. Additional technical references can be found through Subaru's factory service manuals or aftermarket suppliers such as Cobb Tuning and Grimmspeed, who offer detailed installation documentation and customer support for their products.