Step-by-Step Guide to Installing a Perrin Intercooler on the FA20 Subaru

Upgrading the intercooler on your FA20 Subaru is one of the most effective bolt-on modifications for increasing horsepower and improving engine reliability. The FA20 engine, found in models like the Subaru BRZ, Toyota GR86, and Scion FR-S, is known for its eager nature but also for generating significant intake air temperatures under load. The factory intercooler, while adequate for stock power levels, becomes a bottleneck once you add a tune, downpipe, or other performance parts.

The Perrin Intercooler is a popular aftermarket choice because it offers a larger core volume, better fin density, and improved flow characteristics compared to the stock unit. This translates to lower intake temperatures, denser air charge, and more consistent power delivery. This guide walks through the entire installation process in detail, from gathering tools to performing final checks, so you can complete the swap with confidence.

Tools and Materials Needed

Having everything ready before you start will make the installation smoother and prevent frustrating trips back to the toolbox. Here is the full list of tools and materials you will need:

  • Perrin Intercooler Kit – Includes the intercooler core, silicone couplers, T-bolt clamps, and all necessary hardware. Verify kit contents against the included inventory list.
  • Socket Set – Metric sockets from 8mm to 17mm. A 10mm, 12mm, and 14mm socket will be used most often.
  • Wrench Set – Combination wrenches in the same metric sizes, especially for tight spaces where a socket cannot reach.
  • Torque Wrench – A 1/2" drive torque wrench capable of reading 10–50 ft-lbs for critical fasteners like the intercooler mounting bolts.
  • Flathead Screwdriver – For prying loose hose clamps and gently releasing electrical connectors.
  • Phillips Screwdriver – For removing plastic trim pieces and air box covers.
  • Ratchet Extensions – A 3-inch and a 6-inch extension will help reach bolts buried deep in the engine bay.
  • Hose Clamps – The kit comes with T-bolt clamps, but having a few extra worm-gear clamps in 2.5" and 3" sizes is handy.
  • Intercooler Piping – The Perrin kit usually includes mandrel-bent aluminum or stainless steel piping. Check that all pipes are present.
  • Heat Resistant Gloves – The engine bay can be hot, and sharp edges on intercooler cores are common.
  • Shop Towels – For wiping oil residue, coolant drips, or dirt from mating surfaces.
  • Jack and Jack Stands – Optional but recommended for better access to the lower intercooler piping.
  • Safety Glasses – Debris can fall into eyes when working under the car.
  • Penetrating Oil – Useful if any bolts are rusted or seized.

Preparation Steps

Proper preparation reduces the risk of mistakes and ensures a clean working environment. Follow these steps before touching any hardware:

  • Park the vehicle on a flat, level surface and engage the parking brake. Chock the rear wheels to prevent any movement.
  • Disconnect the negative battery terminal using a 10mm wrench. This prevents accidental short circuits and resets the ECU so it can adapt to the new hardware.
  • Allow the engine to cool completely if it has been running. The intercooler and surrounding components can retain heat for 30–60 minutes. A cool engine also makes removing hoses easier and safer.
  • Remove any engine covers or trim pieces that obstruct access to the intercooler. On the FA20, this often includes the plastic engine cover and the upper radiator shroud.
  • Take reference photos of the stock intercooler and piping layout. These photos will help you remember how hoses and clamps were oriented during reassembly.

Understanding the FA20 Engine and Intercooler System

The FA20 is a 2.0-liter horizontally opposed (boxer) four-cylinder engine that uses a twin-scroll turbocharger in factory turbo applications like the Subaru Levorg or aftermarket turbo kits. However, the naturally aspirated FA20 in the BRZ/FR-S also benefits from intercooler upgrades when paired with forced induction. The Perrin intercooler is designed to work with both factory turbo configurations and aftermarket supercharger or turbo setups.

The stock intercooler on the FA20 is a bar-and-plate design with moderate core thickness. While it works well at low boost levels, heat soak occurs quickly during spirited driving or track sessions. The Perrin unit features a larger core volume and improved fin design that sheds heat more efficiently. This means intake air temperatures remain lower, allowing the engine to maintain timing advance and produce more consistent power.

For more background on intercooler theory and how core size affects performance, check out this detailed explanation from Car Throttle.

Removing the Stock Intercooler

Removing the factory intercooler is straightforward, but you need to be methodical to avoid damaging hoses or sensors. Work slowly and label any connectors you disconnect.

Step 1: Access the Intercooler Area

The stock intercooler is located at the front of the engine bay, sandwiched between the radiator and the engine block. On FA20 applications, you may need to remove the upper grille or front bumper cover for better access, depending on your specific vehicle model. For the BRZ/FR-S, the intercooler is visible once the plastic shroud is removed.

Step 2: Disconnect the Intake Ducting

Using a flathead screwdriver, loosen the hose clamps securing the intake duct to the throttle body and the air box. Carefully pull the ducting aside. You do not need to fully remove the air box, but having it loose gives you more room to work.

Step 3: Unbolt the Stock Intercooler

Locate the bolts that secure the intercooler to the core support or radiator crossmember. On most FA20 installations, there are four to six bolts. Use a 12mm socket and ratchet with an extension to remove them. Keep these bolts in a labeled bag; you may reuse them if the Perrin kit does not include replacements.

Step 4: Disconnect Intercooler Hoses

The intercooler is connected to the turbocharger (or compressor outlet) and the throttle body via silicone or rubber hoses. Loosen the clamps at both ends of each hose using a flathead screwdriver or a 7mm nut driver. Gently twist and pull the hoses free. If they are stuck, use a small pry bar or a flathead screwdriver wrapped in a shop towel to break the seal.

Step 5: Remove the Intercooler Assembly

With all hoses disconnected and bolts removed, lift the intercooler straight up and out of the engine bay. The stock unit is relatively light, but be careful not to drop it or let it scrape against the radiator fins. Set it aside on a clean surface.

Installing the Perrin Intercooler

Now that the factory intercooler is out, you can install the Perrin unit. The Perrin kit is designed to be a direct bolt-on replacement, meaning no drilling, cutting, or permanent modifications are required. However, you must pay careful attention to hose routing and clamp torque.

Step 1: Prepare the Mounting Surface

Clean the intercooler mounting area with a shop towel to remove any dirt, oil, or debris. Check the rubber isolation mounts on the core support; if they are worn or missing, replace them before installing the new intercooler.

Step 2: Position the Perrin Intercooler

Lower the Perrin intercooler into the engine bay, aligning the mounting tabs with the factory mounting points. The intercooler should sit level and squarely against the core support. Do not force it; if it does not align, check that no hoses or wires are caught underneath.

Step 3: Secure the Intercooler Mounting Bolts

Thread the bolts into the mounting holes by hand to avoid cross-threading. Once all bolts are started, tighten them in a crisscross pattern to the torque specification included in the Perrin instructions (typically 15–20 ft-lbs). Do not overtighten, as this can damage the intercooler core or crack the mounting brackets.

Step 4: Attach the Intercooler Piping

The Perrin kit includes polished aluminum piping that replaces the factory rubber hoses. Slide the silicone couplers onto the ends of the pipes, then position the pipes so they connect the turbo outlet to the intercooler inlet, and the intercooler outlet to the throttle body. Use the T-bolt clamps provided in the kit to secure each connection.

  • Turbo-to-Intercooler Pipe: This pipe carries hot compressed air from the turbo to the intercooler. Ensure the pipe clears the fan shroud and does not rub against any moving parts.
  • Intercooler-to-Throttle Body Pipe: This pipe routes cooled air to the engine. It should have a smooth curve with no kinks.
  • Bypass Valve or Blow-Off Valve: If your Perrin kit includes a provision for a bypass valve, install the valve and its associated vacuum line now.

Step 5: Reconnect Sensors and Hoses

If you disconnected any sensors, such as the intake air temperature sensor or boost reference line, reconnect them now. Make sure the wiring harness is clear of hot surfaces and moving parts.

Step 6: Double-Check All Connections

Go over every clamp, bolt, and hose connection. Use a torque wrench on the clamps to ensure they are snug but not so tight that they cut into the silicone couplers. Verify that the intercooler piping does not contact the hood liner or radiator fan when the engine is running.

Final Checks and Testing

After the physical installation is complete, perform these checks to ensure everything is safe and functional before driving.

Reconnect the Battery and Inspect for Leaks

Reconnect the negative battery terminal and tighten it to 8 ft-lbs. Start the engine and let it idle. Listen for any hissing sounds that indicate an air leak. A quick way to check is to spray a small amount of soapy water on each connection; if bubbles appear, you have a leak that needs to be addressed.

Check for Codes and Sensor Readings

Using an OBD2 scanner, check for any fault codes. Also monitor the intake air temperature (IAT) sensor reading. After a minute of idling, the IAT should be near ambient. If it is significantly higher, check for a post-intercooler leak or a misrouted hose.

For more information on interpreting OBD2 data from the FA20, refer to this comprehensive thread on FT86 Club.

Test Drive

Take the vehicle for a test drive under varying conditions: light throttle, moderate acceleration, and a few full-throttle pulls. Pay attention to boost response and any unusual noises. The Perrin intercooler should provide a noticeable improvement in throttle response and reduce heat soak. If you feel a loss of power or hear a loud whooshing sound, check for a loose clamp or a disconnected hose.

Consider a Tune

While the Perrin intercooler works with a stock ECU, you will maximize its benefits with a custom tune. An ECU tune can take advantage of the lower intake temperatures by adding timing and boost. Companies like Perrin Performance offer tuning recommendations for their intercoolers. Always verify that your tune is compatible with your specific fuel and altitude conditions.

Maintenance Tips for the Perrin Intercooler

Keeping your intercooler in top condition ensures long-term performance. Here are a few maintenance practices to follow:

  • Inspect the intercooler core for bent fins or debris buildup every oil change. Use a fin comb to straighten bent fins and a soft brush to remove bugs or dirt.
  • Check hose clamps for tightness after the first 500 miles. Silicone couplers can compress slightly, causing clamps to loosen.
  • Watch for oil residue inside the piping. A small amount of oil blow-by is normal, but excessive oil may indicate a failing turbo seal or PCV system issue.
  • Clean the intercooler annually with a gentle degreaser and a low-pressure water rinse. Avoid using pressure washers directly on the fins, as they can bend them.

For a deeper dive into intercooler maintenance and how to diagnose common issues, read this guide from Subaru Performance Parts.

Conclusion

Installing a Perrin intercooler on your FA20 Subaru is a rewarding upgrade that delivers genuine performance gains. The process is well within the reach of a home mechanic with basic hand tools and a methodical approach. By following this step-by-step guide, you have removed the restrictive stock intercooler, installed the larger Perrin unit, and verified that all connections are secure and leak-free.

The result is an engine that breathes more easily, runs cooler under boost, and maintains power even during extended driving sessions. Whether you are building a track car or simply want a more responsive daily driver, the Perrin intercooler is a solid investment. Pair it with a proper tune and supporting modifications, and your FA20 will reward you with consistent, reliable performance mile after mile.

For additional installation tips and to browse related upgrades, visit FT86 Speed Factory for a wide selection of FA20 performance parts.