Introduction to the Forge Motorsport 27-Inch Intercooler Upgrade

Upgrading the intercooler on your Subaru WRX is one of the most effective modifications for reducing intake air temperatures and increasing horsepower. The Forge Motorsport 27-inch intercooler is a direct-fit replacement that offers a larger core volume and bar-and-plate construction for superior heat dissipation compared to the factory tube-and-fin unit. This guide will walk you through every step of the installation process, from workspace preparation to final test driving. By the end, you’ll have a rugged, high-performance intercooler that supports your WRX’s turbocharged engine under spirited driving or track conditions.

Before you begin, note that this installation assumes you are mechanically inclined and have basic experience working on Subaru vehicles. If you’re uncertain about any step, consult a professional mechanic or refer to your WRX’s service manual. The tools and parts listed below will make the job straightforward and safe.

Tools and Materials Needed

Having everything ready before you start prevents frustration and wasted time. Below is a complete list of what you’ll need. Use only high-quality hardware; torque specifications are critical for metal components.

  • Forge Motorsport 27-inch intercooler – includes the core, silicone couplers, mounting brackets, and all necessary fasteners
  • Socket set – metric sockets in 8mm, 10mm, 12mm, 14mm, and 17mm (preferably deep sockets)
  • Wrench set – combination wrenches for tight spaces (10mm, 12mm, 14mm)
  • Screwdriver set – flathead and Phillips head for bumper clips and harness connectors
  • Torque wrench – capable of 10–50 ft-lb range (calibrated if possible)
  • PTFE thread sealant – recommended for boost/vacuum fittings (optional but helpful)
  • Silicone lubricant – for easing coupler installation onto intercooler openings
  • Safety glasses and gloves – protect against sharp edges, coolant, and debris
  • Jack and jack stands or ramps – for improved access if needed
  • Shop towels and isopropyl alcohol – for cleaning mating surfaces

If your WRX is equipped with aftermarket charge pipes or a front mount conversion, note that this installation assumes a stock location replacement. Always verify compatibility with Forge’s product fitment guide.

Preparation: Workspace and Vehicle Setup

A clean, well-lit workspace reduces the risk of losing hardware or damaging components. Park the WRX on a level surface and allow the engine to cool completely – the stock intercooler and piping can retain heat and pressure. Disconnect the negative battery terminal to avoid accidental electrical shorts. If you plan to drain any coolant that might be present in the intercooler lines, place a catch pan under the vehicle.

Inspect the stock intercooler for any existing damage or loose brackets. Take photos of the factory hose routing and clamp positions before disassembly – this will help during reassembly, especially if you’re reusing any factory hoses alongside the new silicone couplers.

You may also want to raise the front of the car using ramps or jack stands to make accessing the lower bumper fasteners easier. This step is optional but recommended if you are not comfortable working from a low stance.

Step 1: Remove the Front Bumper

Removing the front bumper on a WRX (GD, GH/GR, VA chassis) requires careful handling of plastic clips and wiring harnesses. The process is similar across generations, but check your specific year’s service manual for exact fastener locations.

Locate and Remove Fasteners

  • Open the hood and remove the upper grille screws (typically 8mm or screw clips) along the top edge of the radiator support.
  • Under the bumper, near the wheel wells, remove the lower push clips or screws securing the bumper to the fender liners.
  • At the sides, near the headlight housings, remove the screws and plastic rivets holding the bumper against the fenders.
  • If your WRX has fog lights, disconnect the wiring harness plugs before pulling the bumper forward.

Detach Wiring and Remove Bumper

  • Disconnect any wiring harnesses attached to the bumper: fog lights, headlight washers (if equipped), and ambient temperature sensor (located near the lower grille).
  • Pull the bumper cover outward gently, starting at the top corners – avoid snapping the tabs that hold the grille in place.
  • Set the bumper aside on a soft surface to prevent scratching the paint. If you need to remove it fully, have an assistant help you to avoid damaging the clips.

Tip: Place the removed fasteners in a magnetic tray or labeled bag. It is easy to mix up the different screw lengths, which can cause headaches during reinstallation.

Step 2: Remove the Stock Intercooler

With the bumper removed, the stock intercooler is accessible. It sits directly in front of the radiator and is held by two brackets and four hoses (two intake, two outlet).

Disconnect Hoses and Wiring

  • Loosen the hose clamps on both sides of the intercooler using a nut driver or screwdriver. Factory clamps are usually spring-type; use pliers to compress them and slide them back.
  • Disconnect the recirculation valve hose (if your WRX uses a bypass valve mounted near the intercooler).
  • Unplug any sensor connectors (boost pressure sensor, intake air temperature sensor) that may be attached to the intercooler or its piping.

Unbolt and Remove

  • Use a socket or wrench to remove the three bolts on each mounting bracket (usually 12mm). Some later WRX models have integrated brackets – note which bolts go where.
  • Carefully lift the stock intercooler upward. It may be stuck due to silicone residue – gently wiggle it free. Do not force it against the radiator fins.
  • Place the removed intercooler aside. Inspect its condition – if you plan to sell it, clean the fins and check for any damage.

Note: The stock intercooler can be heavy (approx. 15–18 lbs). Support it firmly while disconnecting the lower hoses to avoid dropping it and damaging the radiator.

Step 3: Install the Forge Motorsport Intercooler

The Forge 27-inch intercooler is a direct-fit but requires attention to detail during installation. Its bar-and-plate core is thicker than the stock unit, so bracket alignment is key.

Prepare the Mounting Area

  • Clean the metal contact points on the radiator support where the new brackets will sit. Use isopropyl alcohol to remove any grease or dirt.
  • Apply PTFE thread sealant to the bolt threads if you want extra vibration resistance – otherwise, use the provided lock washers.

Position and Secure the Intercooler

  • Lower the Forge intercooler into the engine bay, aligning the mounting brackets with the existing holes on the radiator core support.
  • One person can hold the intercooler in place while a second person starts the bolts (do not fully tighten until all bolts are in).
  • Tighten the bolts to 15–20 ft-lb – overtightening can strip the threads or deform the brackets.

Connect Silicone Couplers and Hoses

  • Slide the silicone couplers over the intercooler ends first. Use a small amount of silicone lubricant to ease the process. Do not use grease or oil that can attack the rubber.
  • Attach the factory or aftermarket charge pipes to the opposite ends of the couplers. Ensure the hoses are seated fully – a gap of even 1/4 inch can cause a boost leak.
  • Position the t-bolt or worm-gear clamps over the coupler ends (about 1/4 inch from the rim) and tighten evenly to 10–12 ft-lb using a torque wrench. Over-tightening can cut the silicone.
  • Reconnect the recirculation valve hose and any sensor connectors. Double-check that the wiring is routed away from the hot turbo housing.

Pro tip: The Forge intercooler has a larger core volume. If your vehicle uses a bypass valve that was located on the stock intercooler, you may need an adapter or a relocation kit – verify fitment before installation. Most WRX models retain the factory bypass valve location on the intake manifold, so this is rarely an issue.

Step 4: Check for Leaks

Before reinstalling the bumper, you must pressure-test the intake system for leaks. Even a small leak can result in poor throttle response, high intake temperatures, and potential engine damage.

Simple Idle Check

  • Reconnect the battery terminal and start the engine. Allow it to idle for one minute.
  • Listen for hissing sounds around the couplers, intercooler connections, and sensor ports. Use a stethoscope or a piece of hose held to your ear to pinpoint subtle leaks.
  • Inspect all clamping areas for signs of soapy bubbles – spray a mix of water and dish soap around the joints.
  • If you have a boost leak tester (available from most tuning tool retailers), cap the intake system and apply 15–20 psi of compressed air.
  • Monitor the pressure gauge – a drop of more than 1 psi per minute indicates a leak.
  • Fix leaks by tightening clamps or repositioning hoses. Replace any damaged O-rings on sensor connectors.

For a detailed tutorial on building a boost leak tester, check out this IWSTI DIY guide. Performing this test now saves you from having to remove the bumper again later.

Step 5: Reinstall the Front Bumper

Once you’re confident there are no leaks, proceed with reinstalling the bumper. Patience is critical – plastic clips can break easily if forced.

  • Reconnect all wiring harnesses (fog lights, ambient sensor, etc.) before placing the bumper back on. Test fog lights briefly before final assembly.
  • Align the bumper’s lower mounts first, then push the top tabs into the grille area. The bumper should snap into place with a firm push – do not use force if it resists; check for obstructions.
  • Install the screws and clips in the following order: upper grille screws, side fender screws, lower underbody screws. Tone is important: tighten until snug, but avoid stripping the plastic threads.
  • Check that the bumper’s clearance around the intercooler is even – you may need to adjust the intercooler brackets slightly if the bumper is rubbing against the core.

Tip: Replace any broken plastic clips with OEM equivalents. You can find them at your local Subaru dealer or online parts retailers like Subaru Parts Online.

Step 6: Final Checks and Test Drive

Now you’re ready to verify the installation under real driving conditions.

Cold Start Inspection

  • Start the engine from cold and let it reach operating temperature. Monitor the intake air temperature (IAT) sensor readings using an OBD2 scanner if available.
  • Check that the engine does not idle roughly or surge – a large boost leak can cause idle issues.
  • Turn off the engine and re-check the tightness of all clamps and bolts after the first heat cycle (expansion and contraction can loosen them).

Road Test

  • Take the WRX for a short drive at low speeds (under 35 mph) and then gradually build boost in 3rd gear. Listen for boost leaks – a distinct high-pitched whistle or hiss indicates a problem.
  • Perform two or three full throttle pulls from 2,500 to 5,500 rpm in a safe location. The air charge should remain cool – your IATs should drop compared to the stock intercooler under similar conditions.
  • Monitor for any engine knock or knock feedback if you have a tuning device. Lower IATs reduce knock potential, but if you made significant power increases, a custom tune is recommended.

If everything appears normal, you have successfully installed your Forge Motorsport 27-inch intercooler. For optimal performance, consider upgrading the charge pipes and recirculation valve simultaneously – see Forge Motorsport’s official installation guides for additional recommendations.

Conclusion: Enjoy the Benefits of a Cooler, More Responsive WRX

Installing a Forge Motorsport 27-inch intercooler is a rewarding project that yields tangible performance gains: lower intake air temperatures, reduced heat soak, and increased horsepower potential. The bar-and-plate core construction also provides excellent durability compared to the stock intercooler, making it a long-term upgrade for daily-driven or track-focused WRXs.

To get the most out of your new intercooler, pair it with a proper engine tune (e.g., from Cobb Tuning or OpenECU) that accounts for the increased airflow. Regularly inspect your intercooler’s mounting brackets and hoses during routine maintenance – silicone couplers can degrade after 30,000+ miles. If you encounter any issues during installation, consult the Subaru owner support page or an experienced WRX forum community for adive.