Upgrading Your 2018 WRX with the Turbosmart Top Mount Intercooler

If you drive a 2018 Subaru WRX, you already know the FA20DIT engine delivers solid turbocharged power from the factory. But as boost levels rise and intake air temperatures climb, the factory top mount intercooler becomes a bottleneck. Replacing it with the Turbosmart Top Mount Intercooler is one of the most effective bolt-on upgrades for reducing heat soak, increasing charge air density, and unlocking consistent horsepower. This guide walks you through every step of the installation, from preparation to final leak checks. Whether you are a first-time installer or a seasoned enthusiast, these instructions will help you get the job done safely and accurately.

Why Upgrade the Intercooler on a 2018 WRX?

The factory intercooler on the 2018 WRX is designed for moderate boost levels and mild driving. Under hard acceleration or during summer track days, it quickly becomes heat-soaked, causing intake air temperatures to spike and the ECU to pull timing. The Turbosmart unit features a larger bar-and-plate core with increased internal volume and better fin density. This allows for more efficient heat rejection, lower pressure drop, and sustained power during repeated pulls. Pairing this intercooler with a quality tune or accessport can yield gains of 15 to 25 wheel horsepower on pump gas.

Tools, Parts, and Safety Prep

Before you start disassembling the engine bay, gather everything you need. Working on a hot engine or without the right tools can lead to damage or injury. Set aside a few hours for this job if it is your first time.

Required Tools

  • Metric socket set (8mm, 10mm, 12mm, 14mm, 17mm)
  • Torque wrench (capable of 5-50 ft-lb range)
  • Flathead screwdriver (medium tip)
  • Phillips screwdriver (#2)
  • Ratchet extension (6 inch and 12 inch)
  • Pry tool or trim removal tool for hose clamps
  • Shop towels or rags
  • Safety glasses and gloves
  • Penetrating oil (if bolts are seized)
  • Coolant funnel (if you plan to flush or top off coolant)

Parts and Supplies

  • Turbosmart Top Mount Intercooler (TMIC) kit – includes intercooler, silicone hose bends, T-bolt clamps, and mounting hardware
  • New OEM or aftermarket intercooler gaskets (often included with the kit; check before ordering)
  • Engine coolant (Subaru Super Coolant or equivalent) – only needed if you disconnect coolant lines for the throttle body or bypass valve
  • Dielectric grease (for electrical connections)
  • RTV silicone (optional for extra sealing on gaskets)

Safety and Preparation

  • Park the car on level ground and engage the parking brake.
  • Allow the engine to cool completely – at least two hours after last drive. Coolant and turbo components hold heat.
  • Disconnect the negative battery terminal to prevent accidental shorts or airbag deployment.
  • Work in a well-ventilated area, especially if the engine has been running recently.
  • Have a fire extinguisher nearby rated for automotive use.

Step 1: Remove the Engine Cover and Sound Deadening

Start by taking off the plastic engine cover. Use a 10mm socket to remove the four bolts that hold it to the valve covers. Lift the cover straight up; it may have a rubber grommet on the back side. Set it aside. Next, remove any sound-deadening foam or plastic trim that blocks access to the intercooler. On some 2018 models there is a small shroud above the intercooler. Unclip or unscrew it carefully.

Step 2: Disconnect the Battery

Using a 10mm wrench or socket, loosen the nut on the negative (black) terminal. Slide the terminal off the battery post and tuck it away from the battery so it doesn't accidentally touch. This step prevents electrical issues when removing sensors or electronics near the intercooler area.

Step 3: Remove the Stock Intercooler

Now for the main disassembly. Work slowly and label any hoses or clips if needed. Most of the factory hoses are held with spring clamps that can be difficult to remove without the right technique.

3a. Disconnect the Inlet and Outlet Hoses

Locate the two large hoses attached to the stock intercooler: one from the turbocharger compressor outlet and one to the throttle body. Use a flathead screwdriver to pry the spring clamps away from the intercooler nipples. Slide the clamps down the hose. Gently twist and pull the hoses free. If they are stuck, use a bit of penetrating oil around the rubber and let it sit for five minutes.

3b. Disconnect the Bypass Valve Hose

The factory bypass valve (BPV) is mounted to the intercooler. A small vacuum line runs from the BPV to the intake manifold. Pull this line off carefully; it is plastic and can break. If it feels brittle, consider replacing it with a silicone vacuum line.

3c. Remove the Two Bolts Holding the Intercooler

The intercooler is mounted to the engine bay with two 12mm bolts on the top brackets. Use a socket and ratchet extension to reach them. The bolts may be tight from heat cycling. Support the intercooler with your free hand while removing the last bolt. Once both bolts are out, lift the intercooler straight upward. It may need a slight wiggle to clear the engine. Set the stock intercooler aside on a clean surface.

3d. Remove the BPV and Any Brackets

You can reuse the factory BPV or upgrade it later. To transfer it to the new Turbosmart intercooler, undo the two 10mm bolts holding the BPV to the stock intercooler. Pull the BPV off its gasket. Clean the gasket surface and check the rubber seal. If the gasket is torn or compressed, order a new one before reinstalling.

Step 4: Prepare the Turbosmart Intercooler

Take the Turbosmart intercooler out of the box. Inspect it for shipping damage. Check that all fins are straight; a bent fin can be straightened with a small pick. Confirm that you have the correct silicone hoses and T-bolt clamps. The kit typically includes a cold-side hose (turbo to intercooler) and a hot-side hose (intercooler to throttle body). Some kits also have a hose for the BPV.

Pro tip: Before installation, lightly sand the inside edges of the hose openings where they contact the intercooler and throttle body nipples. This removes any molding flash and helps the silicone seal better. Wipe the surfaces clean with alcohol.

Step 5: Install the BPV on the New Intercooler

Attach the stock BPV to the Turbosmart intercooler using the original bolts or the supplied hardware. Tighten to 6-8 ft-lb. Apply a thin film of RTV silicone on the gasket if you want extra insurance against vacuum leaks. For boosted applications, even a small leak at the BPV can cause rough idle or poor performance.

Step 6: Mount the Turbosmart Intercooler

This step is a straightforward reverse of removal, but the new intercooler is taller and wider. You may need to pivot it slightly to get it past the radiator fan shroud and the intake pipe. Work from the driver's side.

6a. Position the Intercooler

Lower the Turbosmart intercooler into the engine bay with the mounting brackets facing forward. Align the two bolt holes on the brackets with the factory mounting points on the chassis. The intercooler should sit parallel to the radiator. Do not force it; if something is binding, check that no hoses or wiring is caught underneath.

6b. Secure the Intercooler with Bolts

Insert the two 12mm bolts (supplied or reuse factory if the threads match) and hand-tighten them. Use a torque wrench set to 18-20 ft-lb. Do not overtighten – the aluminum brackets can strip.

Step 7: Connect the Intercooler Hoses

Now you will install the silicone hoses that come with the Turbosmart kit. These are thicker than stock and provide better sealing with T-bolt clamps.

7a. Turbo Outlet to Intercooler Inlet

Slide one T-bolt clamp onto the short silicone hose. Attach the hose to the intercooler inlet (driver’s side port). Push it on until it bottoms out against the bead. Tighten the clamp to 40-50 in-lb (about 3-4 ft-lb). Then attach the other end of the hose to the turbo compressor outlet. Use a second clamp. Make sure the hose does not contact the fan shroud or drive belt.

7b. Intercooler Outlet to Throttle Body

This hose is typically longer and may have an angled end. Slide the hose onto the intercooler outlet (passenger side port) and clamp it. Then route the other end to the throttle body. The throttle body neck is a flat flange with two bolt holes; you will use a factory-style clamp or the supplied T-bolt. Tighten both clamps evenly.

7c. BPV Vacuum Line

Reconnect the small vacuum line from the intake manifold to the BPV. If the factory line is too short or feels brittle, replace it with a 1/4-inch silicone vacuum hose. Use a zip tie to secure it if needed.

Step 8: Reconnect the Battery and Perform Initial Checks

After double-checking all hose clamps and electrical connectors, reconnect the negative battery terminal. Tighten securely. Turn the key to the ON position but do not start the engine yet. Listen for any electronic hissing or clicking. Press the gas pedal to the floor and release to cycle the throttle body. This ensures the ECU re-learns the idle position.

Step 9: Leak Check and Test Drive

9a. Idle and Visual Inspection

Start the engine and let it idle for two minutes. Look and listen for air leaks around every hose connection. A hissing sound indicates a leak. If you have a smoke machine, this is the time to use it. If you do not have one, spray a small amount of soapy water (not too much) around the hose ends. Bubbles mean a leak. Tighten the clamp slightly until it stops.

9b. Check Coolant Level

If you disconnected any coolant lines (some kits require removing a coolant reservoir bracket), check the coolant level. Top up as needed with Subaru Super Coolant or the correct mixture. Run the engine with the radiator cap off to burp any air pockets. Put the cap back on once the thermostat opens and the coolant flow is steady.

9c. Road Test

Take the car for a gentle drive first. Accelerate part-throttle and let the engine reach operating temperature. Then perform a few full-throttle runs in third gear from 2500 to 5500 RPM. Pay attention to boost pressure – if boost seems low or you hear a loud whistle, shut down and inspect for leaks. The Turbosmart intercooler will slightly increase volume, so boost may spike a bit differently. A tuned car should be fine; stock ECU can adapt within limits.

Step 10: Reinstall Engine Cover (Optional)

You can put the engine cover back on if you prefer the stock appearance. The cover may not fit perfectly because the Turbosmart intercooler is taller. You may need to trim the underside of the cover with a utility knife to clear the intercooler core. If you do not want to modify it, simply leave it off – many enthusiasts do this for better airflow and easier maintenance.

Additional Considerations for Tuning and Performance

Installing a larger TMIC changes the pressure drop across the charge air system. While the stock ECU can compensate with its Mass Airflow (MAF) sensor, you will get the most benefit from a custom tune or an off-the-shelf map from an accessport. The Turbosmart intercooler reduces intake temperatures by up to 30°F on the dyno, allowing the engine to run more aggressive ignition timing without knock.

If you plan to increase boost beyond 20 psi, consider upgrading the bypass valve to a more robust unit. The factory BPV can leak under high boost on a tuned car. A Turbosmart Kompact BPV is a direct upgrade.

Maintenance Tips

  • Inspect the intercooler fins every 5,000 miles for dirt or bugs. Clean with a soft brush or low-pressure water.
  • Check T-bolt clamps for tightness after the first week of driving – heat cycles can loosen them.
  • If you track your car, consider a CO2 sprayer or water-methanol injection for additional cooling.

External Resources

For more technical information and community support, check out these links:

Conclusion

Swapping the factory intercooler for a Turbosmart top mount unit is a weekend project that pays off in lower intake temps and more consistent power. By following this step-by-step guide, you can complete the installation with confidence. The key takeaways: work carefully with the hoses, torque the mounting bolts properly, and always leak-test before your first hard drive. With the Turbosmart TMIC installed, your 2018 WRX is ready to handle more boost and hotter conditions without pulling timing. Enjoy the sharper throttle response and the satisfaction of a job well done.