Why Upgrade to a Forge Motorsport Air to Water Intercooler?

For Subaru WRX owners chasing consistent power, the factory top-mount intercooler often becomes a bottleneck once boost levels or ambient temperatures rise. Heat soak kills performance, and a traditional air-to-air setup has limits in tight engine bays. The Forge Motorsport Air to Water Intercooler solves this by using water as the heat exchange medium, delivering denser intake air and more reliable horsepower. This complete guide walks you through the installation process, from bumper removal to leak checking, so you can get back on the road with confidence.

Unlike a standard top-mount intercooler that relies solely on airflow, an air-to-water system circulates coolant through a dedicated heat exchanger. This design keeps charge air temperatures stable even during stop-and-go traffic or aggressive driving. Forge Motorsport has engineered their kit specifically for the Subaru WRX platform, meaning bolt-on fitment and proven gains. Whether you are a seasoned DIY mechanic or a first-time installer, the following steps will help you complete the job safely and correctly.

What You Get in the Forge Motorsport Kit

Before you start, open the box and verify that all components are present. The Forge kit typically includes the intercooler core, water pump, heat exchanger, silicone hoses, stainless steel clamps, mounting brackets, and a detailed instruction manual. Some kits may also include pre-filled coolant or a bleed kit. Familiarize yourself with each part before lifting a wrench. Missing a bracket or hose can halt your installation midway, so take five minutes for an inventory check.

Tools and Materials You Will Need

Having the right tools on hand makes the difference between a smooth install and a frustrating afternoon. Gather the following items before you begin:

  • Socket set with metric sockets (8mm, 10mm, 12mm, 14mm are most common)
  • Torque wrench (ft-lb and in-lb ranges)
  • Flathead and Phillips screwdrivers
  • Trim removal tools (plastic pry bars for bumper clips)
  • Pliers (standard and hose clamp pliers)
  • Coolant – a 50/50 mix of distilled water and ethylene glycol based coolant
  • Clean rags for spills and surface prep
  • Safety glasses and gloves
  • Jack and jack stands (optional but recommended for bumper clearance)

If your WRX has fog lights or parking sensors, you may also need a small flathead to release electrical connectors. A panel clip tool can save you from breaking plastic fasteners that are brittle with age.

Preparation and Safety

Park your Subaru WRX on a level surface and allow the engine to cool completely. Working on a hot engine increases the risk of burns and makes hose removal more difficult. Disconnect the negative battery terminal to prevent accidental short circuits or fan engagement while you are near the front of the vehicle. If you have a cold air intake or aftermarket induction piping, note their routing so you can work around them without damaging any components.

Work in a well-ventilated area, preferably a garage with good lighting. Having a second set of hands is helpful when aligning the intercooler core and manipulating hoses. Plan for a full afternoon of work — experienced installers can finish in two to three hours, but first-time installation may take four to five hours with careful double-checking.

Step 1: Remove the Front Bumper

Accessing the intercooler requires removing the front bumper cover. This step is straightforward but requires patience with fasteners. Start by opening the hood and removing the plastic push pins along the top edge of the bumper where it meets the grille. Use a trim removal tool to pop these clips without breaking them.

Next, locate the bolts securing the bumper to the fender liners on both sides. There are typically two or three bolts per side using a 10mm socket. Remove the screws along the bottom edge of the bumper that attach it to the under-tray. Some models also have a central bolt near the radiator support. Once all fasteners are out, carefully pull the bumper cover forward, releasing any remaining clips.

If your WRX is equipped with fog lights, unplug the electrical connectors before fully removing the bumper. The same applies to parking sensors or headlight washers. Lay the bumper cover on a soft surface to avoid scratching the paint. With the bumper removed, you now have clear access to the stock intercooler, radiator, and front structure.

Step 2: Drain the Coolant and Remove the Stock Intercooler

The factory top-mount intercooler sits above the engine, but to access its mounting points, you will work primarily from the front. Locate the two coolant hoses connected to the stock intercooler's water circulation system. Place a drain pan underneath and loosen the hose clamps. Be prepared for coolant spillage — have rags handy to catch drips.

Once the hoses are disconnected, remove the mounting bolts that secure the stock intercooler to its bracket. These are typically four bolts using a 12mm socket. Carefully lift the intercooler out, watching for any attached hoses or brackets you may have missed. Set the factory unit aside. This is a good time to inspect the area for debris, oil residue, or damaged fittings that could affect the new installation.

Step 3: Prepare the Mounting Area and Install Brackets

The Forge intercooler uses a dedicated mounting system that bolts directly to existing chassis points. Before you install the core, test-fit the brackets that came with your kit. Forge typically includes a set of laser-cut steel brackets that replace or reinforce the factory mounting points. Attach these brackets using the supplied hardware and torque to the manufacturer's specification — usually around 18-22 ft-lb for chassis bolts.

Clean the mounting surfaces with a rag to remove any dirt or grease. A clean interface ensures the intercooler sits flat and does not vibrate loose over time. If your kit includes foam pads or rubber isolators, install them now. These prevent metal-to-metal contact and reduce noise transmission into the cabin.

Step 4: Install the Forge Motorsport Intercooler Core

With the brackets in place, position the Forge intercooler core into the engine bay. The core should drop into position with minimal force — if it does not fit, double-check your bracket orientation. Align the mounting tabs on the core with the brackets and insert the bolts hand-tight. Once all bolts are started, torque them gradually in a crisscross pattern to ensure even pressure.

The Forge intercooler is designed to sit lower and more forward than the factory unit, which improves airflow through the core. Confirm that the intercooler is level and does not contact the radiator, fan shroud, or hood latch mechanism. A misaligned core can cause vibration or interfere with other components. Spin the engine fan by hand to verify clearance if necessary.

Step 5: Connect the Boost Hoses and Piping

The Forge kit includes silicone hoses that connect the turbocharger outlet to the intercooler inlet and the intercooler outlet to the throttle body. These hoses are reinforced to handle high boost pressures without collapsing. Apply a thin film of silicone lubricant or soapy water to the hose ends to ease installation onto the metal fittings.

Slide the hose onto the turbo outlet first, then route it to the intercooler inlet. Secure each connection with the supplied T-bolt or worm-gear clamps. Do not fully tighten until all hoses are aligned, as you may need to rotate them slightly to avoid kinks. Once the routing is correct, tighten the clamps to approximately 5-6 Nm (45-55 in-lb) — overtightening can damage silicone hoses or strip the clamp threads.

For the outlet side, connect the hose from the intercooler to the throttle body. Ensure the hose does not contact sharp edges or hot engine components. If your kit includes a blow-off valve or bypass valve adapter, install it now according to the supplied diagram. Torque all clamps evenly and check that each connection feels snug.

Step 6: Set Up the Water Circulation System

The air-to-water intercooler relies on a dedicated water system to remove heat from the charge air. This system consists of a water pump, heat exchanger (secondary radiator), reservoir, and hoses. Mount the heat exchanger in front of the main radiator or in the lower bumper opening, depending on the kit design. Use the provided brackets and ensure the heat exchanger is oriented with the inlet and outlet ports accessible.

Mount the water pump near the heat exchanger or on a chassis rail. Secure it with rubber isolators to reduce noise. Route the hoses from the intercooler to the pump, then to the heat exchanger, and finally to the reservoir. A typical flow direction is: intercooler outlet → pump inlet → pump outlet → heat exchanger → reservoir → intercooler inlet. Follow Forge's specific diagram as some kits vary the order.

Fill the system with a 50/50 mix of distilled water and coolant. Using distilled water prevents mineral deposits that can clog the heat exchanger over time. Slowly pour coolant into the reservoir while monitoring for leaks at every connection. Air pockets in the system can cause the pump to cavitate, so bleed the system by loosening the highest hose clamp slightly until coolant seeps out, then retighten. Some installers use a dedicated coolant bleeder funnel for a faster process.

Step 7: Reinstall the Front Bumper and Under-Tray

Before reinstalling the bumper, inspect all connections one more time. Check that hoses are not pinched, clamps are tight, and the intercooler is secure. Reconnect any electrical connectors for fog lights, parking sensors, or ambient lights that were disconnected earlier. Tuck any wiring loom away from moving parts and hot surfaces.

Align the bumper cover with the vehicle body and press it into place. Reinstall the push pins along the top edge, then the side bolts, and finally the screws along the bottom edge. If any clips broke during removal, replace them now to avoid rattles later. Reconnect the battery terminal and start the engine to verify that the cooling fans and lights function correctly.

If you removed the under-tray, reinstall it using the original hardware. The under-tray protects the intercooler and heat exchanger from road debris and helps channel airflow. Do not drive without it, as debris can damage the exposed components.

Step 8: Check for Leaks and Test Drive

With the engine running, inspect every hose connection, the water pump, and the heat exchanger for drips. Use a flashlight to check hard-to-see areas. Let the engine idle until the cooling fan cycles on — this indicates that the main cooling system has reached operating temperature and the water pump is circulating coolant through the intercooler system.

If you have access to a boost leak tester, pressurize the intake system to 10-15 psi and listen for hissing sounds. This step is optional but highly recommended to catch any loose clamps before the vehicle is under load. Without a leak tester, take the car on a short test drive at low boost and monitor coolant temperature and boost response. Listen for unusual noises from the water pump, which could indicate air in the system or a mounting issue.

After the first drive, park the car and let it cool. Recheck the coolant level and top up if necessary. Air pockets often purge during the first few heat cycles, so adding coolant after the initial test drive is normal. Inspect the hose clamps again — some may require a slight retightening after the hoses have seated from thermal expansion.

Performance Gains and Tuning Considerations

With the Forge air-to-water intercooler installed, your WRX will experience lower intake air temperatures, reduced knock counts, and more consistent power delivery. The water-to-air design excels in situations where airflow to the intercooler is limited, such as traffic, autocross, or street driving. Expect intake air temperatures to drop by 30-50°F compared to the factory setup under sustained boost.

If you have an engine management system or access to a tuning tool, consider revisiting your calibration. A cooler, denser charge allows more timing advance and potentially higher boost levels safely. Consult with a qualified tuner who understands Subaru's MAF-based fueling system. Many WRX owners pair an air-to-water intercooler with a larger turbocharger and fuel system upgrades, but even on a stock turbo, the gains are noticeable.

For more technical details on intercooler efficiency and water-to-air system design, refer to Forge Motorsport's official documentation and NASIOC technical articles where veteran WRX owners share their experiences.

Maintenance Tips for Long-Term Reliability

An air-to-water intercooler requires periodic maintenance to perform at its best. Check the coolant level in the reservoir every oil change and top up with the same 50/50 mix. Over time, coolant can become contaminated with debris or lose its corrosion inhibitors. Flush the system every two years or 30,000 miles, whichever comes first.

Inspect the silicone hoses for cracks, abrasion, or swelling, especially near the clamps. Silicone degrades faster when exposed to oil mist or high under-hood temperatures. Replace any hose that shows signs of wear before it fails under boost. The water pump should be checked for leaks or unusual operation; most pumps last 50,000 miles under normal use, but off-road or track use may shorten that interval.

Keep the heat exchanger fins clean by gently washing them with a low-pressure hose. Avoid using a pressure washer directly on the fins, as they can bend and reduce airflow. A clean heat exchanger sheds heat more efficiently, keeping your intercooler system performing optimally.

Final Thoughts

The Forge Motorsport Air to Water Intercooler is a well-engineered upgrade that transforms how your Subaru WRX handles heat. With the detailed steps above, you can complete the installation at home and immediately feel the difference in throttle response and consistency. The investment pays off every time you accelerate out of a corner or merge onto the highway in warm weather.

Whether you are building a track-focused WRX or simply want more reliable daily performance, the air-to-water setup from Forge delivers measurable results. Take your time during installation, double-check every connection, and maintain the system properly. Your engine will reward you with smoother power and greater resistance to heat soak. For ongoing community support, visit Subaru enthusiast forums where owners share their tuning experiences and installation tips.