Introduction: Why the FA20 Benefits from a Larger Intercooler

The FA20 engine, found in vehicles like the Subaru BRZ, Toyota GT86, and Scion FR-S, is a 2.0-liter boxer engine known for its high-revving nature and aftermarket tuning potential. While the naturally aspirated version earned a reputation for linear power delivery, the turbocharged FA20 (e.g., in the Subaru Levorg or aftermarket forced-induction builds) suffers from a common limitation: heat soak. The factory intercooler, designed for modest boost levels and daily driving, quickly becomes a bottleneck when power targets rise. Upgrading to a larger, more efficient intercooler is one of the most impactful modifications you can make to unlock consistent performance. This article provides a detailed, data-backed analysis of the performance gains, costs, and installation considerations for fitting a larger intercooler to the FA20.

Understanding Intercooler Function and the FA20’s Stock Limitations

An intercooler is an air-to-air heat exchanger placed between the turbocharger compressor outlet and the engine intake. Its job is to reduce the temperature of the compressed intake charge. According to the ideal gas law, cooling the air increases its density without changing pressure, meaning more oxygen molecules enter the cylinder per cycle. This directly translates to higher power output and reduced risk of detonation (knock).

The stock FA20 intercooler is typically a bar-and-plate or tube-and-fin design sized for 8–10 psi of boost. On a turbocharged FA20 (whether OEM or aftermarket), the factory unit can struggle to keep intake air temperatures (IATs) within a safe range after just a few hard pulls. IATs can spike by 40–60°F (22–33°C) in a single 3rd-gear pull, causing the ECU to pull timing and reduce power. A larger intercooler addresses this by:

  • Increasing core volume – holds more cooling air and allows longer residence time for heat transfer.
  • Improving fin density and internal turbulators – enhances heat exchange efficiency.
  • Reducing pressure drop – larger core and smoother end tanks keep flow velocity in check, minimizing boost loss.

For more on intercooler theory, EngineLabs offers a deep dive into core sizing and pressure drop trade-offs.

Why the FA20 Specifically Demands a Better Intercooler

The FA20’s horizontally opposed (boxer) layout means the engine bay is already tight. The stock intercooler sits between the radiator and the engine in an area with limited airflow at low speeds. When you push the car harder – on a track, during autocross, or on a long mountain road – the factory intercooler quickly becomes heat-soaked because it can’t shed heat fast enough. Many owners report that after three back-to-back full-throttle runs, the car feels noticeably slower. A larger intercooler with a thicker core and better end-tank casting mitigates this, maintaining consistent IATs within 10–15°F of ambient even under sustained load.

Performance Gains: Measurable Benefits on the FA20

The benefits of upgrading the intercooler are not just speculative; they have been documented on dynos and in real-world testing. Here’s what you can expect:

1. Increased Power Output

The most obvious gain is peak horsepower and torque. With a larger intercooler, IATs drop significantly, allowing the ECU to run more aggressive timing. On a stock turbo FA20 running 12–14 psi, a good intercooler can add 10–20 whp at the top end, simply by reducing knock retard. On a modified setup with a larger turbo and higher boost (18–22 psi), the gains can exceed 30–40 whp. For example, a builder on the Subaru technical forums reported a gain of 18 whp and 22 lb-ft of torque after swapping from the stock unit to a 4-inch-thick bar-and-plate intercooler, with no other changes apart from a retune.

2. Improved Engine Efficiency and Consistency

Cooler air also improves volumetric efficiency. The engine burns fuel more completely, which can yield a slight improvement in fuel economy under cruising conditions. More importantly, the power delivery becomes repeatable. On a hot summer day, a car with a factory intercooler might lose 15–20 hp after a single pass. A larger intercooler keeps power levels consistent run after run, making it invaluable for track use or drag racing.

3. Better Performance Under Load (Heat Soak Resistance)

The thermal mass of a larger core means it takes longer for the intercooler to reach saturation temperature. Combined with a larger frontal area and better fin design, the upgraded unit recovers faster between pulls. In stop-and-go traffic or after a standing start, the stock intercooler can heat-soak in under 30 seconds; a larger unit may take two to three times longer, and even then, the absolute IATs will be lower.

4. Enhanced Turbo Response

Lower intake air temperatures also contribute to reduced turbo lag. Cooler, denser air moves more readily through the intake tract and into the cylinders. While the effect is small (maybe 100–200 rpm improvement in spool on smaller turbos), every bit helps when building a responsive FA20.

Cost Analysis: Breaking Down the Investment

Upgrading an intercooler isn’t just the price of the core. You need to account for every component and related mod. Below is a detailed cost breakdown based on current market pricing (as of 2025).

Intercooler Core and Kit

  • Budget / Universal cores: $150–$300 – these are generic bar-and-plate cores that require custom piping fabrication. They can work but often have fitment challenges and mediocre end tanks.
  • Mid-range direct-fit kits (e.g., Mishimoto, GReddy, Process West): $400–$800 – these include polished aluminum piping, silicone couplers, T-bolt clamps, and a mounting bracket. Direct-fit design reduces installation time.
  • High-end / race-oriented kits (e.g., Perrin, Turbosmart, custom fabricated): $800–$1,500 – these use thicker cores (4–5 inches), cast end tanks with smoother transitions, and optimized flow paths. Often include a blow-off valve adapter.

Mishimoto’s intercooler guide provides a good overview of core design differences. Expect to spend $500–$1,200 for a quality kit that fits the FA20 without extensive modification.

Installation Costs

  • DIY: If you have a jack, stands, basic hand tools, and about 4–6 hours, you can do it yourself. Budget $0 for labor, but consider buying a torque wrench and a metal pick set (~$40).
  • Professional installation (shop rate $100–$150/hr): Most shops charge 3–5 hours for intercooler replacement on an FA20, totaling $300–$750. If you also need custom piping, expect more time.
  • Additional modifications: You may need to relocate the washer fluid reservoir or trim the bumper crash bar, especially on thicker cores. Professional fabrication adds $100–$300.

Additional Parts and Supporting Mods

  • Piping and couplers: Many kits include them. If not, 2.5" or 3" aluminum piping costs $50–$150 per bend. Silicone couplers (~$5 each) and T-bolt clamps (~$3 each) add up.
  • Blow-off valve (BOV): Often the stock BOV can be reused, but many upgrade to a vent-to-atmosphere unit. A quality BOV (e.g., Turbosmart, HKS) adds $150–$300.
  • Tuning: After installing a larger intercooler, you must retune. The increased flow rate and lower IATs mean the engine will lean out if the ECU is not adjusted. A custom dyno tune costs $400–$800. A remote e-tune using a Cobb AccessPort or EcuTek cable runs $250–$500. Cobb Tuning’s FA20 guide is a great starting point for understanding the tuning process.

Total estimated cost (all-in, including tune): $900–$2,300, depending on parts and labor choices.

Installation Process: Step-by-Step for the FA20

Installing a larger intercooler on an FA20 is a moderately difficult job, suitable for an intermediate DIYer. Always work on a cold engine and disconnect the negative battery terminal. The following steps assume a direct-fit kit (e.g., Mishimoto or Process West).

Tools Required

  • Socket set (metric, 8mm–17mm)
  • Torx bits (T25, T30)
  • Flathead and Phillips screwdrivers
  • Trim removal tools
  • Jack and jack stands (or ramps)
  • Pliers (for hose clamps)
  • Torque wrench (for final tightening)

Step 1: Preparation

Park the car on level ground, disconnect the battery, and remove the key. Remove the front bumper cover: undo the screws/bolts along the top edge (under the hood), inside the wheel wells (plastic push clips), and along the bottom tray. Gently pull the bumper forward and set it aside. Remove the plastic crash bar cover (if present).

Step 2: Remove the Stock Intercooler

Disconnect the charge air piping from the turbo outlet to the intercooler. On the FA20, the stock piping uses spring clamps – slide them back with pliers and pull the hoses off. Unbolt the intercooler from its mounting brackets (usually 10mm bolts). Carefully lift the stock intercooler out from the top or bottom, depending on clearance. You may need to loosen the radiator fan shroud to create space.

Step 3: Prepare the New Intercooler

Compare the new unit with the stock one. Check that all mounting brackets line up. Many aftermarket intercoolers require you to transfer or install new brackets – follow the manufacturer’s instructions. Fit the silicone couplers onto the intercooler inlets/outlets and lightly tighten the clamps so they stay in place but can still rotate.

Step 4: Install the New Intercooler

Position the new intercooler in the engine bay. For most FA20 applications, the intercooler sits between the radiator and the engine. Some kits move it slightly forward to use the space behind the grille. Bolt it into place using the provided hardware. Do not fully torque yet – leave mounting bolts snug to allow adjustment. Connect the charge pipes, ensuring they are fully seated. Use T-bolt clamps and tighten to the specified torque (typically 20–25 in-lbs for silicone couplers).

Step 5: Reassemble and Check Fitments

Reattach the bumper crash bar (if removed) and then the bumper cover. Check that no hoses or wiring are pinched. Reconnect the battery. Start the engine and let it idle for 2 minutes to build boost pressure – listen for any hissing (indicating a leak). If you have a boost leak tester (or a spray bottle with soapy water), check all connections. Shut down the engine and re-tighten any loose clamps.

Step 6: Tuning

This step is mandatory. Contact a tuner who specializes in FA20 engines. They will adjust fuel, timing, and boost control maps to match the new intercooler’s flow characteristics and lower IATs. A proper tune not only maximizes power but also prevents knock. Drive the car for 100–200 miles before the final dyno session to allow the ECU to adapt to the new hardware.

Potential Challenges and How to Overcome Them

Even with a direct-fit kit, you may encounter obstacles. Here are common issues and their solutions:

Fitment Issues

Larger intercoolers (especially 4+ inch thick cores) can contact the radiator hose, power steering lines, or the AC condenser. Some hoods require a slight trim on the inner liner. Solution: Purchase a kit specifically designed for the FA20 chassis. Avoid universal cores unless you are skilled with fabrication. If trimming is necessary, use a Dremel or fine-tooth saw, and deburr any sharp edges.

Increased Weight

A larger core can add 4–8 pounds (1.8–3.6 kg) up front, which slightly affects steering feel and weight distribution. Solution: This weight is negligible for most street and track cars. If you are competitive in time attack, consider a lighter all-aluminum intercooler (some use aluminum core with plastic end tanks) but be aware that plastic end tanks are less durable under high boost.

Cooling System Compatibility

If the intercooler overlaps the radiator, airflow can be reduced, potentially causing engine coolant temps to rise. Solution: Ensure the intercooler has a high-density fin design that doesn’t block too much of the radiator. Some kits include a lower temperature thermostat or recommend a hood scoop upgrade. Monitor coolant temps after installation; if they increase by more than 5°F during heavy driving, consider a larger radiator or oil cooler.

Pressure Drop Considerations

A very large core can cause too much pressure drop, hurting spool and low-end torque. Solution: Look for an intercooler with a pressure drop of <1 psi at your target boost level. Quality manufacturers publish this data. For the FA20, a core volume of 500–700 cubic inches is a good balance for setups up to 400 whp. Beyond that, a stepped core or dual-pass design helps.

Long-Term Durability and Maintenance

Once installed, a larger intercooler requires minimal maintenance. Periodic inspections for rocks or debris damage to the front grille area are wise – consider installing a mesh grille or intercooler guard. Clean the fins gently with a fin comb and low-pressure water to remove bugs and oil residue. Inspect silicone couplers annually for cracking. Most aftermarket intercoolers come with a limited lifetime warranty (check the brand’s policy).

Conclusion: Is a Larger Intercooler Worth It for Your FA20?

For any FA20 running more than stock boost – whether from a factory turbo, aftermarket turbo kit, or supercharger – upgrading the intercooler is among the highest-value modifications. The performance gains in consistent power, reduced knock risk, and improved turbo response are tangible, and the cost, while not trivial, is reasonable compared to internal engine work. Even on a mildly tuned car (around 250–300 whp), a larger intercooler provides headroom for future upgrades and protects the engine during hot weather driving.

If you are budget-conscious, consider a high-quality mid-range kit and do the installation yourself. If you are building a track car, invest in a top-tier core with cast end tanks and plan for a professional tune. Either way, the larger intercooler will pay dividends in driving enjoyment and engine longevity. Proper planning, careful installation, and a professional tune will ensure the modification is a success.

For further reading on intercooler selection and FA20 specific builds, refer to FT86 SpeedFactory’s intercooler install guide and Subaru’s official FA20 performance parts page.