Installing the FA24 Engine Performance Upgrade: Cost Breakdown and Step-by-step Process

The Subaru FA24 engine, a 2.4-liter flat-four found in models like the 2022+ WRX, BRZ, and Ascent, is a stout powerplant from the factory. But with the right upgrades, it can deliver significantly more horsepower and torque while maintaining daily-driver reliability. This guide provides a comprehensive cost breakdown and a detailed step-by-step process for installing a performance upgrade on the FA24 engine. Whether you’re aiming for a stage 1 tune or a full bolt-on build, knowing what to expect in terms of parts, labor, and procedure is critical to a successful build.

Understanding the FA24 Engine and Its Upgrade Potential

The FA24 is a direct-injected, twin-scroll turbocharged engine that replaced the earlier FA20 in many Subaru models. Its larger displacement and stronger bottom end make it more tolerant of increased boost and airflow. Stock, the FA24 in the WRX produces around 271 horsepower and 258 lb-ft of torque. With a simple ECU tune, those numbers can jump to 300+ horsepower safely. With bolt-on parts and a proper tune, 350–400 horsepower is achievable on pump gas. Understanding the engine’s architecture—closed-deck block, forged connecting rods, and high-flow cylinder heads—helps you choose upgrades that work in harmony.

Performance upgrades generally fall into three categories: software (tuning), intake/exhaust modifications, and forced induction or fueling enhancements. This guide focuses on a balanced “stage 2” package: an aftermarket intake, a catted downpipe, an intercooler upgrade, and a custom tune. We’ll also outline options for more aggressive builds.

Cost Breakdown of the FA24 Performance Upgrade

Below is a realistic cost breakdown for a typical stage 2 FA24 upgrade. Prices are in USD and may vary by brand, retailer, and region.

  • Performance Parts: $1,800 – $3,500
    • Cold-air intake: $300 – $600
    • Catted downpipe (j-pipe for WRX): $400 – $800
    • Front-mount or upgraded top-mount intercooler: $500 – $1,200
    • Charge pipe kit: $150 – $300
    • Exhaust system (cat-back optional): $400 – $1,000
    • AccessPort or open-source tuning hardware: $400 – $700
  • Labor Costs (if not DIY): $600 – $1,200
    • Intake and intercooler install: 2–3 hours
    • Downpipe install: 2–4 hours (may need a lift)
    • Exhaust system install: 1–2 hours
    • Initial tune (dyno or road tune): $300 – $500 extra if not included
  • Tuning Software / Professional Tune: $300 – $700
    • AccessPort (used by most platforms): $395 – $650
    • Remote e-tune: $250 – $400
    • Dyno tune: $500 – $800
  • Miscellaneous Supplies: $100 – $300
    • Gaskets (turbo-to-downpipe, exhaust): $30 – $70
    • Hardware (bolts, nuts, washers): $20 – $40
    • Coolant (if draining): $20 – $30
    • Shop towels, thread locker, anti-seize: $20 – $40
    • Optional: boost controller, wideband O2 sensor: $100 – $200

Total estimate: $2,800 – $5,700 depending on parts choice, labor vs DIY, and tuning method. For a simple off-the-shelf (OTS) tune with just an intake and exhaust, costs are on the lower end. For a fully optimized setup with a professional dyno tune, expect the higher end.

Step-by-Step Installation Process

This process assumes you have basic mechanical skills, a complete tool set, and a safe workspace. Always refer to the specific instructions from your parts manufacturer. We’ll outline a typical order for a stage 2 FA24 upgrade (intake, intercooler, downpipe, and tune).

Step 1: Gather Tools and Parts

Before starting, verify all parts are present and correct. Tools needed include:

  • Socket set (metric: 8mm, 10mm, 12mm, 14mm, 17mm, 19mm)
  • Combination wrenches
  • Torque wrench (ft-lb and in-lb)
  • Screwdrivers (flathead and Phillips)
  • Pry bar or trim removal tools
  • Jack stands and floor jack (or lift)
  • Oil catch pan (for coolant or oil if needed)
  • Safety glasses and gloves

Step 2: Disconnect the Battery

Safety first. Disconnect the negative battery terminal. Let the car sit for 10 minutes to allow any capacitive discharge. This prevents accidental shorts and resets the ECU for tuning later.

Step 3: Remove the Engine Cover and Air Intake Ducting

The plastic engine cover is held by several bolts (usually 10mm). Remove it. Also unclip the factory air intake duct from the airbox to the turbo inlet. You may need to remove the snorkel from the front grille area. Keep all fasteners organized.

Step 4: Install the Aftermarket Intake System

Most FA24 intakes replace the entire stock airbox and intake tube. Follow these general steps:

  • Unbolt the factory airbox and remove the stock filter.
  • Disconnect the mass air flow (MAF) sensor connector and remove the sensor from the stock housing. Carefully set it aside.
  • Install the MAF sensor into the new intake tube (use the supplied grommet).
  • Mount the new intake filter and heat shield.
  • Secure all hose clamps. Ensure no vacuum lines are pinched.
  • Reconnect the MAF sensor plug.

Tip: Some intakes require a new turbo inlet hose. If your kit includes one, now is the time to swap it. This can be tricky due to tight clearance by the turbo—use a small amount of silicone lubricant.

Step 5: Upgrade the Intercooler System

The FA24’s top-mount intercooler is adequate for stock levels but becomes a restriction with increased boost. Replacing it with a larger top-mount or a front-mount intercooler (FMIC) will reduce intake air temperatures. For this guide, we’ll cover a direct-fit top-mount upgrade.

  • Remove the charge pipes: loosen clamps at the turbo outlet and throttle body. For a top-mount, you’ll typically remove the two short pipes.
  • Unbolt the stock intercooler (usually 4–6 bolts). Lift it out. Be careful—it may be heavy.
  • Install the new intercooler into the same location. Use new gaskets or o-rings if provided.
  • Attach the new charge pipes (if included) or re-use the stock ones if they match. Tighten all clamps to recommended torque (usually 50–70 in-lb).
  • If installing a FMIC, you’ll need to remove the front bumper cover and mount the core behind the grille. This is more involved—allow 4–6 hours.

Step 6: Replace the Downpipe (J-pipe) and Exhaust System

This is often the highest-impact exhaust modification. On the FA24 WRX, the downpipe is often called a “pipe” but functionally it’s the same. A high-flow catted downpipe reduces backpressure while still keeping emissions reasonable.

  • Raise the vehicle and support on jack stands. Ensure the exhaust is cold.
  • Remove the heat shields from the turbo and downpipe area.
  • Unbolt the downpipe from the turbo (typically 4–6 studs with nuts). The hardware is high-temp—apply penetrating oil beforehand.
  • Disconnect the O2 sensors (wideband and/or narrowband). Be careful not to damage the wiring.
  • Remove the downpipe from the mid-pipe. You may need to separate the exhaust system at the mid-pipe joint.
  • Install the new downpipe. Use new gaskets (turbo-to-downpipe and downpipe-to-mid-pipe). Torque the turbo stud nuts to 35–45 ft-lb.
  • Reinstall O2 sensors into the new downpipe bungs. Apply anti-seize to the threads.
  • If replacing the cat-back exhaust, now is the time. Slide the new cat-back onto the mid-pipe, align hangers, and tighten clamps.
  • Important: Some aftermarket downpipes may trigger a check engine light for catalyst efficiency. A tune will usually disable that code.

Step 7: Inspect and Reconnect All Systems

Double-check every clamp, bolt, and connection. Look for loose vacuum lines or wiring that may rub against hot surfaces. Reinstall the engine cover (if it fits with the new intake) or leave it off for better airflow.

  • Reconnect the battery.
  • Prime the fuel system by turning the ignition to the “ON” position for a few seconds without starting. Do this three times.
  • Check for any coolant or oil leaks if you disturbed those systems.

Step 8: Tune the Engine

Do NOT drive the car before loading a proper tune. Running the FA24 with increased airflow and no calibration can cause knock, high exhaust gas temperatures, and engine damage.

  • If using an AccessPort, connect it to the OBD-II port. Follow the device prompts to marry it to your vehicle and flash the appropriate stage 2 OTS map (or upload a custom tune from your tuner).
  • For an e-tune, perform a data-logging session as instructed by your tuner. Send logs, receive revised maps, repeat until perfect.
  • After flashing, let the engine idle for 5–10 minutes while monitoring coolant temp, oil pressure, and air-fuel ratios. No odd noises? Perform a gentle test drive, avoiding full throttle.
  • Complete a series of pulls (3rd or 4th gear) while logging to verify knock correction and fuel trims.

Pro tip: Consider a professional dyno tune for maximum power and safety. A tuner can eke out an extra 20–30 horsepower over OTS maps and tailor the calibration to your specific fuel quality and parts.

Post-Installation Checks and Maintenance

After the tune is finalized, perform a full inspection after 100 miles:

  • Retorque all exhaust bolts and intercooler clamps.
  • Check for boost leaks (listen for hissing, or use a boost leak tester).
  • Change the engine oil and filter—the first drive can dislodge debris from the build.
  • Reset the ECU again (or use the AccessPort to reset learning) and do a second round of logging.

Ongoing maintenance becomes more important with increased power. Shorten oil change intervals to 3,000–4,000 miles. Use high-quality synthetic oil (5W-30 or 0W-40 depending on climate). Upgrade the spark plugs to one step colder if running high boost (over 20 psi).

Common Mistakes to Avoid

  • Installing parts before the tune is loaded. Always flash the tune first.
  • Over-tightening clamps on silicone hoses—can cause tears. Use a torque wrench set to manufacturer specs.
  • Forgetting to tighten the wastegate actuator rod—leads to overboost and limp mode.
  • Using a generic “stage 2” OTS map with mismatched parts (e.g., an intake that differs from the map’s requirements). Verify compatibility.
  • Neglecting to reset the ECU after the initial install—the car may run poorly until the learning cycle completes.

Should You DIY or Hire a Professional?

If you’re comfortable with basic wrenching and have access to a lift or jack stands, the mechanical portion is DIY-friendly. The most challenging parts are removing the downpipe (rusted nuts are common) and installing the intercooler if clearances are tight. For the tuning, a remote e-tune is a good middle ground: you install everything, then a professional handles the calibration via data logs. If you want a turnkey solution, find a reputable Subaru specialty shop that has experience with the FA24 platform. Look for shops on forums like Subispeed or IWSTI.

Performance Gains to Expect

With a stage 2 setup (intake, intercooler, downpipe, and tune) on 93 octane, typical gains are 80–100 horsepower and 90–110 lb-ft of torque over stock. That puts the FA24 in the 350–370 whp range (depending on dyno). Upgrading the turbo (e.g., to a Garrett GTX or stock location turbore) requires fueling mods and pushes the cost above $6,000 but yields 450+ whp. For daily driving, a stage 2 setup offers the best balance of power and drivability. Refer to resources like Driven Performance for dyno charts and parts kits.

Final Thoughts

Installing an FA24 engine performance upgrade is a rewarding project that transforms the driving experience. By carefully selecting parts, budgeting for labor and tuning, and following a methodical installation process, you can achieve impressive power gains without sacrificing reliability. Always prioritize proper tuning—it’s the single most important part of the upgrade. For further reading, check out forums like SubaruXYZ or the comprehensive guides on Cobb Tuning. With the right approach, your FA24 will deliver a thrilling ride every time you press the throttle.