The FA24 engine has rapidly become a favorite among performance enthusiasts, particularly with its introduction in the Subaru WRX (2022+) and the Ascent. This 2.4-liter turbocharged flat-four offers a robust foundation for power increases, and upgrading the turbocharger is one of the most effective ways to unlock an additional 70+ horsepower. This article provides a deep dive into dyno-proven turbocharger upgrades for the FA24, covering options, supporting modifications, tuning requirements, and real-world results to help you build a reliable and powerful setup.

Understanding the FA24 Engine

The FA24F, as it’s officially designated, is a 2.4-liter (2387 cc) turbocharged boxer engine that replaced the previous 2.0-liter FA20F in several Subaru models. It features a closed-deck block design for increased strength, a twin-scroll turbocharger from the factory, and direct injection. The factory power output ranges from 260 hp (in the Ascent) to 271 hp (in the WRX), but the engine’s architecture supports far more. Key specifications include a 94.0 mm bore and 86.0 mm stroke, with a compression ratio of 10.1:1 in the Ascent and slightly lower 9.9:1 in the WRX to handle boost. The engine’s direct injection helps with knock resistance, but it also limits fueling capacity compared to port injection – a consideration when upgrading turbos.

The FA24’s twin-scroll turbo design provides excellent low-end torque and quick spool, but the factory turbo quickly becomes a bottleneck once you start pushing beyond its efficiency island. Upgrading to a larger or more efficient turbocharger allows you to maintain low-RPM response while vastly increasing top-end power. Many owners have seen gains of 70–120 whp simply by swapping the turbo, adding a tune, and upgrading the fuel system.

Benefits of Turbocharger Upgrades

Moving from the stock turbo to a performance unit delivers several measurable benefits:

  • Massive Horsepower Gains: Dyno-proven results consistently show gains of 70–120 whp depending on the turbo and supporting mods.
  • Improved Torque Curve: Larger turbos can maintain peak torque across a wider RPM range, improving acceleration and drivability.
  • Better Throttle Response: Many aftermarket turbos (especially ball-bearing units) spool nearly as fast as stock while flowing more air.
  • Custom Power Band: Choose between quick-spooling street turbos or high-end race units that emphasize peak horsepower.
  • Enhanced Reliability: Many upgraded turbos include billet wheels and stronger bearings, reducing the risk of failure at elevated boost levels.

Several turbochargers have been extensively tested on the FA24 platform. Below are the most popular options, each with unique characteristics.

Garrett GTX2860R

The GTX2860R is a compact ball-bearing turbo known for its lightning-fast spool and high efficiency. It features a 52mm compressor wheel and a 60mm turbine wheel, capable of supporting up to ~350 hp on the FA24. Many owners pair it with a boost controller to run 20–22 psi, achieving 320–340 whp with proper tuning. Its small frame means excellent drivability, making it ideal for daily drivers who want a significant power increase without sacrificing response. Learn more about Garrett’s GTX2860R Gen II.

Blouch 1.5XTR

Blouch Performance is a well-respected name in Subaru turbo upgrades, and their 1.5XTR is a favorite for FA24 builds. This turbo uses a 6720 billet wheel and a 9.5cm² turbine housing, offering a nice balance between spool and top-end flow. On the dyno, it’s been measured at 340 whp at 22 psi with supporting mods like a front-mount intercooler (FMIC) and a bigger fuel pump. The 1.5XTR retains twin-scroll capability, so you don’t lose the factory’s exhaust manifold benefits. View Blouch’s FA24 upgrade options.

FP Green Turbo

Forced Performance’s FP Green is a classic Subaru upgrade that has been adapted for the FA24. The current version uses a GBP (Garrett-Ball-Bearing) core and a 68mm compressor wheel. It’s larger than the GTX2860R and Blouch 1.5XTR, flowing enough to support 400+ whp. Many FA24 dyno sheets show 330–350 whp at 21 psi with the FP Green, though it spools slightly later than the smaller options. The trade-off is a stronger top-end pull. It’s a great choice for track-day cars where high RPM power matters.

ATP GT2860RS

ATP Turbo’s GT2860RS (often called the “DISCO POTATO”) brings a Garrett GT2860RS cartridge with a custom actuator and housing for the FA24. It produces 310 whp at 19 psi, with a very smooth, linear power curve. This option is conservative but offers exceptional reliability and compatibility with stock location intercoolers. It’s a good entry-level upgrade for those who want realistic 70+ hp gains without major modifications.

Dyno-Proven Results – Detailed Breakdown

We’ve gathered real-world dyno data from multiple FA24 builds to illustrate the potential. All figures are wheel horsepower (whp) on a Mustang or Dynojet dyno, corrected for temperature and barometric pressure.

Turbocharger Peak WHP Boost Level Fuel Type Supporting Mods
Garrett GTX2860R 320 20 psi 93 octane FMIC, intake, catback exhaust
Blouch 1.5XTR 340 22 psi 93 octane + methanol FMIC, TGV deletes, upgraded fuel pump
FP Green 335 21 psi 93 octane FMIC, hard-pipe intake, catless downpipe
ATP GT2860RS 310 19 psi 93 octane Drop-in filter, CVD (cat-back only)

Note that these numbers are based on conservative tunes. With ethanol blends (E30 or E60) and more aggressive tuning, many of these turbos can produce 350–400 whp. For instance, the Blouch 1.5XTR on E60 has been documented at 380 whp at 24 psi. Always confirm dyno results with your tuner and verify that your internals can handle the power.

Supporting Modifications for Turbo Upgrades

Simply swapping the turbo without complementary upgrades will leave performance on the table and may cause reliability issues. Here are the essential supporting modifications:

Fuel System Upgrades

The FA24’s direct injection can handle moderate power increases, but once you exceed 340–350 whp, the HPFP (high-pressure fuel pump) and injectors become limiting. Upgrades include:

  • High-pressure fuel pump: Companies like Nostrum and AEM offer upgraded HPFPs that increase fuel volume.
  • Low-pressure fuel pump: A higher-flow in-tank pump (e.g., Walbro 525) ensures the HPFP has enough supply.
  • Port injection: Many high-power FA24 builds add port injection (from IAG or AEM) to supplement the direct injectors and allow higher ethanol content.

Intercooling

A larger intercooler is critical. The factory top-mount (TMIC) becomes heat-soaked quickly at elevated boost. Options include a front-mount intercooler (FMIC) from companies like Process West, ETS, or Cobb, or a thicker TMIC like the Grimmspeed TMIC. FMICs generally provide better heat rejection on road course or heavy traffic situations.

Exhaust System

A free-flowing downpipe and cat-back exhaust reduce backpressure and help the turbo spool. A catless downpipe will give the biggest gain, but check your local emissions regulations. A 3-inch turbo-back exhaust is common for FA24 builds aimed at 350+ whp.

Intake and Charge Pipes

The stock airbox can restrict airflow on larger turbos. A cold air intake (CAI) from AMS or Cobb, along with hard charge pipes, reduces restriction and improves throttle response. Be sure to use a filter with proper filtration – a dry filter is preferred to avoid oil contamination of the MAF sensor.

Engine Management – Tuning and Tuning Devices

You cannot simply bolt on a bigger turbo and drive away. The FA24’s factory ECU needs recalibration to adjust fuel, timing, boost targets, and MAF scaling. Two primary routes exist:

  • Cobb Accessport: The most common tuning tool for the FA24. Off-the-shelf (OTS) maps are available from Cobb for some turbo upgrades, but custom tuning via a dyno or e-tune is recommended for maximum safety and power.
  • ECU Flash via ECUTek or RomRaider: Many professional tuners use ECUTek for advanced features like flex-fuel tuning and boost-by-gear. RomRaider is an open-source alternative but less supported on newer ECUs.

Installation Considerations

Installing an aftermarket turbo on the FA24 is a moderate-difficulty job. Expect to spend 6–12 hours if working in your garage, or about 4–6 hours at a shop. Key steps include:

  1. Draining coolant and engine oil (the turbo shares oil and water lines).
  2. Removing the factory heat shield, downpipe, and intercooler piping.
  3. Disconnecting the oil feed line, water lines, and wastegate actuator.
  4. Bolt-on the new turbo, using new gaskets and crush washers.
  5. Re-routing intercooler piping if switching to FMIC or top-mount conversions.
  6. Refilling fluids, checking for leaks, then performing a tune.

Some turbos may require a custom oil feed restrictor or different coolant routing – check the manufacturer’s instructions carefully. It’s also wise to upgrade the oil line to an AN-braided line for reliability.

Reliability and Maintenance

Adding 70+ horsepower predictably increases stress on the engine. While the FA24 bottom end is strong, several areas require attention:

  • Rod bearings: Sustained high torque at low RPM can cause spun bearings. Use a proper tune that doesn’t allow boost below 3000 RPM, and consider a high-quality oil like Redline 5W-40.
  • Cooling: Higher boost generates more heat. Upgrading to a larger radiator and an oil cooler is recommended for track use.
  • Timing chain tension: Some owners replace the timing chain tensioner with a heavier-duty unit (from IAG) to prevent chain slap at high HP.
  • PCV system: With increased blow-by, a catch can or AOS (air-oil separator) is highly recommended to keep oil out of the intake tract.

Cost Breakdown

A turbo upgrade is a significant investment. Below is an approximate budget for a complete setup targeting 70–100 whp gain:

  • Turbocharger: $1,200 – $2,500
  • Intercooler: $500 – $1,200 (FMIC) or $600 – $800 (upgraded TMIC)
  • Downpipe (catless): $300 – $600
  • Intake kit: $300 – $500
  • Fuel pump upgrade: $200 – $400
  • Tuning device (Accessport) and tune: $650 – $1,000
  • Labor (if paying shop): $500 – $1,200
  • Total: approximately $3,500 – $7,500 depending on choices

While not cheap, the cost per horsepower is often better than other engine modifications like cams or porting.

Real-World Driving Impressions

Owners who have done turbo upgrades report a transformed driving experience. The stock FA24 feels strong but runs out of steam above 5500 RPM. With a GTX2860R, for example, the car pulls hard from 3000 RPM all the way to redline, and the boost holds steady. The FP Green offers an even more intense top-end rush, ideal for roll-racing or track days. Regardless of choice, the 70+ hp increase is very noticeable – the car feels significantly faster in every gear.

Conclusion

Upgrading the turbocharger on your FA24 engine is one of the most rewarding modifications you can make. With dyno-proven gains of 70–120 whp, the right turbo can transform a mild-mannered daily driver into a legitimate performance machine. Options like the Garrett GTX2860R, Blouch 1.5XTR, FP Green, and ATP GT2860RS each offer unique benefits that suit different driving styles and power goals. To ensure success, invest in supporting modifications, secure a professional tune, and stay on top of maintenance. The FA24 platform has enormous potential – and a turbo upgrade is the key to unlocking it responsibly.