Introduction: Unlocking the VA WRX's True Potential

The Subaru VA WRX (2015–2021) has earned a loyal following thanks to its capable FA20 turbocharged engine and well-balanced chassis. While the stock turbo system delivers respectable power, many owners quickly find themselves wanting more. The 350-wheel-horsepower (whp) mark is a popular and realistic target—a sweet spot that transforms the daily driver into a genuine performance machine without requiring a built engine or enormous budgets. Reaching that number, however, demands more than just bolting on a larger turbo. A thoughtful combination of a properly matched turbo upgrade, an efficient intercooler, and precise ECU tuning is essential. In this guide, we break down each component and outline the path to a reliable 350-whp VA WRX.

Understanding Turbo Upgrades for the VA WRX

The factory VF-series turbocharger on the VA WRX is designed for a conservative power band, prioritizing emissions and fuel economy. It reaches its flow ceiling well below 350 whp, forcing the engine to run higher boost with less efficiency. A turbo upgrade addresses the fundamental bottleneck by moving more air volume at lower pressure, reducing heat and stress while increasing power.

What a Turbo Upgrade Changes

  • Airflow capacity: Larger compressor and turbine wheels allow the engine to ingest more air per revolution.
  • Boost response: Upgraded turbos can be matched to spool characteristics that suit your driving style (quick spool for street, top-end for track).
  • Thermal efficiency: Modern billet wheel designs improve compressor efficiency, lowering charge air temperatures.

Stock Turbo Limitations and Why Upgrade?

Pushing the stock turbo beyond its efficiency island (typically around 21–22 psi) results in diminishing returns: high intake air temperatures, excessive backpressure, and potential for pre-ignition. For 350 whp, the stock unit simply cannot deliver the airflow required. Upgrading also unlocks the potential of other modifications like E85 fuel or larger injectors, because the turbo can supply the volume those changes demand.

The 350 HP Goal: What It Really Takes

350 whp (approximately 400–420 crank horsepower) is an aggressive yet reliable target for a street-driven VA WRX. It requires careful part selection and professional tuning. Here is a realistic look at the essential components:

  • Turbocharger: A garrett-based or OE-quality upgrade sized for 350–400 whp (e.g., Blouch 1.5XTR, FP Blue, or EFR 6758).
  • Intercooler: A front-mount intercooler (FMIC) or a high-flow top-mount (TMIC) with significantly larger core volume.
  • Fuel system: Upgraded injectors (1000–1300cc) and a high-flow fuel pump (e.g., AEM 340 or DW300c).
  • ECU tuning: A custom tune via Cobb Accessport or open-source software, ideally on a dyno for safety.
  • Supporting mods: A full 3-inch exhaust system (downpipe and catback), cold air intake, and an electronic boost controller.

Skip any one of these, and you risk leaving power on the table or, worse, damaging the engine. An engine management failure at this power level can be catastrophic.

Choosing the Right Turbo Upgrade

There is no single "best" turbo for a 350-whp VA WRX; the right choice depends on your driving habits, budget, and tolerance for spool lag. Broadly, upgrades fall into two categories: stock-location turbos and rotated (garrett-style) kits.

Stock-Location Options

Stock-location turbos bolt directly to the OEM exhaust manifold and use the factory oil/coolant lines. They are easier to install and remain CARB-legal in many cases. Popular choices include:

  • Blouch 1.5XTR: Excellent spool (full boost by 3500–3700 RPM), supports up to 380 whp on E85.
  • FP Blue: A classic Subaru upgrade, slightly laggier than the 1.5XTR but capable of 400+ whp with good top-end pull.
  • BorgWarner EFR 6758: Integrated recirculation and outstanding response; a favorite for daily-driven 350-whp builds.

Rotated (Garrett-Based) Kits

Rotated kits reposition the turbo away from the block, allowing for larger wheels and better flow. They typically require custom piping, a new downpipe, and aftermarket intercooling. Options like the IAG Performance Garrett stage 1 kit or a custom setup around a GT3076R can surpass 350 whp easily, but spool is heavier (full boost near 4000 RPM).

Key Selection Criteria

  • Spool vs. peak power: For street use, prioritize a turbo that reaches full boost by 3600–3800 RPM.
  • Install complexity: Stock-location turbos are DIY-friendly; rotated kits demand fabrication skills.
  • Future headroom: If you plan to go beyond 400 whp later, choose a turbo that can grow with you (e.g., EFR 7163).

Upgraded Intercoolers: Keeping Charge Air Cool

Heat is the enemy of power. When a turbo compresses air, it heats up significantly—losing density and increasing the chance of knock. An upgraded intercooler is not optional for a 350-whp build; it is a necessity. The VA WRX came with a top-mounted intercooler (TMIC), but its limited core size becomes a restriction once boost pressure rises.

Front-Mounted vs. Top-Mounted vs. Liquid-to-Air

  • Front-Mount (FMIC): Mounted in the front bumper, exposed to direct airflow. Offers the best thermal capacity for sustained WOT runs. Recommended for 350+ whp because it reduces intake air temperatures (IAT) by 30–50°F compared to stock. Brands like Process West and Turbosmart make specific VA-WRX FMIC kits with complete piping.
  • Top-Mounted (TMIC): Retains factory placement and shorter piping (better throttle response). High-flow TMICs like the Grimmspeed or COBB TMIC can cool well for up to 400 whp on the street, but they are prone to heat soak on hot days or during track use.
  • Liquid-to-Air (L2A): A liquid-to-air intercooler system uses a coolant loop and a remote heat exchanger. It offers very low intake tract volume and consistent IATs, but adds complexity and cost. Rare on the VA WRX but effective for serious builds.

What to Look For in an Intercooler

  • Core volume: Look for 40–50% larger than stock. For FMICs, a core around 4″ thick by 12″ tall by 24″ wide is typical for 350–400 whp.
  • Pressure drop: A well-designed core should have less than 1 PSI drop at your target boost. Beware of cheap cores that flow poorly.
  • Bar-and-plate vs. tube-and-fin: Bar-and-plate is more durable and transfers heat better for street/highway driving; tube-and-fin is lighter and works well on the track but can bend easier.

Installation tip: When upgrading to an FMIC, you may need to trim the bumper beam or install a crash bar with integrated intercooler brackets. Plan accordingly for your 350-whp budget.

ECU Tuning: The Linchpin of Reliability and Performance

Adding a larger turbo and intercooler without proper calibration is a recipe for engine failure. The stock ECU can compensate for small changes, but it cannot handle the radically different airflow and fuel requirements of a 350-whp build. Tuning recalibrates fuel maps, ignition timing, boost targets, and knock detection strategies to make the engine safe and responsive.

Why Professional Tuning Is Non-Negotiable

A 350-whp VA WRX runs about 18–22 PSI of boost (depending on turbo and fuel), with significantly higher cylinder pressures. Without a custom tune, you risk:

  • Knock and detonation: Stock timing curves are too aggressive for the heat generated by larger turbos. Tuning pulls timing and enriches the mixture to mitigate knock.
  • Lean conditions: Larger turbos flow more air than the stock MAF and injectors can report. A tune scales the fuel tables to match.
  • Boost spikes: The stock electronic boost control may overshoot with a larger turbo. A tuned map uses duty cycle adjustments to maintain stable boost.

Tuning Platforms for the VA WRX

  • Cobb Accessport (V3/V4): The most common option. You can purchase off-the-shelf (OTS) maps from Cobb or other tuners, but for a 350-whp build, a custom dyno or e-tune from a reputable Subaru tuner (e.g., BrenTuning, P&L Motorsports, Driveline Motorsports) is strongly recommended. OTS maps are generic and often leave power on the table.
  • Open-source tuning (ECU flash via Tactrix): More cost-effective but requires familiarity with software like RomRaider and a wideband O2 sensor. Gives you full control and is popular among dedicated DIYers.
  • Flex Fuel (E85): Adding a flex fuel sensor and tune for E85 dramatically increases octane and cooling. On a 350-whp build, E85 can yield an additional 30–50 whp with zero extra hardware—as long as the fuel system can handle the flow.

Tuning Process Steps

  1. Baseline log: Record data logs of the stock car to ensure it’s healthy before modifications.
  2. Install hardware: All parts should be on the car and leak-free. The tuner needs the final hardware configuration.
  3. Dyno or street tuning: The tuner adjusts fuel, timing, boost, and knock settings while monitoring wideband AFR, knock correction, and EGTs.
  4. Final logs: Verify the tune under load in real-world conditions. Adjust cold-start and idle maps for drivability.

Expect to pay $500–$1,000 for a custom dyno tune, which is cheap compared to the cost of a blown motor.

Supporting Mods: The Foundation for 350 WHP

Even with the perfect turbo, intercooler, and tune, your VA WRX will need a supporting cast of modifications to reach 350 whp reliably.

Fuel System

  • Fuel injectors: Stock injectors run out of flow around 300 whp. Upgrade to 1000–1300cc high-impedance injectors (e.g., Injector Dynamics, FIC, or DW).
  • Fuel pump: A drop-in high-flow pump (AEM 340 or DW300c) ensures pressure doesn’t drop under high load. For E85, consider a dual pump setup.
  • Fuel lines: Stock lines are capable for 350 whp, but ensure the pressure regulator is functioning. Some builds add a return line for more consistent fueling.

Intake and Exhaust

  • Cold air intake (CAI): A good intake (COBB, Grimmspeed, AEM) reduces restriction and adds a noticeable induction noise. Ensure it includes a proper heat shield to keep IATs down.
  • Downpipe: A high-flow catted or catless downpipe is essential. It reduces backpressure significantly, allowing the turbo to spool faster and make more power. The VA WRX downpipe is notorious for its restrictive stock catalytic converter.
  • Catback exhaust: A 3-inch catback system complements the downpipe; optional but recommended for flow. Keep in mind that catless setups may not pass emissions in some regions.

Boost Control

The factory boost control solenoid (BCS) can be inaccurate at higher boost levels. An electronic boost controller (EBC) like the Cobb 3-Port or Grimmspeed MBC gives the tuner finer control over boost response, reducing overshoot and improving drivability. For a 350-whp build, a 3-port EBC is a common upgrade.

Engine Management & Cooling

  • Engine oil cooler: After sustained high-load pulls, oil temperatures can exceed 240°F. An oil cooler (Setrab, Mishimoto) is a wise investment for track use.
  • Radiator: The VA WRX stock radiator is adequate for 350 whp on the street, but a larger aluminum unit (Koyo, Mishimoto) helps on hot days or during canyon runs.
  • Bypass valve: The stock plastic bypass valve may leak under high boost. Upgrade to a forged metal unit (TurboXS, GFB).

Installation Tips and Common Pitfalls

A well-planned installation saves time and money. Here are practical tips gleaned from the Subaru community.

  • Do not use cheap parts: eBay turbos and intercoolers often have poor quality control, poor flow, and can send debris into your engine. Stick with reputable brands (Blouch, Garrett, Process West, Grimmspeed).
  • Pre-turbo exhaust leaks: Any exhaust leak before the turbo will cause boost creep and make tuning difficult. Use new gaskets and double-check the turbo to up-pipe connection.
  • Oil supply and drain: Ensure the oil drain line is properly angled and not kinked. A restricted drain can cause turbo seal failure. Use a high-quality synthetic oil (5W-30 or 5W-40).
  • Heat management: Wrap the downpipe and turbo in heat wrap or install a turbo blanket to reduce under-hood temperatures. This also protects nearby wiring and coolant hoses.
  • Boost leak test: After installation, pressurize the intake system to 25 PSI and look for leaks. A simple PVC cap and air compressor fitting can be used—leaks rob power and can cause knock.
  • Professional help: If you are not comfortable with welding or wiring a boost controller, pay a shop familiar with Subaru builds. The cost saves you from headache and potential engine damage.

Achieving 350 HP: Step-by-Step Parts List

For a proven, reliable 350-whp VA WRX, here is a sample parts list. Prices are approximate and vary by vendor.

  • Turbo: Blouch 1.5XTR or FP Blue – $1,800–$2,200
  • Intercooler: Process West Verti-Cooler FMIC kit – $1,000–$1,500
  • Fuel system: Injector Dynamics 1050cc, AEM 340 pump, flex fuel sensor – $800–$1,200
  • Tuning: Cobb Accessport V3 + custom dyno tune – $650 + $600
  • Exhaust: Cobb catted downpipe + Grimmspeed catback – $1,200–$1,500
  • Intake: COBB SF intake with box – $350
  • Boost control: Grimmspeed 3-port EBC – $150
  • Misc: Turbo blanket, gaskets, fluids – $200

Total: Approximately $6,000–$7,500 in parts. Budget another $1,000–$1,500 if paying a shop for installation.

Conclusion: A Proven Platform for Street-Tuned Power

Reaching 350 whp in a VA WRX is not a pipe dream—it’s a well-traveled path with clear, proven components. The key is balance: a properly sized turbo that spools efficiently, an intercooler that keeps charge air cool under sustained load, and a precise ECU tune that respects the engine’s limits. Avoid the temptation to cut corners on cheap parts or skip the custom tune. By investing in quality upgrades and taking the time to install them correctly, you’ll have a VA WRX that is both thrilling to drive and robust enough to enjoy for thousands of miles. Whether you choose a stock-location Blouch or a rotated Garrett kit, do your research, consult with experienced tuners, and always log your data. The 350-hp VA WRX is a reliable, daily-drivable machine—when built the right way.