Introduction: From Factory Output to 350 Horsepower

For Subaru Legacy enthusiasts, the jump from a stock turbocharger to a serious aftermarket unit marks a turning point in the car’s identity. The factory turbo on a Legacy GT or Spec.B offers respectable performance, but it leaves significant headroom on the table. The FP Blue Turbo has emerged as the go-to upgrade for owners who want to cross the 350‑horsepower threshold without sacrificing the daily drivability that makes the Legacy a practical sports sedan. This article breaks down exactly what the FP Blue Turbo does, how it transforms the driving experience, and what it means for the car’s long‑term reputation and value.

What Is the FP Blue Turbo?

The FP Blue Turbo is a ball‑bearing, billet wheel turbocharger designed specifically for the Subaru EJ and FA engine families. Built by Forced Performance, it slots between the company’s entry‑level FP Green and the race‑oriented Red series. The “Blue” designation refers to the compressor housing finish and the specific compressor wheel design that prioritizes fast spool and high flow capacity.

Compared to the stock IHI or Mitsubishi units found on 2005‑2009 Legacy GT models, the FP Blue features:

  • A larger billet compressor wheel that moves more air at lower boost pressures, reducing the need for extreme boost levels to hit power targets.
  • Ball‑bearing center cartridge that cuts rotational friction dramatically, allowing the turbo to spool quicker than traditional journal‑bearing designs.
  • A redesigned turbine housing that improves exhaust gas flow and reduces backpressure at high rpm.

The result is a turbo that can produce 350‑370 wheel horsepower on pump gas with supporting modifications, while still offering street‑friendly spool characteristics. The FP Blue is frequently chosen for its ability to make power without sacrificing the mid‑range torque that makes the Legacy fun to drive in everyday traffic.

Power Gains and Performance Metrics

From Stock to 350 at the Wheels

A stock Legacy GT with a VF40 or VF46 turbo typically puts down 200‑220 wheel horsepower on a dyno. After a tune and basic bolt‑ons, that number climbs to 260‑280. The FP Blue Turbo, combined with proper fueling and tuning, pushes the Legacy into a completely different category: 350‑370 wheel horsepower on 93 octane, and up to 400 with ethanol blends.

This is not a peak‑number story. The power curve matters more than the headline figure. The FP Blue builds boost quickly, reaching 12‑14 psi by 3,000 rpm and full boost (18‑20 psi) by 3,800 rpm. It holds that boost all the way past 6,500 rpm, whereas the stock turbo runs out of breath after 5,500 rpm. The result is a flat torque curve that delivers consistent pull from 3,500 to redline, transforming the Legacy from a car that feels quick to one that feels genuinely fast.

Dyno Results and Real World Performance

Independent dyno tests from shops like Cobb Tuning and Turn In Concepts show the following typical gains with the FP Blue Turbo on a Legacy GT:

  • Stock turbo (VF40) – 220 whp, 235 wtq
  • FP Blue + supporting mods + 93 octane tune – 355 whp, 370 wtq
  • FP Blue + E85 flex fuel – 400 whp, 420 wtq

These numbers represent a 60‑80% increase in wheel horsepower. In the real world, that translates to a 0‑60 time in the 3.8‑4.0 second range and a quarter‑mile in the low 12‑second range for a properly sorted Legacy GT.

Installation Considerations

Preparation and Required Parts

Installing the FP Blue is not a weekend project for the complete novice, but it is well within the reach of a motivated DIYer with basic mechanical skills. You will need:

  • FP Blue Turbo kit (includes oil feed and drain lines, gaskets, and hardware)
  • Upgraded fuel system – larger injectors (at least 1,000cc), a high‑flow fuel pump (such as AEM 340 or DW300c), and possibly a fuel pressure regulator.
  • Full turbo‑back exhaust system – a downpipe with no catalytic converter or a high‑flow cat, plus a matching cat‑back.
  • Cold air intake – the stock airbox becomes a restriction above 300 hp.
  • High‑capacity intercooler – the stock top‑mount is inadequate; upgrade to a larger bar‑and‑plate unit by Process West or Spearco.
  • Tuning solution – either an Accessport with a custom tune, or a standalone ECU like a Haltech or Link.

Step‑by‑Step Installation Overview

The installation process follows a logical sequence, but careful attention to details prevents leaks and failures:

  1. Disconnect battery and drain coolant and engine oil.
  2. Remove the stock turbo – unbolt the exhaust manifold, disconnect the oil and water lines, and lift the unit out from underneath the car.
  3. Prepare the oil drain – the FP Blue uses a larger drain tube that requires enlarging the return hole in the oil pan or using a different pan.
  4. Install the new turbo – bolt the turbine housing to the manifold, connect oil feed and drain lines, and attach coolant lines.
  5. Mount the intercooler – the larger top‑mount unit requires trimming the hood scoop baffle or relocating the air conditioning lines.
  6. Install fuel system components – swap injectors, fuel pump, and rewire the pump for higher voltage if needed.
  7. Reprogram the ECU – load a base map and then perform a professional dyno tune to dial in ignition timing and fuel trims.

Allow a full weekend for the first installation, plus a few days for tuning. Many owners prefer to have a shop perform the work, but the DIY approach is feasible with the right tools and a service manual.

Supporting Modifications for Maximum Output

Fuel System Upgrades

350 wheel horsepower requires roughly 50% more fuel flow than stock. The factory fuel pump on a 2005‑2009 Legacy GT flows enough for about 280 wheel horsepower on the stock pressure regulator. At 350 hp, the pump cannot maintain pressure, leading to lean conditions and potential engine damage.

Install a Walbro 525 or AEM 340 pump, and upgrade to 1,000cc injectors or larger. For E85 capability, 1,300cc injectors and a flex fuel sensor are recommended. The fuel lines themselves are adequate, but the fuel pressure regulator should be changed to a unit that can hold pressure above 60 psi.

Intercooler and Intake

The FP Blue pushes significantly more heat into the intake charge than the stock turbo. An upgraded intercooler is not optional – it is mandatory to prevent detonation. A bar‑and‑plate top‑mount from Process West or a front‑mount kit from ETS will drop intake temperatures by 20‑40°F.

The intake track also needs attention. A short ram or cold air intake from K&N or AEM reduces restriction and allows the turbo to spool 200‑300 rpm sooner. Add a blow‑off valve or recirculation valve that can hold boost pressure above 20 psi without leaking.

Exhaust System

The stock exhaust system is a major bottleneck. The downpipe alone has a restrictive pre‑cat. Replace it with a 3‑inch catless downpipe and a matching mid‑pipe. Cat‑back systems from Invidia, HKS, or Greddy flow well and produce a deep, aggressive tone without being obnoxious at highway speeds.

Engine Management and Tuning

The stock ECU can be tuned via an Accessport with custom mapping, but the best results come from a session with a professional tuner who understands Subaru’s specific fuel and timing tables. Expect to pay $600‑$1,000 for a custom dyno tune. The tuner will adjust boost targets, fuel enrichment, ignition advance, and wastegate duty cycles to match the turbo characteristics.

A standalone ECU offers more control for extreme setups, especially with flex fuel or larger turbos, but for the FP Blue on pump gas, the Accessport is sufficient and retains features like cruise control and cold start logic.

Driving Experience and Everyday Usability

One of the most impressive aspects of the FP Blue conversion is how it transforms the driving experience without making the car undriveable. The stock Legacy GT feels responsive but runs out of steam above 4,500 rpm. The FP Blue delivers a steady surge of power all the way to redline, making highway passing effortless.

Turbo lag is minimal. The ball‑bearing core and smaller turbine housing choice (TD06SL2 8cm²) allow the turbo to reach positive boost by 2,800 rpm. In third gear at 60 mph, a stab of the throttle produces immediate acceleration, not a two‑second pause. The improved mid‑range torque means you do not have to downshift as often – the car pulls cleanly from 2,500 rpm in high gear.

Fuel economy suffers slightly at wide‑open throttle, but cruising on the highway at 70 mph still returns 25‑27 mpg if you keep your foot light. The tuning matters – a conservative tune that avoids overly rich mixtures will preserve daily‑driver fuel economy.

Long‑Term Reliability and Maintenance

Reliability is a legitimate concern when doubling horsepower output. The Subaru EJ25 engine is stout, but it has known weaknesses: ring land failure on pistons and oil starved turbo bearings. The FP Blue itself is a high‑quality unit, but the supporting systems must be robust.

Key maintenance practices for a 350 hp Legacy:

  • Oil changes every 3,000 miles with a high‑quality synthetic (5W‑30 or 5W‑40). The turbo’s ball bearings are sensitive to contamination.
  • Upgrade the oil pickup tube to a Killer B unit. The factory tube has been known to crack.
  • Monitor knock with a real‑time gauge. Even a small amount of detonation can destroy pistons quickly at higher boost levels.
  • Allow cooldown time – idle the engine for 30‑60 seconds after vigorous driving to let oil cool the turbo bearing.

With proper maintenance, the FP Blue conversion can last 50,000‑80,000 miles without major issues. Many owners report 100,000+ miles on their upgraded setups when they stick to a conservative tune and regular oil changes.

Impact on the Legacy’s Legacy

The Legacy chassis has always been a dark horse in the Subaru lineup – it lacks the aggressive styling of the Impreza WRX/STI but offers more interior space, a more comfortable ride, and understated looks. Adding the FP Blue turbo injects genuine performance credibility into that package.

Within the community, a Legacy GT that reliably produces 350 horsepower becomes a reference car. It demonstrates what the platform is capable of and commands respect at meets and track days. The car’s reputation shifts from “a mild sport sedan” to “a sleeper that can embarrass much more expensive machinery.”

Resale value is a mixed bag. A well‑built, documented FP Blue car with supporting mods and a professional tune can fetch a premium over a stock Legacy GT, especially among enthusiasts who understand the package’s capabilities. However, poorly executed modifications or a missing tune will tank the value. The key is to maintain a clean, reversible install and keep records of all parts and tuning sheets.

On a personal level, building a 350 hp Legacy is deeply satisfying. It is a car you can drive to work, take on road trips, and still run 12‑second quarter‑miles. That versatility is the real legacy.

Cost Analysis and Value Proposition

A complete FP Blue conversion – turbo, fuel system, intercooler, exhaust, and tune – costs between $4,000 and $6,000 in parts and labor. Compared to buying a faster car like a used STI or BMW 335i, the Legacy route offers a unique combination of utility and character. No other mid‑sized sedan from the mid‑2000s can match the Legacy’s ability to carry four adults and their luggage while running low‑12s.

The resale premium on a well‑built car can recoup 30‑50% of the mod costs. More importantly, the driving experience is irreplaceable – the FP Blue gives the Legacy a personality that stock cars lack, making every trip feel special.

Conclusion

Upgrading a Legacy with the FP Blue Turbo is one of the most rewarding modifications you can make to this platform. It delivers a genuine 350‑horsepower experience with excellent drivability, reliability, and a significant boost to the car’s reputation. By investing in proper supporting modifications and a quality tune, you create a vehicle that honors the Legacy name – not as a museum piece, but as a driver’s car that can still surprise people at every stoplight. The journey from stock to 350 hp is not just about the numbers; it is about redefining what your Legacy can be.