Why Upgrade Your Forester Turbo?

Your Subaru Forester’s factory turbocharger is a finely tuned compromise between reliability, emissions compliance, and everyday drivability. As the engine ages or your performance expectations grow, the stock turbo often becomes a bottleneck. An upgrade unlocks significant horsepower and torque gains, improves throttle response, and can even enhance fuel economy under light load if properly tuned. For enthusiasts looking to extract more from their boxer engine, selecting a turbo from a trusted manufacturer is the first critical step. Below, we dig into three brands that consistently deliver high-quality hardware: BorgWarner, Garrett, and Precision.

BorgWarner Turbochargers

BorgWarner is a global leader in turbocharging technology, supplying original equipment to many automakers and aftermarket performance lines. Their engineering heritage, particularly with the EFR (Engineered for Racing) series, has made them a go-to choice for Subaru owners who want spool characteristics closer to a larger turbo without sacrificing daily manners.

Why BorgWarner Works for the Forester

The EJ and FA engine families in the Forester benefit from BorgWarner’s advanced aerodynamics. The company’s exclusive use of gamma-Ti (titanium aluminide) turbine wheels in many EFR models reduces rotational inertia, cutting spool time by as much as 15-20% compared to traditional Inconel wheels. This means you get meaningful boost sooner, ideal for a street-driven SUV.

Key Features

  • Variable Geometry Turbine (VGT): BorgWarner’s VGT technology varies the angle of turbine vanes to optimize exhaust flow across the rpm band. While more common on diesels, some aftermarket EFR turbos incorporate similar principles for broader power delivery.
  • Integrated Wastegates: Many EFR units feature a compact, ported internal wastegate that eliminates the need for an external gate on milder builds, simplifying installation and reducing cost.
  • Dual Ball Bearing Cartridge: Low friction and high durability allow these turbos to live longer at higher shaft speeds.
  • Speed Sensor Ready: EFR turbos come with a sensor port for monitoring turbine speed, a safeguard against overspin that’s valuable during aggressive tuning.

The EFR 6758 is a popular choice for those aiming at 350-400 whp with quick spool. For more power (450-550 whp), the EFR 7670 or EFR 8374 offer headroom but require upgraded fuel systems and engine internals.

Pros and Cons

  • Pros: Excellent spool, robust construction, integrated features reduce complexity, broad powerband.
  • Cons: Higher initial cost than some competitors, limited availability of specific turbine housings to fit Subaru uppipes.

Learn more about BorgWarner EFR turbos on their official site.

Garrett Turbochargers

Garrett Motion (formerly Honeywell Turbo Technologies) has been a cornerstone of the performance turbo market for decades. Their G-Series and GTX lineups are widely used in everything from daily drivers to race cars. For the Forester, Garrett turbos offer proven reliability and a massive support network, meaning parts, rebuild kits, and tuning resources are easy to find.

Why Choose Garrett for Your Forester

Garrett’s extensive OE experience translates into aftermarket turbos that are highly tolerant of abuse. Their GTX Gen II range, in particular, incorporates a ported shroud compressor housing that extends the compressor map’s flow range, reducing surge at high pressure ratios—a common issue when pushing a small turbo on a Subaru.

Key Features

  • Ball Bearing Technology: Garrett pioneered the use of ball bearing cartridges in automotive turbos. Their latest double ceramic ball bearings reduce friction by ~50% over journal bearings, cutting spool time by up to 2000 rpm in some applications.
  • Billet Compressor Wheels: The GTX line uses fully machined billet aluminum wheels for superior aerodynamic efficiency over cast wheels.
  • Advanced Aerodyne Aerodynamics: Garrett’s CFD-optimized blade profiles deliver higher flow density, meaning more air molecules enter the engine per revolution.
  • Oil-Cooled and Water-Cooled: Many models include both oil and water circulation for extended bearing life, especially important in hot climates or after repeated pulls.

A GTX2860R Gen II is a favorite for quick-spooling builds aimed at 300-380 whp. For 400-500 whp, the GTX3076R Gen II provides a good balance of lag and top-end. The GT3582R has long been the standard for high-horsepower Street Forester builds, power levels often exceeding 600 whp with supporting mods.

Pros and Cons

  • Pros: Massive aftermarket support, extensive tuning maps available, durable even under high EGT, wide range of A/R and flange options.
  • Cons: Some older GT models still use journal bearings, which lag behind modern ball-bearing designs; top-tier GTX models can be expensive.

Explore Garrett’s G-Series and GTX lineup on their performance portal.

Precision Turbochargers

Precision Turbo & Engine has built a reputation in the hardcore performance and motorsports arena. Their turbos are engineered from the ground up for maximum airflow at high boost levels, making them a favorite for drag racing, time attack, and other extreme use. For a Forester owner who wants to push the limits—perhaps building a track-day SUV or a high-horsepower daily—Precision offers some of the most aggressive options.

Why Precision Stands Out

Precision focuses on high-efficiency wheels and lightweight turbine designs that minimize rotational mass. Their Gen 2 and Gen 3 lines use proprietary CAD-optimized compressor housings with anti-surge slots and extended tip treatments that allow them to move huge volumes of air without choking at low rpm.

Key Features

  • High-Flow Turbine Design: Precision’s “Super Core” series uses a larger, more aggressive turbine blade profile that increases exhaust mass flow capacity by up to 15% over competitors at the same A/R.
  • Customizable Options: They offer interchangeable compressor covers, turbine housings in multiple A/Rs, and even custom billet wheel configurations. This allows a Forester owner to tailor the turbo to their exact engine combination—a huge advantage for custom builds.
  • Durable Components: All Precison ball-bearing units use high-temperature ceramic balls and upgraded retainers. Their Journal bearing options employ a proprietary oil wedge technology that extends life under high thrust loads.
  • Direct Fit Kits: Certain Precision models come with Subaru-specific inlet/outlet flanges and oil/coolant line adapters, drastically reducing fabrication work.

The Precision 5858 Gen 3 is a favorite for spool-friendly builds that still hit 400-450 whp. Those chasing 500-600+ whp often lean toward the 6266 Gen 3 or 6870 Gen 3, though these require larger injectors, upgraded fuel pumps, and often a built shortblock. For all-out race applications, the 8385 Gen 3 is used in Forester builds pushing well over 800 whp.

Pros and Cons

  • Pros: Exceptional top-end flow, robust build quality, excellent customer support, high-efficiency design reduces heat rejection.
  • Cons: Spool can be later than comparable BorgWarner or Garrett units if you select too large a model; they are often noisier due to the ported compressor cover; limited off-the-shelf direct fit kits for older Subaru models.

Check Precision Turbo’s current Gen 3 lineup on their website.

How to Choose the Right Turbocharger for Your Forester

With three excellent brands on the table, your final decision hinges on several factors. No single turbo is perfect for every Forester owner.

Performance Goals

If your goal is a responsive daily driver with 350-400 whp, a BorgWarner EFR 6758 or Garrett GTX2860R Gen II will give you the best drivability. For a track-oriented car that sees occasional street use, a Precision 6266 Gen 3 or Garrett GTX3076R strikes an ideal balance. If you’re building a full race car, look toward the larger Precision units or the BorgWarner EFR 8374.

Compatibility and Supporting Mods

All three brands require upgraded fuel delivery (injectors, fuel pump), a quality aftermarket intercooler (front-mount is recommended for anything over 400 whp), and proper engine management (ECU tuning via Cobb Accessport or open-source tools). The turbo flange pattern must match your up-pipe. Most Subaru applications use a T3 or T4 flange, but some Garrett turbos use proprietary divided inlets. Always verify before purchasing.

Budget and Availability

BorgWarner EFR turbos tend to be pricier, often $1800-$2500, but include integrated wastegates and intake pipes. Garrett GTX Gen II models range from $1400-$2000 for the core unit, but you must add actuator and flange adapter costs. Precision Gen 3 units fall in a similar range, though custom configurations can climb higher. Also factor in the cost of a professional tune—$400-$800—to safely dial in the new hardware.

Installation and Tuning Considerations

Upgrading the turbo on a Forester is not a simple bolt-on affair. You will need to remove the intercooler, downpipe, heat shields, and often the up-pipe. Many owners also upgrade the oil feed and drain lines to ensure consistent lubrication. Pay special attention to the banjo bolts and restrictor size—too much oil pressure can destroy the turbo seals.

Tuning Is Non-Negotiable

Even if you install the same turbo the car came with, a tune is essential to optimize air/fuel ratios, ignition timing, and boost control. With an upgraded turbo, the ECU’s stock maps will be dangerously lean under boost. Use a reputable tuner familiar with Forester chassis (many specialize in Subaru WRX/STI tuning, but the Forester’s heavier weight and different gear ratios require tailored settings).

Oil and Coolant Lines

BorgWarner EFR units require a specific -4AN oil feed and -10AN drain, with coolant lines that can be adapted from the stock locations. Garrett GTX turbos typically use a standard -4AN feed with a push-loc drain, and many come with brass barb fittings for OEM-style coolant hoses. Precision provides detailed installation guides and often supplies adapter kits. If you are not comfortable with custom hoses, consider a direct-fit kit from a company like Full-Race, KillerB Motorsport, or IWire.

Long-Term Reliability and Maintenance

All three brands build turbos that last 100,000+ miles with proper care. Key longevity factors: use high-quality synthetic oil, change it every 3,000-5,000 miles, let the turbo cool down (idle 30 seconds after a hard drive), and run a quality catch can to reduce oil ingestion through the PCV system. Wastegate and boost controller maintenance is also critical—failure can cause overboost and engine damage.

Final Thoughts on Upgrading Your Forester Turbo

Your Forester is capable of transforming into a genuinely quick vehicle with the right turbo upgrade. BorgWarner leads in spool and integration; Garrett offers market-proven reliability and infinite tuning support; Precision delivers raw top-end power for the most ambitious builds. Match your choice to your driving style, your budget, and your willingness to support the turbo with properly matched mods. A well-researched upgrade paired with a professional tune will give you years of driving enjoyment and a Forester that outruns almost anything else in the dirt or on the street.

For further reading, explore Subaru-specific forums like SubaruForester.org or the NASIOC community, where countless Forester owners have documented their turbo upgrade journeys.