How Much Horsepower Can You Expect from a Garrett GT2871R Turbo on a Subaru BRZ?

The Subaru BRZ (and its twins, the Scion FR-S and Toyota 86) is famous for its balanced chassis, low weight, and razor-sharp handling. Its naturally aspirated 2.0-liter FA20 engine delivers roughly 200–205 horsepower at the crank—enough for enjoyable daily driving but leaving enthusiasts wanting more. Forced induction, particularly a turbocharger, is the most direct path to significant power gains. Among the popular turbo upgrades, the Garrett GT2871R stands out as a versatile, proven unit. But what horsepower can you realistically expect when bolting a "250hp" GT2871R turbo to a BRZ? This guide breaks down the numbers, the supporting mods required, and real-world results.

Note: The "250hp" rating often associated with the GT2871R refers to its baseline potential on a standard application. On a Subaru BRZ, with proper tuning and parts, this turbo can comfortably push well beyond that figure.

Understanding the Garrett GT2871R Turbocharger

The Garrett GT2871R is a journal-bearing turbocharger from the legendary GT28 series. It features a 71mm compressor wheel and a 60mm turbine wheel, housed in a compact frame that fits many engine bays without major clearance issues. Its reputation comes from a balance of quick spool (boost onset as early as 2,500–2,800 rpm on a 2.0L engine) and the ability to support power from around 250–350 wheel horsepower (whp).

  • Compressor: 71mm (GT28-based), capable of flowing enough air for 300+ whp.
  • Turbine: 60mm, designed for fast response on smaller-displacement engines.
  • Housing Options: Available in .64 A/R for quicker spool or .86 A/R for top-end power. Most BRZ builds favor the .64 for street use.
  • Max Efficiency: While often rated "up to 250 hp," the GT2871R can sustain 300–350 crank horsepower (260–300 whp) with proper tuning and premium fuel.

Garrett motion’s official specifications confirm the GT2871R is suitable for engines producing 150–350 hp, depending on configuration. For a BRZ, this makes it an excellent match for moderate street builds that don't require a full engine rebuild.

The Subaru BRZ Engine Platform – Stock Capabilities and Limits

The FA20 engine in the BRZ has a 12.5:1 compression ratio in naturally aspirated form. That high compression is great for efficiency but becomes a challenge under boost without careful tuning or lower compression internals. Key points:

  • Stock Internals: The cast pistons and rods are reasonably strong, often surviving 250–300 whp on a conservative tune with proper fuel. Beyond that, forged rods and pistons are recommended for reliability.
  • Direct Injection: The FA20 uses direct injection (DI), which offers fuel delivery control but can be a limiting factor for high boost. Adding port injection or upgrading fuel injectors is common for builds targeting over 300 whp.
  • Cooling: The stock intercooler (if using a turbo kit) must be upgraded; factory oil cooling may also need attention.

Many owners achieve 280–320 whp on stock internals with a Garrett GT2871R when coupled with good intercooling, a proper tune, and 93 octane (or E85). Beyond 350 whp, internal upgrades become mandatory for longevity.

Expected Horsepower Gains with the GT2871R on a BRZ

Realistic horsepower figures depend heavily on boost level, fuel quality, and supporting modifications. Here is what you can expect across different build tiers:

Stage 1: Low Boost / Minimal Supporting Mods (7–9 psi)

  • Power: 230–260 whp
  • Torque: 220–250 lb-ft
  • Requirements: Turbo kit with intercooler, basic tune on 93 octane, stock fuel system (with possible injector upgrade). Engine internals remain stock. Spool: full boost by ~3,000 rpm.
  • Notes: Safe, reliable, and drivable. A substantial improvement over stock (around +60–80 whp).

Stage 2: Moderate Boost / Common Street Build (10–13 psi)

  • Power: 270–310 whp
  • Torque: 270–300 lb-ft
  • Requirements: Fuel injector upgrade (e.g., 550cc or larger), aftermarket fuel pump, high-flow exhaust (catless downpipe, catback), larger intercooler, and a professional dyno tune. Stock internals can handle this level if the tune is conservative and knock is avoided. Boost comes in around 2,800 rpm.
  • Notes: This is the most common target for a bolt-on GT2871R build. Drivability remains strong with a broad torque curve.

Stage 3: High Boost / Full Supporting Mods (14–18 psi)

  • Power: 320–350 whp
  • Torque: 310–340 lb-ft
  • Requirements: Forged internals (rods, pistons), upgraded fuel system (port injection or larger DI injectors + low-pressure pump), E85 or race gas, upgraded clutch, upgraded cooling (radiator, oil cooler). Boost thresholds may be slightly delayed (3,000–3,200 rpm).
  • Notes: At this level, the GT2871R is at its efficiency limit. For sustained track use, a larger turbo (GT3071R or similar) may be preferable, but on the street, this makes for an insanely responsive and powerful BRZ.

It's important to parse the "250hp" rating: that figure is a conservative ranking by Garrett for a generic application. On a modern direct-injection boxer engine with good head flow and proper tuning, the GT2871R can flow enough air to produce 300+ whp. Always interpret manufacturer ratings as a baseline, not a hard cap.

Key Factors That Influence Final Horsepower Output

Even with the same turbo, no two BRZ builds produce identical numbers. Consider these variables when setting your expectations:

1. Engine Tuning (The Most Critical Factor)

No other single component matters more. A talented tuner can maximize power while keeping knock away. Conversely, a poor tune can leave 50–80 hp on the table or, worse, destroy the engine. Use a reputable shop with proven FA20 turbo experience. ECUTek is the most common tuning platform.

2. Fuel Quality and Octane

93 octane pump gas is sufficient for Stage 1/2 builds. E85 (flex fuel) offers a major advantage: higher knock resistance, allowing more timing advance and boost. Expect an additional 20–40 whp on E85 compared to 93 octane at the same boost level. Many Stage 3 builds rely on E85 to reach 350 whp safely.

3. Intercooler Efficiency

The stock intercooler (if part of a kit) is often undersized. Upgrading to a larger bar-and-plate intercooler reduces intake air temperatures (IATs), preventing knock and allowing consistent power. A good intercooler is essential for sustained pulls.

4. Exhaust Flow

A restrictive exhaust system creates backpressure that hampers turbo spool and power. A 3-inch downpipe and catback exhaust (or even a catless downpipe) will improve flow. Many owners report a 10–15 whp gain just from a catless downpipe with an otherwise stock exhaust.

5. Boost Pressure and Wastegate Spring

The GT2871R's .64 A/R housing can reach full boost by 2,800–3,000 rpm. Boost level is controlled by the wastegate and boost controller. Higher boost pushes more air but also generates more heat. For longevity on stock internals, keep peak boost under 12 psi. Forged internals allow 14–18 psi safely.

6. Intake and Turbo Inlet

A high-flow intake and a 2.5–3 inch turbo inlet pipe reduce restriction. The stock airbox can be restrictive; aftermarket options (e.g., Perrin, Cobb) are proven to yield small gains and quicker spool.

Real-World Dyno Results from BRZ Owners

Forums and tuning shops provide abundant examples of GT2871R-powered BRZ builds. Here are a few anonymized but representative data points:

  • Build A (Stock internals, 93 octane): 285 whp, 270 lb-ft at 11 psi. Supporting mods: injectors, fuel pump, intercooler, catless downpipe. Tuner noted knock limit reached; E85 would add ~25 hp.
  • Build B (Stock internals, E85): 318 whp, 310 lb-ft at 12 psi. Supporting mods: upgraded fuel system (DI + port injection), full exhaust, intercooler, intake. Extremely responsive; boost threshold near 2,800 rpm.
  • Build C (Forged rods/pistons, E85): 352 whp, 335 lb-ft at 16 psi. Supporting mods: port injection, twin oil coolers, upgraded radiator, race clutch. Tuner reported turbo nearing its compressor limit; still spools quickly.
  • Build D (Conservative low boost, stock internals): 250 whp, 240 lb-ft at 8 psi. This owner prioritized reliability and daily drivability. Result is a very safe, linear powerband perfect for autocross.

These examples illustrate the range. Most street-focused owners land between 280 and 310 whp—a massive improvement over stock's ~170 whp at the wheels—without sacrificing daily manners.

Potential Challenges and Considerations

Adding a GT2871R turbo to your BRZ is not without trade-offs:

  • Clutch Slippage: The stock clutch can't hold much more than 250 whp. Plan for a Stage 2+ clutch or twin-disc unit.
  • Heat Management: Turbocharging a boxer engine creates under-hood heat. Oil coolers, upgraded radiator, and heat-wrapping the downpipe are strongly recommended.
  • Fuel System Limitations: High-pressure fuel pump (HPFP) and direct injectors may struggle above 300 whp. Many tuners add port injection to supplement fueling.
  • Emissions and Legality: In many regions, turbocharging a modern car requires meticulous tuning to pass emissions. A catless downpipe may fail visual inspection.
  • Cost: A complete turbo kit plus install, tune, and supporting mods can easily exceed $7,000–$10,000. The GT2871R itself is affordable (~$800–$1,200), but the total package adds up.

Conclusion: How Much Horsepower Can You Expect?

With a Garrett GT2871R turbo on a Subaru BRZ, you can realistically expect between 280 and 350 wheel horsepower depending on boost, fuel, and supporting modifications. The "250hp" rating is a conservative baseline; on the FA20, this turbo is capable of much more. For most daily-driven builds, 300–320 whp hits a sweet spot of strong acceleration, reliable spool, and reasonable longevity of stock internals. If you're building a dedicated track car or chasing over 350 whp, consider a larger turbo, but for a responsive street monster, the GT2871R is hard to beat.

Always invest in professional tuning and quality supporting parts. The turbo is just one piece of the puzzle—proper fuel delivery, cooling, and engine management are what turn parts into power.

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Disclaimer: Modifying your vehicle carries risk. Always consult with a certified mechanic and tuner before pushing beyond stock power levels.