How Much Power Does a Precision 5857 Mini Turbo Add to Your Subaru BRZ? Up to 50 HP Gains Possible

The Subaru BRZ has earned a devoted following among driving purists thanks to its lightweight chassis, low center of gravity, and naturally aspirated boxer engine that delivers a balanced, engaging experience. Yet even the most enthusiastic owners eventually crave more power. For many, the most effective path to significantly higher output is forced induction. Among the turbocharger options available for the BRZ, the Precision 5857 Mini Turbo stands out as a compact, high-efficiency unit designed to work with the FA20 engine. When properly installed and tuned, this turbo can add up to 50 horsepower to the wheels, transforming the BRZ from a momentum car into a genuine performance machine. In this article, we will break down the real-world power gains, supporting modifications, installation considerations, and everything else you need to know about this popular upgrade.

Understanding Turbocharging on the BRZ Platform

Before diving into specifics, it is helpful to understand how turbocharging works and why it is particularly effective on the Subaru BRZ. The FA20 engine is a 2.0-liter naturally aspirated boxer four-cylinder producing roughly 200–205 horsepower at the crankshaft. Its high compression ratio (12.5:1) and port/direct injection system deliver excellent thermal efficiency but leave little headroom for power gains through bolt-on modifications alone. A turbocharger changes the equation by forcing compressed air into the intake manifold, allowing the engine to burn more fuel and produce more power per cycle.

The Precision 5857 Mini Turbo is a small-frame turbo optimized for quick spool and moderate boost levels, making it a strong match for the BRZ’s displacement. The “58” refers to the compressor inducer diameter (58mm), and “57” to the turbine exducer (57mm). The “Mini” designation indicates a compact housing that fits the tight engine bay of the BRZ without requiring extensive modification. With a maximum boost pressure around 20 PSI (depending on tuning and fuel), this turbo can reliably push the FA20 into the 250–300 wheel horsepower range on pump gas, and beyond with ethanol blends.

Specifications and Design of the Precision 5857 Mini Turbo

Precision Turbo & Engine has built a strong reputation for high-quality forced induction components, and the 5857 Mini is no exception. Key specifications include:

  • Compressor Wheel Diameter: 57mm inducer / 76mm exducer
  • Turbine Wheel Diameter: 53mm inducer / 57mm exducer
  • Compressor Trim: 76
  • Turbine Trim: 84
  • Maximum Boost Pressure: 20 PSI (higher with race fuel/e85)
  • Housing Options: T4 flanged turbine housing, available in different AR (0.63, 0.82, 1.04)
  • Bearing System: Journal bearing standard; ball bearing upgrade available for faster spool

The small turbine wheel and modest compressor size allow the 5857 Mini to spool quickly, reaching full boost by 3500–4000 RPM on a 2.0-liter engine. This makes it far more street-friendly than a larger turbo that would lag until higher revs. The unit is designed for engines producing 250–400 horsepower, which places the BRZ comfortably in its sweet spot. The Precision 5857 Mini is also known for its ability to maintain boost to redline without significant drop-off, providing a broad powerband that suits both daily driving and track use.

Realistic Power Gains: Dyno-Proven Results

The original article claimed “up to 50 HP gains” – and while that is possible, it is a conservative estimate. With a proper supporting package, the Precision 5857 Mini can add significantly more. Here is what real-world dyno tests show for a stock-bottom-end FA20 with appropriate mods:

  • Baseline (stock): ~170–175 whp (wheel horsepower) on a Dynojet
  • With Precision 5857 Mini, intercooler, injectors, and ECU tune at 10 PSI: ~240–250 whp (gain of 70–80 hp)
  • With 15 PSI on 93 octane pump gas: ~280–300 whp (gain of 110–130 hp)
  • With 20 PSI on E85 fuel: ~320–340 whp (gain of 150–170 hp)

Why the original article mentioned only 50 HP gains? That may refer to a very conservative “off-the-shelf” tune with minimal supporting mods. However, most enthusiasts who install this turbo will target at least 250–270 whp, which represents a jump of around 75–100 horsepower over stock. The 5857 Mini has enough headroom to push beyond 300 whp, but this requires upgraded fuel system components, a quality intercooler, and professional calibration. It is essential to manage expectations: every car is different, and actual gains depend on the condition of the engine, the quality of the tune, and the climate.

Factors That Influence Power Gains

Several variables affect how much power you will actually gain:

  • Boost level: More boost = more power, but increases stress on the engine.
  • Fuel quality: Higher octane or ethanol allows more ignition advance and boost without detonation.
  • Intake and exhaust restrictions: A free-flowing intake and 3-inch exhaust system help the turbo breathe.
  • Intercooler efficiency: A large, well-ventilated intercooler keeps intake temperatures low.
  • Tuning: A skilled tuner can extract maximum power while maintaining safety margins.

Most importantly, the stock FA20 has a cast aluminum block with closed-deck design, making it reasonably strong up to about 350 whp on a safe tune. Beyond that, forged pistons and rods are recommended. The Precision 5857 Mini is thus an excellent match for the stock bottom end when tuned conservatively.

Supporting Modifications: Building a Complete System

To achieve the power gains mentioned above, the turbocharger alone will not suffice. You need a carefully selected set of supporting modifications to ensure the engine receives adequate fuel, cool air, and proper exhaust flow. Below is a detailed breakdown of each component.

Fuel System Upgrades

The stock FA20 fuel system can handle approximately 250–260 whp on pump gas. Above that, you will need larger fuel injectors and possibly a high-flow fuel pump. Options include:

  • Injectors: 550-650cc/min (stock is around 215cc/min). Many use DeatschWerks or Injector Dynamics.
  • Fuel Pump: A Walbro 255 LPH or equivalent drop-in pump.
  • Flex Fuel Kit: For E85 users, a flex sensor and tune allows tuning for ethanol blends.

Intercooling System

Compressing air generates heat, and hot air reduces power and increases detonation risk. A front-mount intercooler (FMIC) is essential for sustained performance. Choose a core that is at least 24x12x3 inches with efficient bar-and-plate construction. Some kits integrate a blow-off valve and charge pipes. A quality intercooler can lower intake temperatures by 30–50°F, which directly translates to more power.

Exhaust System

The turbo’s turbine housing bolts to a downpipe, which must be at least 3 inches diameter to prevent backpressure. From there, a full 3-inch cat-back exhaust (with or without catalytic converter) will keep exhaust flow high. A high-flow catalytic converter or a test pipe (for off-road use) reduces restriction further. The stock BRZ exhaust is restrictive, so this is a mandatory upgrade.

Intake and Air Filter

A cold-air intake or short-ram intake with a high-flow filter ensures the turbo gets sufficient airflow. The Precision 5857 Mini typically uses a 4-inch inlet, so the intake should match. Many kits include a custom intake pipe and filter. Avoid restrictive paper filters; use a reusable cotton or foam cone filter.

Engine Management and Tuning

This is the most critical supporting mod. The stock ECU cannot properly control a turbocharger. Options include:

  • ECU Reflash: Companies like EcuTek or OpenFlash offer tuning solutions with custom maps.
  • Standalone ECU: Haltech, MoTeC, or AEM for full control (more expensive but allows advanced features).
  • Dyno Tuning: A professional dyno tune is highly recommended to dial in AFR, boost, and timing maps.

Without proper tuning, you risk engine damage. Budget for at least $500–1000 for a quality tune.

Installation Process and Considerations

Installing a Precision 5857 Mini Turbo on a Subaru BRZ is a significant undertaking. It requires mechanical skill, specialty tools, and a full weekend minimum. Here is an overview of the process:

  1. Remove stock intake, exhaust manifold, and front bumper cover. Access is tight; removing the bumper improves workspace.
  2. Install turbo mounting bracket and oil drain line. The kit usually includes a bracket that bolts to the engine block. Ensure proper oil drain angle to prevent coking.
  3. Mount the turbocharger. Bolt the turbine housing to the manifold or manifold adapter. Torque to spec.
  4. Install oil supply and return lines. Use a banjo bolt for the supply from the engine’s oil pressure port. The drain must run into the oil pan, requiring welding of a fitting or a pre-drilled pan.
  5. Attach intercooler and charge pipes. Mount the FMIC behind the bumper, route piping from turbo to intercooler to throttle body.
  6. Plumb the intake and blow-off valve. Connect filter and MAF sensor housing.
  7. Install downpipe and exhaust. Bolt downpipe to turbine outlet, connect to the rest of the exhaust.
  8. Wire boost controller and gauge. A manual or electronic boost controller is needed. Install a boost gauge to monitor pressure.
  9. Refill fluids and check for leaks. Use quality synthetic oil. Start engine, check for oil and coolant leaks.
  10. Initial startup and tuning. Do not drive hard until a base tune is loaded. Drive gently to the tuner.

Many owners choose to have the installation performed by a professional shop specializing in forced induction Subaru builds. Labor costs range from $1500 to $3000 depending on location and complexity. If you tackle the job yourself, expect 20–30 hours of work.

Common Installation Challenges

  • Oil drain clearance: The drain line must have a continuous downward slope. Some kits require modifying the oil pan.
  • Fitment near steering shaft: The BRZ’s engine bay is compact. Check clearances carefully when routing piping.
  • Intercooler piping: Some FMIC kits block the a/c condenser; you may need to relocate or trim brackets.

Reliability and Longevity

A properly installed and tuned Precision 5857 Mini turbo setup can be reliable for many miles. Key factors include:

  • Oil maintenance: Turbocharged engines require more frequent oil changes (every 3000–5000 miles) with synthetic oil.
  • Cool down: After hard driving, let the engine idle for 30–60 seconds to cool the turbo before shutdown. A turbo timer is optional.
  • Boost control: Do not exceed recommended boost levels. Sudden overboost can cause detonation and engine failure.
  • Engine internals: As mentioned, the stock bottom end is safe to about 350 whp. For 400+ whp, invest in forged rods and pistons.

Many owners have driven over 50,000 miles on stock internals with a 280–300 whp setup without issues, provided the tune is conservative and maintenance is diligent.

Cost Breakdown: What the Upgrade Really Costs

Budgeting for a turbo conversion goes beyond the price of the turbo itself. Here is a realistic estimate:

  • Precision 5857 Mini Turbo (kit): $1,600–$2,200 (including manifold, downpipe, lines, and hardware)
  • Fuel injectors and pump: $600–$900
  • Intercooler kit: $500–$800
  • Exhaust system (cat-back + downpipe): $600–$1,200
  • Intake: $200–$400
  • Boost controller and gauge: $200–$500
  • ECU tune (reflash + dyno): $500–$1,500
  • Labor (if not DIY): $1,500–$3,000
  • Miscellaneous (gaskets, fluids, fittings): $200–$400

Total estimated cost: $5,800 to $11,000. This may seem high, but for a gain of 100+ wheel horsepower, it is one of the most cost-effective ways to transform the BRZ’s performance. Compare that to a supercharger kit (often $4,000–$6,000 for less potential power) or a naturally aspirated build (expensive for small gains).

Comparison with Other Forced Induction Options

Supercharger Kits

Superchargers offer instant throttle response and linear power delivery. Kits like the Jackson Racing or Edelbrock produce around 250–270 whp on pump gas. They are easier to install and maintain, but top out at lower peak power compared to a turbo. The Precision 5857 Mini has the edge in ultimate horsepower potential (300+ whp) but requires more supporting mods.

Other Turbochargers

Larger turbos like the Garrett GT2860RS or Precision 6262 can produce 400+ whp, but spool significantly later, making them less enjoyable for street use. The 5857 Mini strikes a balance between quick spool and top-end punch. For a daily-driven BRZ that sees occasional track days, it is arguably the best all-around turbo option.

Conclusion

The Precision 5857 Mini Turbo is a well-engineered solution for Subaru BRZ owners who want a substantial power increase without sacrificing drivability. Real-world gains of 70–130 wheel horsepower are achievable with proper supporting modifications, making the original claim of “up to 50 HP” a very conservative floor. Whether you target 250 whp for a reliable street car or push toward 300+ whp with ethanol fuel, this turbo offers a broad powerband and proven reliability. The key to success lies in choosing quality components, investing in professional installation and tuning, and maintaining the car diligently. For anyone serious about unlocking the BRZ’s potential, the Precision 5857 Mini is a compelling upgrade.

For more information on the BRZ’s engine specifications, visit Subaru’s official BRZ page. For technical details on the turbocharger itself, check Precision Turbo’s product page. For community-driven tuning guides and dyno charts, Tuning Tech offers a comprehensive resource. And finally, for professional ECU calibration services, Engine Tuner provides custom tuning for the FA20 platform.