The pursuit of more power from the Subaru FA20 engine—the 2.0L flat-four that powers the GR86/BRZ—has led many enthusiasts to forced induction. Among the most popular and proven options is the HKS GT Turbo Kit. This article breaks down the real-world power gains, dyno-proven results, and the supporting modifications needed to safely extract over 300 horsepower from the humble 2.0L boxer.

Understanding the GR86 2.0L Engine Platform

The first-generation Subaru BRZ and Scion FR-S (often collectively referred to as the GR86 family) debuted with a naturally aspirated 2.0L flat-four engine, the FA20. In stock form, it produces roughly 200–228 horsepower at the crank (depending on model year and tuning). The engine is known for its low center of gravity, excellent chassis balance, and high-revving nature, but its torque output—just 156–184 lb-ft—leaves many drivers wanting more punch from a stop or during highway passing.

Because the FA20 was designed from the outset with forced induction in mind (the block, rods, and crank are shared with turbocharged Subaru engines), it responds remarkably well to boost. The HKS GT Turbo Kit capitalizes on this inherent strength, delivering a reliable and repeatable power increase when paired with proper tuning and supporting modifications.

HKS GT Turbo Kit Overview

HKS is a Japanese tuning giant with decades of experience building turbo systems for Subaru boxer engines. The GT Turbo Kit for the FA20 is a complete bolt-on solution that includes everything needed to add a single Garrett GT-series turbocharger to the engine bay.

What’s Included in the Kit

  • Garrett GT2860RS turbocharger – a ball-bearing turbo known for quick spool and linear power delivery
  • Cast iron exhaust manifold – designed to reduce cracking and fitment issues common with tubular manifolds
  • Front-mount intercooler (FMIC) core and piping – keeps intake air temperatures in check
  • Tial blow-off valve – pre-assembled and plumbed into the intake tract
  • Oil supply and return lines – for proper lubrication and drainage
  • Intake piping and air filter – includes a heat-shielded intake to minimize heat soak
  • All necessary gaskets, bolts, and silicone hoses – for a comprehensive install

Key Design Features

  • Compact packaging – the kit fits without cutting the chassis or relocating the battery
  • Plug-and-play oil system – uses an adapter plate that replaces the factory oil filter sandwich
  • Dual wastegate options – supports both internal (standard) and external wastegate configurations
  • Intercooler piping sized for 300–400 whp – leaves headroom for future upgrades

Real Dyno Results: Power and Torque Gains

The most common question is simple: “How much horsepower does the HKS GT Turbo Kit add?” Dyno numbers vary slightly based on fuel quality, elevation, and tune aggressiveness, but the following figures represent consistent results reported by multiple shops and owners.

Stock Baseline (STD Correction)

  • Wheel horsepower: 175–190 whp
  • Wheel torque: 145–160 lb-ft

HKS GT Turbo Kit + 91/93 Octane Pump Gas (7–9 psi boost)

  • Wheel horsepower: 280–310 whp
  • Wheel torque: 260–290 lb-ft

HKS GT Turbo Kit + E85 Flex Fuel (10–12 psi boost)

  • Wheel horsepower: 320–360 whp
  • Wheel torque: 300–330 lb-ft

At the crank, this translates to approximately 330–420 horsepower, depending on the drivetrain loss calculation. The torque curve flattens significantly compared to the stock engine, with peak torque arriving as early as 3,500 RPM and holding strong past 6,000 RPM. This completely transforms the driving experience, giving the car the low-end grunt it inherently lacked.

For reference, an independent dyno test by Delicious Tuning recorded 298 whp and 272 lb-ft on 91 octane pump gas, while FT86Club forum members regularly report 310–325 whp on E85 with a proper tune.

Quarter-Mile and Acceleration Improvements

Adding 120–150 wheel horsepower dramatically changes the car’s straight-line performance. Here are real-world results from owners who have installed the kit and recorded times:

  • 0–60 mph: drops from 6.2–6.5 seconds to 4.2–4.6 seconds (traction-limited on street tires)
  • Quarter-mile: stock high-14s to low-15s at 92–96 mph → 12.8–13.2 seconds at 108–112 mph
  • 60–130 mph: improves from 17–18 seconds to roughly 11–12 seconds

These numbers assume a manual transmission, adequate tires (200 TW or stickier), and a driver mod. With drag radials and a well-sorted suspension, some owners have dipped into the high-11-second quarter-mile range on E85 and higher boost.

One particularly telling metric is the mid-range pull. On a highway on-ramp, the car now has enough torque to overtake traffic without downshifting. The ball-bearing Garrett turbo spools quickly and provides smooth, linear power delivery that feels OEM+ rather than aggressive.

Supporting Modifications for Maximum Reliability

While the HKS GT Turbo Kit is designed as a bolt-on upgrade, squeezing every bit of power safely requires careful attention to supporting components. Skimping on these mods can lead to engine knock, fuel starvation, or excessive heat.

Fuel System Upgrades

Above 300 whp on pump gas, the factory fuel injectors and fuel pump begin to run out of headroom. For reliable operation, most tuners recommend:

  • Upgraded high-pressure fuel pump (HPFP) – an aftermarket unit from Nostrum HP or a DW650c in-tank pump
  • Flex fuel sensor and injectors – if running E85, 750–1,000 cc injectors are needed
  • Return-style fuel system – optional but recommended for big power builds (400+ whp)

Engine Management and Tuning

The HKS kit does not include a standalone ECU. You will need either:

  • ECU flash tune via ECUTek – the most common approach, offering full control over timing, fuel, and boost
  • HKS F-CON IS – a piggyback unit compatible with HKS’ own tuning ecosystem
  • Standalone ECU – like a MoTeC or Haltech, for maximum customization (overkill for most street cars)

Professional tuning by a shop familiar with the FA20 platform is non-negotiable. A poor tune can destroy the engine in minutes, especially with the increased cylinder pressure from forced induction.

Cooling and Exhaust

  • Oil cooler – the stock oil cooling system is marginal even without a turbo; a set-air oil cooler is highly recommended
  • High-flow catalytic converter or catless front pipe – the factory catalytic converter restricts exhaust flow, so a 3-inch cat-back exhaust is almost mandatory
  • Radiator upgrade – an aluminum cross-flow radiator helps maintain consistent coolant temperatures during spirited driving

Installation and Tuning Considerations

Installing the HKS GT Turbo Kit is not a beginner-level job. Plan on 15–25 hours of labor if doing it yourself, or roughly $1,500–$2,500 at a reputable shop. The kit fits without major chassis modifications, but there are some important steps:

  • Oil pan removal – the oil drain line requires welding a -10 AN bung into the oil pan (some kits include a pre-welded pan)
  • Drilling and tapping – for the oil supply line from the block
  • Intercooler piping routing – the FMIC requires removing the crash bar’s lower reinforcement, but the bumper cover fits without cutting
  • Boost control – the kit includes a manual boost controller; consider an electronic boost controller for safer, more consistent boost levels

Tuning costs range from $500–$1,200 for a baseline calibration (including dyno time) plus $200–$400 for a flex fuel calibration. Expect to pay extra if you want remote tuning or a custom e-tune.

Cost vs. Value: Is the HKS GT Kit Worth It?

The HKS GT Turbo Kit itself retails for around $4,200–$4,800 (depending on the version and included options). When you factor in supporting mods, labor, and tuning, the total investment to get a properly running 300+ whp setup typically falls between $7,000 and $10,000. For context, a supercharger kit from Edelbrock or Harrop may cost less upfront, but the turbo system has higher peak power potential and a more linear delivery.

Considering that a stock GR86/BRZ can be found used for under $25,000, spending $8,000 to nearly double the wheel horsepower is a compelling value. The car retains its handling balance, weighs only about 2,800 lbs, and now has enough power to embarrass much more expensive machinery.

Potential Downsides and Reliability

No performance modification is without compromises. Owners should be aware of:

  • Increased heat – the FA20’s coolant and oil temperatures will climb under sustained boost; an oil cooler and possibly a coolant reroute are strongly advised
  • Clutch upgrade – the stock clutch will slip at 300+ whp after a few hard launches; plan on an upgraded clutch and lightweight flywheel (budget $600–$1,200)
  • Emissions compliance – removing the stock catalytic converter may violate local laws; check regulations before purchasing
  • Insurance premiums – be upfront with your insurer about the modifications to avoid claim denials

Reliability, however, is generally good when the kit is properly installed and tuned. The factory FA20 block can handle 350–380 whp on a conservative tune without internal upgrades. Beyond that, forged rods and pistons become necessary.

Conclusion

The HKS GT Turbo Kit is one of the most effective and well-engineered bolt-on turbo solutions for the GR86/BRZ 2.0L engine. Real-world dyno results consistently show gains of 100–150 wheel horsepower on pump gas and up to 180 whp on E85, transforming the car from a momentum-oriented sports car into a genuine thrill machine with sub-13-second quarter-mile capability.

Success depends on supporting upgrades—fuel system, tune, cooling, and clutch—as well as an honest assessment of your budget and mechanical ability. When everything is dialed in, the HKS turbocharged FA20 delivers a driving experience that rivals cars costing twice as much. For enthusiasts seeking proven, repeatable power from the 2.0L boxer, the HKS GT Turbo Kit remains a top-tier choice.