The Subaru BRZ and Toyota 86 are widely recognized for their exceptional chassis balance, low center of gravity, and tactile driving experience. However, the factory FA20 engine's power output is often described as adequate rather than thrilling. For enthusiasts seeking a substantial, reliable power increase, the HKS GT Supercharger kit remains a premier forced induction solution. Its reputation for high-quality engineering, linear power delivery, and robust hardware makes it a top choice. Nevertheless, a seamless upgrade requires more than just bolting on parts; it demands meticulous planning, technical precision, and a deep understanding of the vehicle's systems. This guide provides an authoritative, in-depth walkthrough designed to equip you with the knowledge necessary to execute the installation successfully and ensure long-term performance.

Evaluating the HKS Supercharger Ecosystem

Before disconnecting a single battery terminal, it is essential to understand exactly what the HKS GT kit offers and how it integrates with the BRZ platform. This knowledge forms the foundation for a successful build.

The HKS GT Centrifugal Design

Unlike positive displacement superchargers (Twin-Screw or Roots type) that provide instant, low-end torque, the HKS GT utilizes a centrifugal design. It operates much like a turbocharger driven by a belt. This configuration delivers power in a highly linear, progressive manner, building boost seamlessly with engine RPM. The result is a powerband that feels like a naturally aspirated engine with significantly more displacement, making it an excellent choice for both daily driving and track use where predictable power delivery is critical.

Kit Contents and Power Goals

A complete HKS Supercharger kit typically includes:

  • GT2 Supercharger Head Unit: The core component, known for its efficiency and durability.
  • Large Air-to-Air Intercooler: Essential for reducing intake air temperatures (IATs) and maintaining consistent power.
  • Dedicated Oil Cooler System: A critical component for track reliability, keeping the supercharger's internal temperatures in check.
  • High-Flow Fuel System: Usually includes upgraded fuel injectors and a higher-flow fuel pump to support the increased power demands.
  • Mounting Brackets, Pulleys, and Belts: Precision-machined components for a factory-like fitment.
  • Charge Pipes and Silicone Hoses: Designed to route the pressurized air efficiently with minimal restriction.

On a standard 93 octane tune, a Stage 1 HKS supercharger reliably produces 300-320 wheel horsepower (whp). Moving to Stage 2, which often includes an aftermarket header and an E85 fuel tune, can push output past 350 whp. It is critical to establish your power goals early, as this dictates supporting modifications and tuning requirements.

Pre-Installation: Essential Preparation

Proper preparation separates a smooth weekend install from a frustrating, drawn-out process. Do not skip these foundational steps.

Assessing Your BRZ's Baseline Condition

Adding boost puts significant stress on an engine. Performing a compression test and a leak-down test is non-negotiable. You need a healthy engine baseline. Pay close attention to the FA20's known issues, particularly the condition of the timing chain tensioner and the cleanliness of the intake valves. If the engine has high mileage or shows signs of wear, address those items before proceeding with forced induction.

Gathering Tools and Consumables

Beyond a standard socket set, the HKS install requires specific tools for a professional result:

  • Precision Torque Wrenches: You need both a ft-lb and an in-lb torque wrench for various fasteners to prevent over-tightening delicate components.
  • JIS Screwdrivers: Japanese Industrial Standard screws are common on the BRZ. Using a regular Phillips head often strips them.
  • Coolant Funnel and Vacuum Bleeder: Critical for properly bleeding the cooling system without introducing air pockets.
  • Supercharger Oil: HKS specifies a specific oil grade; ensure you have the correct fluid on hand.
  • T-Bolt Clamps: While the kit includes clamps, upgrading to high-quality T-bolt clamps on charge pipes provides superior hold and reduces the risk of boost leaks.

Workspace and Safety Protocol

Work on a level concrete floor. Ensure you have adequate lighting. Disconnect the battery and wait before working on any electronics. If you are using jack stands, ensure the chassis is stable on all four corners. Organize your hardware immediately in labeled bags to avoid confusion during reassembly.

The Installation Process: A Comprehensive Walkthrough

The installation itself is a multi-stage process. Working methodically is the key to avoiding mistakes.

Stage 1: Front Disassembly

Access to the engine bay and front of the car is required. This involves removing the front bumper cover, headlights, crash bar, and OEM radiator fan shroud. Take your time with the plastic clips and fasteners. This is also an excellent opportunity to upgrade to a lightweight aluminum radiator or an oil cooler for the engine itself, as access is wide open.

Stage 2: Mounting the Supercharger Bracket and Head Unit

The HKS bracket kit is stout and must be installed with precision.

  • Torque to Spec: Every bolt on the mounting bracket has a specific torque specification. Follow the HKS manual exactly. Over-torquing can distort the bracket, while under-torquing can lead to belt alignment issues.
  • Pre-Fill the Head Unit: Before bolting the supercharger to the bracket, manually rotate the drive pulley while pouring the specified amount of oil into the unit. This pre-lubricates the internal bearings and gears, preventing dry start damage.
  • Belt Alignment: Once mounted, check the belt alignment between the supercharger pulley and the crank pulley. It should be perfectly square. Misalignment is the primary cause of belt wear and noise.

Stage 3: Intercooler and Charge Piping

The intercooler mounts low in the front bumper support structure, receiving direct airflow.

  • Routing: Route the charge pipes carefully, ensuring they do not contact the hood, chassis, or any moving components. Friction will eventually wear a hole in the piping.
  • Clamping: Double-check all silicone couplers and T-bolt clamps. A single loose clamp after the MAF sensor will create a boost leak, causing poor performance and a dangerous lean condition.
  • Bypass Valve: The HKS kit includes a recirculating bypass valve. Ensure its vacuum line is connected securely to the intake manifold.

Stage 4: Fuel System and Ancillary Components

The kit includes upgraded injectors and a fuel pump. Installing a Flex Fuel Kit at this stage is highly recommended. Flex fuel allows you to run high ethanol content (E85), which provides significant knock resistance and allows for more aggressive ignition timing and boost targets. The labor is the same, and the future tuning flexibility is invaluable.

Stage 5: Final Checks and Fluid Fill

Before starting the engine, perform a final audit. Reconnect all electrical connectors, ensure the MAF sensor is installed correctly, and fill the cooling system using your vacuum bleeder to prevent air pockets. Fill the engine with high-quality full synthetic oil.

ECU Tuning and Calibration

This is the single most critical phase of the entire process. The physical installation is only half the battle; a proper calibration ensures the engine lives a long and powerful life.

Off-the-Shelf (OTS) Maps vs. Professional Tuning

While some base maps are available, they are often generic. A professional dyno tune or an E-Tune from a reputable specialist is strongly advised. A tuner can optimize the air/fuel ratio (AFR), ignition timing, and cam angle adjustment specifically for your car, fuel quality, and elevation.

The Role of Flash Tuning Software

Ecutek is the industry standard for the FA20 platform. It provides the ability to read and clear diagnostic trouble codes (DTCs), log data, and flash new calibration files to the ECU. A good Ecutek license and cable are mandatory.

Data Logging for Safety

Your tuner will ask for data logs. Key parameters to monitor include:

  • DAM (Dynamic Advance Multiplier): An indicator of overall knock health. It should stay at 1.000.
  • FLKC (Fine Learned Knock Correction) and FBKC (Feedback Knock Correction): These indicate knock events. Ideally, these remain at zero.
  • AF Learning 1 and AF Correction 1: These measure long-term and short-term fuel trims. They should stay within +/- 8%.
  • Boost Target vs Actual: Confirms your wastegate (or in this case, pulley ratio) is hitting the intended boost level.

Performing a few WOT (Wide Open Throttle) pulls in 3rd or 4th gear and sending these logs to your tuner is standard practice.

First Start and Break-In Procedure

The moment of truth requires patience and careful inspection.

Pre-Flight Checks

Spray a soapy water solution on all charge pipe connections while the engine is idling. Look for bubbles forming, which indicate a leak. Check the supercharger oil level and the engine oil level again. Listen for any unusual mechanical noises from the supercharger unit.

The Break-In Schedule

Do not immediately run the car at full boost. The supercharger's internal bearings and the belt need to seat properly.

  • First 100 miles: Drive gently, keeping the engine below 4,000 RPM and out of boost.
  • 100-300 miles: Vary engine speed. Perform a few moderate acceleration runs (5,000 RPM) to begin loading the system.
  • After 300 miles: Change the supercharger oil. This initial change removes any manufacturing debris and break-in particles.

Post-Installation Maintenance

A supercharged car requires a more rigorous maintenance schedule to ensure long-term reliability.

  • Supercharger Oil: Change it every 15,000 to 20,000 miles or annually, whichever comes first.
  • Belt Inspection: The supercharger belt sees immense stress. Inspect it for fraying, glazing, or cracks at every oil change. Replace it preventatively every 12,000 miles.
  • Intercooler Cleaning: Rocks, bugs, and salt can clog the intercooler core. A clogged core reduces efficiency and power. Gently wash it out with a low-pressure hose periodically.
  • Engine Oil: Shorten your oil change intervals to 3,000 to 4,000 miles. Use only a high-quality, full-synthetic oil that meets the FA20's requirements.

Frequently Asked Questions

Q: Is the HKS Supercharger kit CARB legal?
A: Yes, the HKS supercharger kit for the BRZ is typically CARB EO (Executive Order) approved, making it legal for street use in California and other states that follow CARB standards.

Q: Do I need to upgrade the clutch?
A: Absolutely. The factory clutch is designed for around 200 lb-ft of torque. At 300+ whp, it will slip almost immediately. A Stage 2 clutch kit (like those from ACT, Exedy, or South Bend Clutch) is a mandatory supporting upgrade.

Q: What happens if I install the supercharger and don't tune it?
A: The engine will not run correctly and can be destroyed in a matter of seconds. Forced induction requires a corresponding increase in fuel and controlled ignition timing. An untuned supercharged engine will run extremely lean, leading to detonation and catastrophic engine failure.

Q: How much power can the stock FA20 handle reliably?
A: On a proper tune and with good fuel, the FA20 has proven to be a robust engine up to around 350-400 whp. Beyond that, you are strongly advised to build the bottom end with forged rods and pistons.

Conclusion

Installing an HKS Supercharger on your BRZ is a journey that transforms the car into a truly potent performance machine. It requires patience, mechanical aptitude, and a strong respect for the engineering involved. By meticulously following the preparation steps, executing a clean physical install, and prioritizing a professional-grade tune, you ensure that your upgrade is not only seamless but also reliable for years of spirited driving. The reward is a beautifully balanced, gloriously powerful sports car that delivers an adrenaline-pumping experience every time you press the start button.