Understanding Forced Induction: Superchargers vs Turbochargers

Forced induction is the most effective way to significantly increase an engine's power output without increasing displacement. The Subaru BRZ's 2.0-liter FA20 engine is naturally aspirated from the factory, producing around 200 horsepower and 151 lb-ft of torque. For enthusiasts seeking more, the decision often comes down to supercharging versus turbocharging. While turbochargers use exhaust gases to spin a turbine, superchargers are mechanically driven via a belt connected to the crankshaft. This fundamental difference gives superchargers instant throttle response with no lag, making them ideal for drivers who want power on demand during corner exits or spirited driving. Additionally, supercharger kits for the BRZ are known for their comparatively simpler installation and more linear power delivery, closely mimicking the feel of a larger naturally aspirated engine.

Why Choose a 7psi Supercharger Kit for the BRZ?

A 7psi (pounds per square inch) supercharger kit represents a conservative yet rewarding boost level for the FA20 engine. It provides a substantial power increase—typically from 200 to 260–270 horsepower—while remaining within the safety margins of the stock engine internals, fuel system, and drivetrain. This makes it an attractive entry-level forced induction setup for daily drivers and weekend track enthusiasts alike.

Safe Boost Levels for Stock Internals

The BRZ's FA20 engine features a closed-deck block and forged connecting rods, which are capable of handling moderate boost levels. At 7psi, the cylinder pressures remain manageable, reducing the risk of ring land failure or rod bending—common issues at higher boost pressures. Most reputable tuners agree that 7psi is the maximum safe boost for a completely stock engine without requiring a built bottom end. This allows owners to enjoy a 30% power increase with minimal mechanical changes.

Components of a Typical 7psi Kit

A complete 7psi supercharger kit typically includes:

  • Supercharger unit (often a positive-displacement roots or twin-screw type from manufacturers like Edelbrock or Jackson Racing)
  • Air-to-air or air-to-water intercooler to reduce intake temperatures
  • Mounting brackets and hardware
  • Drive belt and pulleys with proper tensioning
  • Upgraded fuel injectors (often 550cc or larger) and a higher-flow fuel pump
  • ECU tuning solution (e.g., a reflash via software like COBB Accessport, or a standalone ECU)

High-quality kits are designed as bolt-on affairs, meaning they require no drilling or permanent modifications to the vehicle for installation.

Detailed Installation Process

Installing a 7psi supercharger kit is a weekend project for a skilled DIY mechanic, but professional installation is recommended for those without extensive experience. The process involves several detailed steps.

Preparation and Tools Required

Before starting, gather metric sockets, wrenches, torque wrench, coolant, oil, thread locker, and a scan tool for initial engine checks. It is also critical to have the tuning device and laptop with the calibration file ready. Work in a clean, well-lit area and allow the engine to cool completely.

Step-by-Step Overview

  1. Disconnect the battery and remove the engine cover, intake snorkel, air box, and radiator fans for access.
  2. Drain coolant partially and remove the radiator shroud and upper radiator hose to make room for the supercharger bracket.
  3. Install the supercharger mounting bracket onto the engine block using supplied bolts with thread locker. Torque to specifications.
  4. Mount the supercharger unit onto the bracket and attach the drive belt. Use a belt tension tool to achieve the correct tension.
  5. Install the intercooler and plumbing. This may involve cutting the factory plastic intake tube or replacing it with silicone hoses. Secure all clamps tightly.
  6. Upgrade fuel injectors and fuel pump (if required). For 7psi kits, larger injectors are usually included. Replace them carefully to avoid o-ring damage.
  7. Reassemble the cooling system — refill coolant, install new thermostat if recommended, and bleed air from the system.
  8. Double-check all connections — belts, hoses, wiring, and vacuum lines. Ensure nothing is loose or rubbing against moving parts.
  9. Upload the tuning file via the ECU flash tool. Follow the tuner’s instructions for initial startup and idle learning.

Tuning and Calibration

Tuning is the most critical aspect of a supercharger installation. Even a high-quality kit will not perform optimally without proper calibration. Most 7psi kits come with a base map that is safe for pump gas (91–93 octane). However, professional dyno tuning is highly recommended to dial in fuel and ignition timing for maximum power and safety. A well-tuned 7psi kit will produce smooth, linear power with no flat spots.

Quantifying Power Gains: From 200 to 260+ HP

The advertised 200-to-260 horsepower gain is realistic under ideal conditions. On a Dynojet chassis dynamometer, a stock BRZ typically reads 170–180 wheel horsepower (whp). With a 7psi supercharger and proper tuning, wheel horsepower climbs to around 230–240 whp. Assuming 15% drivetrain loss, that translates to approximately 270 crank horsepower—a 35% increase.

Horsepower and Torque Curves

Torque is equally transformed. Stock torque of 150 lb-ft at the wheels can rise to 200–210 lb-ft. More importantly, the torque curve is fattened across the mid-range. Whereas the naturally aspirated engine needs to be revved above 6,000 rpm for peak torque, a supercharged BRZ delivers 80% of peak torque from 3,500 rpm onward. This makes the car significantly quicker in everyday driving and on track.

Real-World Performance Improvements

The impact of these gains is immediately noticeable. 0–60 mph times drop from the stock 6.2 seconds to around 4.8–5.0 seconds. Quarter-mile times improve from 14.6 seconds to approximately 13.2 seconds at 105–108 mph. More importantly, corner exit speeds increase dramatically because the driver can apply throttle earlier without bogging. The supercharged BRZ feels like a completely different car—still nimble, but now with the straight-line punch to back up its cornering ability.

Reliability and Longevity Considerations

While a 7psi kit is considered safe, forced induction does add stress. Understanding the limits and required maintenance is essential for long-term reliability.

Engine Internals

The stock FA20 rods and pistons are adequate for 7psi, but the rod bolts are a weak point. Consider upgrading to ARP rod bolts if planning extended high-rpm use. The direct injection system requires periodic cleaning (walnut blasting) to prevent carbon buildup, which is accelerated by supercharger oil mist if the catch can system is insufficient.

Cooling System Upgrades

Increased boost raises intake and coolant temperatures. At a minimum, install an upgraded radiator (Koyo or Mishimoto) and an oil cooler to keep temperatures in check during hard driving. The intercooler included with most 7psi kits is sufficient for street use, but track rats may want a larger core or a water-methanol injection system.

Maintenance Schedule

Supercharger oil needs to be checked or replaced every 15,000–20,000 miles. Drive belts should be inspected for cracks and tension annually. Use high-quality synthetic oil (0W-20 or 5W-30) and change it every 3,000–5,000 miles. Because the engine now produces more heat, spark plug life is reduced; use one-step colder plugs (e.g., NGK LFR7AIX) and replace them every 20,000 miles.

Cost Analysis and Budgeting

A complete 7psi supercharger kit costs between $3,500 and $5,000 for the hardware alone. Installation labor adds another $800–$1,500 if performed by a shop. Professional tuning on a dyno typically costs $500–$800. Additional supporting mods—radiator, oil cooler, upgraded clutch, and better tires—can add $1,000–$2,500. A realistic total budget for a reliable 7psi BRZ build is around $6,000–$8,000. While not cheap, it is far less than the cost of a turbo swap or engine rebuild, and the results transform the car's character.

Supercharger installation will void the factory powertrain warranty. Check with your dealer or read the Magnuson-Moss Warranty Act—dealers must prove the modification caused a failure. Some insurance companies may raise premiums for forced induction; inform them to ensure coverage. Emissions legality varies by state; CARB (California Air Resources Board) approved kits (such as the Jackson Racing CARB kit) are available for street legality in California and other states that follow CARB rules.

Conclusion

A 7psi supercharger kit is the most cost-effective and reliable way to boost a Subaru BRZ's power from 200 to 260+ horsepower without compromising daily drivability. The combination of instant throttle response, linear power delivery, and minimal mechanical changes makes it an ideal upgrade for enthusiasts who want more thrilling performance while retaining the car's signature handling. By choosing a quality kit, following proper installation and tuning procedures, and committing to a slightly more intensive maintenance regimen, owners can enjoy a transformed driving experience that rivals far more expensive sports cars. For further reading and community experiences, consult resources like FT86club and professional tuner forums.