The Scion FR-S—sold elsewhere as the Toyota GT86 and Subaru BRZ—burst onto the scene as a pure, lightweight, rear-wheel-drive sports car that prioritized handling over straight-line speed. Its 2.0-liter flat-four boxer engine, co-developed with Subaru, delivers a modest 200 horsepower from the factory. That's enough to have fun, but most enthusiasts quickly start looking for more. The good news is that you don't need a five-figure budget to wake up this engine. A handful of smart, cost-effective modifications can unlock noticeable power gains and sharpen the driving experience without forcing you to eat ramen for a year. This article walks through the best bang-for-your-buck upgrades for the FR-S, explaining what each part does, what kind of gains to expect, and how they fit into a build that keeps your wallet intact.

Understanding the FA20 Engine and Its Potential

The FR-S uses Subaru's FA20D four-cylinder boxer engine. It's a 2.0-liter naturally aspirated unit with direct injection, a high 12.5:1 compression ratio, and a redline around 7,400 rpm. The boxer layout keeps the center of gravity low, which is excellent for handling, but the engine's tuning left a fair amount of performance on the table. Factory fuel maps are conservative, exhaust flow is restricted, and the intake system is compromised for noise and packaging constraints. These are exactly the areas where economical modifications can make a difference. The FA20 responds well to improved breathing, optimized fuel and ignition timing, and reduced rotational mass. With the right parts, you can realistically add 20 to 30 wheel horsepower without forced induction—enough to transform the car's demeanor while retaining daily-driver reliability.

Top Cost-Effective Modifications

1. Cold Air Intake

Swapping the stock air box for a cold air intake is one of the quickest ways to let your FR-S breathe. The factory intake is restrictive and draws air from inside the engine bay, which gets heat-soaked quickly. A well-designed cold air intake routes the air filter into a cooler area—typically behind the bumper or inner fender—and uses a smoother, larger-diameter pipe. This reduces intake restriction and lowers intake air temperature.

  • Expected gains: 5–10 horsepower, 4–6 lb-ft of torque, and a more responsive throttle.
  • Popular brands: Injen, K&N, Perrin, and AEM.
  • Installation difficulty: Easy (1–2 hours with basic hand tools).
  • Cost: $200–$400.

One caveat: some intakes require an ECU tune to avoid a lean condition at high RPM, so consider pairing this mod with a tune for maximum safety and performance.

2. Cat-Back Exhaust System

Behind the catalytic converter, the stock exhaust system is heavy and pinched. A cat-back replacement uses larger-diameter tubing, smoother mandrel bends, and less restrictive mufflers to reduce backpressure. This helps the engine exhale more freely, which can improve top-end power and throttle response. It also sheds a surprising amount of weight—stock exhaust components can weigh over 40 pounds; a stainless steel cat-back often weighs 20–25 pounds.

  • Expected gains: 5–10 horsepower, with most gains above 4,000 RPM.
  • Popular brands: Perrin, Borla, Invidia, and GReddy.
  • Installation difficulty: Moderate (requires jack and stands, a few hours).
  • Cost: $400–$900.

Cat-backs are often the first exhaust mod because they are legal in most states and do not require a tune. Pairing one with a cold air intake and a tune creates a solid foundation for further upgrades.

3. ECU Tune

Tuning the engine control unit (ECU) is the single most effective power modification for a naturally aspirated FR-S. The factory calibration leans toward emissions and fuel economy, leaving power on the table. A proper tune optimizes ignition timing, air-fuel ratios, and throttle mapping to match your specific modifications. Off-the-shelf (OTS) tunes are available from platforms like OpenFlash Tablet (OFT) and Ecutek, while custom dyno tuning provides even more precise gains.

  • Expected gains: 15–25 horsepower and 10–15 lb-ft of torque on a stock car; even more when combined with intake and exhaust work.
  • Popular platforms: OpenFlash Tablet (best value), Ecutek, and Delicious Tuning.
  • Installation difficulty: Easy to moderate (flashing via OBD2 port).
  • Cost: $500–$700 for an OTS tune with a tablet; $800–$1,200 for a custom dyno tune.

An ECU tune also eliminates the dreaded torque dip that plagues the FA20 between 3,500 and 4,500 RPM, dramatically improving driveability. Many tuners offer files specifically for 91 or 93 octane fuel, so you won't need to buy race gas.

4. Lightweight Flywheel

The stock flywheel weighs roughly 22 pounds. Replacing it with an aftermarket unit that weighs 10–13 pounds reduces the rotational inertia, allowing the engine to rev up faster and fall back quicker during shifts. This makes the car feel more eager and responsive, especially when paired with a lightweight driveshaft or lighter wheels. The effect is similar to a small weight reduction—the car accelerates more freely without actually increasing peak power.

  • Expected gains: Improved throttle response and 0.2–0.4 second faster in 0-60 mph times.
  • Popular brands: ACT, Fidanza, and Clutch Masters.
  • Installation difficulty: High (requires transmission removal).
  • Cost: $250–$400.

Because installation is labor-intensive, it's often done alongside a clutch replacement. If you plan to upgrade your clutch in the future, bundle it with the flywheel to save on labor costs.

5. Performance Tires

Power means nothing if you can't put it to the ground. The stock Primacy tires that came on many FR-S models are designed for low rolling resistance and long tread life—not grip. Upgrading to a set of ultra-high-performance summer tires transforms cornering ability and allows you to use the full potential of any engine mods. Better grip also reduces wheelspin, improving acceleration times.

  • Expected gains: Noticeably higher lateral grip (often 0.05–0.10 g), shorter braking distances, and faster lap times.
  • Popular tires: Michelin Pilot Sport 4S, Bridgestone Potenza RE-71R, Continental ExtremeContact Sport.
  • Cost: $600–$1,000 for a set of four (depending on size).

While tires don't add horsepower, they make every other mod more effective. They are arguably the best performance investment for your FR-S, and they wear out—so you'll need to replace them eventually anyway.

6. Lightweight Wheels

Reducing unsprung weight pays dividends in ride quality, handling, and acceleration. The factory 17-inch wheels weigh around 18–19 pounds each. A set of forged or flow-formed wheels can drop that by 4–6 pounds per corner. Less rotating mass means the engine doesn't have to work as hard to spin the wheels, and suspension components can react faster to road imperfections.

  • Expected gains: Quicker turn-in, more nimble feel, and marginal acceleration improvement.
  • Popular brands: Enkei (RPF1, NT03+M), RAYS (Gram Lights), OZ Racing.
  • Cost: $600–$1,200 per set.

Combined with performance tires, lightweight wheels are one of the most satisfying upgrades you can make—you'll feel the difference immediately on your first drive.

7. Header (UEL or EL)

Upgrading the exhaust manifold is a more involved but highly effective mod. The factory header is cast iron, restrictive, and uses equal-length (EL) runners that help with emissions but produce a flat, generic sound. Swapping to an aftermarket header—especially one with unequal-length (UEL) runners—can significantly free up power, raise the torque dip, and give the flat-four engine the iconic Subaru rumble.

  • Expected gains: 10–15 horsepower and 8–12 lb-ft of torque with a tune; also improves exhaust note.
  • Popular brands: Perrin (UEL), Tomei (UEL), JDL Auto Design (EL or UEL).
  • Installation difficulty: Moderate to high (requires removal of stock header and possible heat shielding).
  • Cost: $400–$800.

Note: A header replacement almost always requires an ECU tune to maintain proper air-fuel ratios. It also may not pass emissions testing in some states unless paired with a high-flow catalytic converter. Check your local regulations before ordering.

What Order Should You Mod Your FR-S?

A smart build sequence helps you avoid wasted money and duplicating labor. Here is a recommended order based on cost, ease of installation, and synergy between parts:

  1. Start with tires and lightweight wheels. These improve everything else and don't require a tune or special tools.
  2. Add an ECU tune. Even on a stock car, a tune wakes up the engine and removes the torque dip.
  3. Install a cold air intake and cat-back exhaust. These breathing mods work best when the tune is already optimized for them.
  4. Add a header. After you have intake, exhaust, and a tune dialed in, the header unlocks the biggest remaining chunk of power.
  5. Lightweight flywheel and clutch. Do this when your clutch wears out or when you need to pull the transmission for other work.
  6. Consider a lightweight driveshaft and rear differential bushings to further reduce drivetrain inertia (advanced, but relatively cheap).

This sequence ensures you don't buy parts that conflict with each other and that you aren't taking the transmission out just for a flywheel when you could have bundled it with a clutch replacement.

Considerations Before You Start

Modifying your FR-S is rewarding, but it's not without risks. Before spending money, think through these factors:

  • Warranty implications: Tuning and aftermarket parts can void portions of your powertrain warranty. Check with your dealer or keep stock parts to swap back if needed.
  • Emissions regulations: Most cat-back exhausts are legal, but headers and tuned ECUs may not pass visual inspections in California or other strict states. Know your local laws.
  • Insurance: Modifications can increase your premium. Some insurers offer coverage for aftermarket parts; disclose what you've done.
  • Maintenance: Tuned cars often require more frequent spark plug changes, and lightened flywheels can produce gear rattle at idle. Accept these trade-offs.

Real-World Results: A Sample Budget Build

Imagine you have a $3,000 budget. Here's what you could achieve:

  • Used or new ultra-high-performance tires ($700)
  • OpenFlash Tablet tune ($650)
  • Perrin cold air intake ($350)
  • Invidia N1 cat-back exhaust ($600)
  • JDL UEL header ($700)

Total: roughly $3,000 (plus installation if not DIY). With this setup, many owners report peak wheel horsepower around 190–200 whp (up from ~170 whp stock) and a broad, flat torque curve that eliminates the dreaded dip. The car revs freely, sounds aggressive, and handles significantly better thanks to the tires. That's a transformative change for the cost of a used set of wheels and a tune.

Conclusion

The Scion FR-S is a platform that rewards thoughtful, budget-conscious modification. You don't need forced induction or exotic parts to enjoy a meaningful increase in performance. Start with an ECU tune and good tires—those two alone will change how the car feels. From there, let your wallet and your driving goals guide you through intake, exhaust, and weight-reduction upgrades. The key is to research each part carefully, understand how it interacts with others, and prioritize quality over flash. Done right, your FR-S will become a sharper, faster, and more engaging machine without ever requiring a second mortgage.

For further reading, check out the FT86 Club Forum for build threads, FT86 Speedfactory for parts bundles, and ECUTEK's BRZ/FR-S page for tuning details.