Unlock the Full Potential of Your Scion FR-S: A Roadmap to 50+ Horsepower

The Scion FR-S, along with its Subaru BRZ and Toyota GT86 siblings, has long been celebrated as a driver's car for the purist. Its low center of gravity, near-perfect 50:50 weight distribution, and responsive naturally aspirated engine make it a joy on winding roads. However, the 2.0-liter FA20 boxer engine, while eager, leaves many enthusiasts wanting more punch — particularly in the mid-range and top end. The good news is that the aftermarket ecosystem for this platform is mature, and with a carefully selected set of modifications, adding over 50 wheel horsepower is not only possible but a well-trodden path. This guide breaks down the top five power upgrades that deliver measurable, real-world gains, providing you with the knowledge to build a faster, more responsive car without sacrificing reliability.

1. High-Flow Cold Air Intake System

The factory air intake system on the FR-S is a compromise between cost, noise, and filtration. It draws air from a relatively restricted area and uses a convoluted path that creates turbulence. Replacing it with a properly designed cold air intake (CAI) is often the first step many owners take, and for good reason.

How It Works

A high-flow intake replaces the restrictive factory airbox and intake tubing with a larger-diameter, smoother pipe and a high-flow, pleated cotton or dry filter. The key advantage is a reduction in intake restriction, which allows the engine to inhale more easily. This reduces the parasitic loss associated with drawing air through a narrow passage, freeing up a modest but noticeable amount of power — typically in the 8 to 12 horsepower range at the wheels on a stock engine.

Choosing the Right System

Not all intakes are created equal. The most effective designs for the FA20 engine are those that shield the filter from under-hood heat or relocate it into the front bumper area where it can access cooler, denser air. Cooler air contains more oxygen molecules, which is critical for combustion. A heat-soaked intake that pulls in hot air from the engine bay can actually reduce performance, negating any gains from reduced restriction. Look for kits that include a sealed heat shield or a dedicated cold-air box. Intakes from established manufacturers such as Perrin and Grimmspeed have proven records on this platform.

Installation and Tuning Considerations

Installation is straightforward for a DIY mechanic, usually taking one to two hours with basic hand tools. While a standalone intake can provide a small gain on an otherwise stock car, the real benefit comes when it is paired with a tune. The engine's ECU will adapt within limits to the increased airflow, but a custom or off-the-shelf tune can optimize the fuel and ignition timing to fully capitalize on the extra air, often adding an additional 5 horsepower on top of the intake's baseline gain.

2. Free-Flowing Cat-Back or Axle-Back Exhaust System

The stock exhaust system on the FR-S is notably quiet and restrictive, using multiple resonators and a baffled muffler to meet noise regulations. Swapping out the rear section — either the axle-back or the full cat-back system — is a popular upgrade that addresses both performance and sound.

Mechanism of Gain

The primary purpose of an upgraded exhaust is to reduce backpressure, allowing exhaust gases to exit the cylinders more freely. This reduces the work the engine has to do during the exhaust stroke, effectively freeing up horsepower. For the FA20 engine, a high-quality cat-back exhaust typically yields 5 to 10 wheel horsepower. While this may sound modest, the improvement in throttle response and the reduction in engine strain are very noticeable.

System Types and Trade-Offs

  • Axle-Back: Replaces only the muffler and tips. Lighter and cheaper, but offers smaller performance gains (3-5 hp). Primarily a sound and weight-saving mod.
  • Cat-Back: Replaces everything from the catalytic converter back. Provides better flow and more significant power gains. Also allows for larger diameter piping (2.5 to 3 inches).
  • Material: Stainless steel is durable and common. Titanium or Inconel options save weight but are significantly more expensive.

Sound and Daily Driving

Be aware that a cat-back exhaust on the FA20 can be loud. The boxer engine has a distinctive, throaty rumble, and an aftermarket exhaust amplifies this. If you daily drive your FR-S, consider a system with a Helmholtz resonator or a larger muffler to keep drone on the highway at bay. Brands like Injen Technology offer systems that balance flow with livability. Remember, this upgrade works best in concert with other breathing mods and a tune.

3. Performance Headers (Equal or Unequal Length)

Arguably one of the most impactful single modifications for the FA20 engine is the installation of aftermarket performance headers (also known as exhaust manifolds). The stock header is a cast-iron or tubular piece with restrictive, small-diameter primaries that choke the engine at high RPM.

The Science of Exhaust Scavenging

Headers are designed with smooth, mandrel-bent tubing that merges into a collector. This design promotes exhaust scavenging — the pressure wave from one exhaust pulse helps pull the next pulse out of the cylinder. Reducing backpressure at the header level is much more effective than doing so further downstream because it directly affects cylinder evacuation during the valve overlap period. A set of quality 4-2-1 or 4-1 headers can add between 10 and 15 wheel horsepower on an otherwise stock car, with most of the gain coming in the mid-to-upper RPM range.

Unequal Length vs. Equal Length

  • Unequal Length (UEL): Gives the classic Subaru boxer rumble but can slightly reduce top-end power due to uneven scavenging. They also take longer to warm up the catalytic converter.
  • Equal Length (EL): Smoother exhaust note, better high-RPM power and torque, and faster catalyst light-off. They are generally preferred for maximum horsepower builds.

Installation and Platform-Specific Tips

Header installation on the FR-S is a more involved job, requiring you to support the engine and remove the original header from below. The bolts on the FA20 are prone to seizing, so penetrating oil and heat are often needed. A tune is highly recommended after installing headers, as the change in exhaust flow can cause the engine to run lean in certain areas. A proper tune will not only add more power but also ensure safe air-fuel ratios.

4. ECU Flash Tune (ECU Tune or Reflash)

All the breathing modifications in the world will only get you so far without addressing the engine's brain. The factory ECU calibration is conservative, prioritizing emissions, fuel economy, and engine safety margins over peak power. An ECU flash tune rewrites the parameters inside the engine control unit to optimize performance for your specific modifications and fuel quality.

What a Tune Changes

  • Ignition Timing: Advances timing to extract more energy from combustion, increasing torque and horsepower.
  • Air-Fuel Ratio (AFR): Targets a stoichiometric or slightly richer mixture for maximum power under wide-open throttle, while maintaining safe lambda at cruise.
  • Throttle Mapping: Eliminates the factory throttle lag, making the car feel much more responsive to pedal inputs.
  • Rev Limit: Can be raised (cautiously) to allow the engine to pull past the factory 7,400 rpm redline, often adding a few more horsepower at the top.

Standalone vs. Open Source vs. Off-the-Shelf

For most owners building toward the 50+ horsepower goal, an open-source tune using software like RomRaider or ECUtek is the best balance of cost and capability. A remote e-tune from a reputable shop (such as those specializing in the FA20 platform) can yield excellent results. An off-the-shelf tune, while convenient, is a compromise — a custom tune tailored to your exact combination of intake, headers, and exhaust will always produce more power and be safer. A good tune alone on a car with bolt-ons can add 15 to 25 wheel horsepower on top of the hardware gains.

5. Forced Induction: The Turbocharger Kit (The Big Leap)

If your goal is a reliable, streetable 50 to 100+ horsepower increase, nothing compares to adding a turbocharger kit. While the first four mods (intake, exhaust, headers, tune) can collectively net you 35 to 45 wheel horsepower on a good day, a turbo kit is the only way to guarantee a 50+ horsepower jump with room to grow.

How It Delivers Power

A turbocharger uses exhaust gas energy to spin a turbine, which in turn compresses the intake air. This forces significantly more air (and fuel) into the cylinders than atmospheric pressure alone can provide. For the FA20 engine, a modest 5 to 7 psi of boost from a well-designed kit can transform the car. A typical Stage 1 or Stage 2 turbo kit for the FR-S will produce between 250 and 300 wheel horsepower — a gain of 80 to 130 horsepower over a stock car.

Kit Considerations

  • Turbo Size: A small-to-mid frame turbo (e.g., GTX2860R, Garrett G25-550) is ideal for fast spool and strong mid-range torque. Large turbos sacrifice response for peak power.
  • Intercooling: Essential for reducing intake air temperatures under boost. Air-to-air intercoolers are common and effective for moderate power levels.
  • Fuel System: Standard injectors and fuel pump can handle modest boost. Over 300 hp, you will need upgraded injectors and a higher-flow fuel pump.
  • Oil Management: The FA20 is known for oil starvation issues under high lateral load. A turbo kit necessitates an oil cooler and possibly an oil pan baffle or accusump.

Reliability and Cost

A turbo kit is a significant investment — typically $4,000 to $7,000 for a complete kit, plus installation and tuning. However, when properly installed and tuned on a healthy engine, a turbocharged FR-S can be as reliable as a stock car. The key is not to chase peak numbers but to build a conservative tune with a safe margin for fuel quality and heat. Kits from Full Blown Motorsports and P&L Motorsports have proven track records on the FA24/FA20 platforms.

Putting It All Together: The 50+ Horsepower Recipe

Achieving a genuine, repeatable 50+ wheel horsepower gain requires a synergistic combination of mods, not just a single part. Here is a proven, step-by-step recipe:

  1. Stage 1 (Bolt-Ons + Tune): Start with a cold air intake, cat-back exhaust, and performance headers. Have the car custom tuned on 93 octane or E85 (if available). This package typically yields 35 to 45 wheel horsepower over stock, depending on the tune.
  2. Stage 2 (Forced Induction): If you want to cross the 50-horsepower threshold with certainty, add a turbo kit. A conservative 5-6 psi tune with the bolt-ons above will comfortably produce 60 to 80 wheel horsepower over stock, hitting your target with authority.
  3. Supporting Mods: Any power increase generates more heat. Add a high-capacity oil cooler, a larger radiator (if tracking), and consider a lightweight flywheel for quicker throttle response.

Final Considerations

Reaching 50+ horsepower in your Scion FR-S is an achievable goal that transforms the driving experience without ruining the car's famed balance. The key is to prioritize quality parts, proper installation, and a professional tune. Avoid cheap knockoff parts that compromise reliability — the FA20 engine is robust but unforgiving of poor tuning or insufficient fueling. Invest in a good dyno or data-logging session to ensure your engine is happy at wide-open throttle. With the right combination of air, exhaust, management, and maybe a little boost, your FR-S will go from a fun momentum car to a genuinely fast sports car that can hang with much more expensive machinery.