The Real-World Impact of Upgrading Your FA20 to 330 Horsepower

The Subaru FA20 engine has earned a loyal following for its smooth power delivery, lightweight construction, and impressive fuel efficiency in stock form. Found in the Subaru BRZ, Toyota 86, and Scion FR-S, this 2.0-liter flat-four engine offers a balanced platform that many enthusiasts choose to modify. Pushing the FA20 to 330 wheel horsepower represents a significant performance leap—roughly doubling the factory output. While the thrill of extra power is undeniable, the real-world trade-offs in fuel economy and long-term reliability are often misunderstood. This article provides a detailed, data-driven look at what happens when you take the FA20 from 200 hp to 330 hp, covering daily driving fuel consumption, common reliability pitfalls, and the build choices that separate a durable 330 hp setup from a ticking time bomb.

Understanding the FA20 Engine’s Stock Capabilities

Before exploring the upgrade path, it is important to appreciate the FA20’s design. It is a naturally aspirated, horizontally opposed four-cylinder engine with a high compression ratio of 12.5:1. Subaru engineered it for a broad power band and excellent thermal efficiency. In stock form, the FA20 produces about 200-205 horsepower at the crank and achieves 25-30 mpg on the highway under normal driving conditions. The engine features a D-4S dual injection system (port and direct injection) that helps reduce carbon buildup and optimizes combustion at low and high loads.

To reach 330 wheel horsepower—which equates to roughly 370-380 at the crank—the engine requires forced induction. A turbocharger or supercharger kit is almost mandatory, along with supporting modifications such as upgraded fuel injectors, a high-flow fuel pump, intercooler, and a custom engine tune. The factory internals (pistons, rods, bearings) were not designed for sustained 330 hp operation, so reliability becomes a central concern. This section sets the stage for understanding how each modification affects both fuel economy and engine longevity.

Fuel Economy After the Upgrade: Real-World Numbers

The most common question from owners considering a 330 hp FA20 is: “How much will my gas mileage drop?” The answer depends heavily on driving style, tune quality, and supporting modifications. However, real-world reports from forums and independent testers provide a reliable baseline.

City and Highway Fuel Economy Breakdown

  • Stock FA20: 21-24 mpg city, 28-32 mpg highway (EPA combined ~25 mpg).
  • 330 hp turbocharged FA20: 16-19 mpg city, 22-26 mpg highway (combined ~19-21 mpg).

The drop is most pronounced in stop-and-go city driving, where the turbo spools frequently and extra fuel is injected to keep the air-fuel ratio safe. On the highway, the difference narrows because the engine operates at low boost (or vacuum) when cruising. A well-tuned setup can maintain 25+ mpg on the highway if the driver keeps the boost gauge low and uses light throttle. Aggressive acceleration and sustained high-speed driving easily push fuel consumption into the 15-18 mpg range.

Factors That Influence Fuel Economy in a 330 hp FA20

  • Boost Pressure and Tune: A conservative tune that targets lower boost (around 8-10 psi) will return better fuel economy than a max-effort 14-16 psi tune. The air-fuel ratio and ignition timing are critical; a too-rich mixture wastes fuel without adding power.
  • Driving Habits: Enthusiasts who use boost frequently will see fuel economy below 20 mpg. Those who drive moderately can often keep highway mileage close to stock levels.
  • Vehicle Weight and Gearing: Heavier wheels, sticky tires, and aftermarket aerodynamic parts (like large wings) increase drag and rolling resistance, reducing efficiency.
  • Fuel Quality: Running 93 octane (or E85) is necessary for safe high-power operation. E85 typically reduces fuel economy by 20-30% compared to gasoline due to its lower energy density.

It is also worth noting that many tuners offer a “eco map” or low-boost tune for daily driving, allowing the driver to switch between a performance map and a fuel-saver map. This can mitigate the fuel economy penalty significantly.

Reliability After Upgrading to 330 hp: What to Expect

Reliability is the second pillar of the real-world experience. The FA20’s factory internals are adequate for its stock output, but 330 hp represents a 65% increase over stock. The engine’s weak points become exposed under sustained high load and high RPM. Below are the most common reliability concerns and how to address them.

Critical Weak Points of the FA20 at 330 hp

  • Connecting Rods: The stock rods are thin and prone to bending under high torque, especially if the tune is aggressive and the engine sees knock events. Upgraded forged rods are highly recommended for any 330 hp build.
  • Pistons: The factory hypereutectic pistons can crack under detonation. Forged pistons with a lower compression ratio (9.5:1 to 10.5:1) are a common upgrade to reduce knock risk and allow safer boost levels.
  • Oil System: The FA20 has a low oil capacity and a reputation for oil starvation during high-g cornering. A baffled oil pan, oil cooler, and possibly an Accusump or dry sump system are necessary for track use.
  • Cooling System: With double the heat output, the stock radiator and coolant system may struggle, especially in hot climates or on the track. An upgraded radiator, oil cooler, and high-flow water pump are common upgrades.
  • Transmission and Drivetrain: The stock 5-speed or 6-speed manual transmission in the BRZ/86 can handle 330 hp with careful driving, but clutch slip becomes an issue. An upgraded clutch and lightweight flywheel are advisable. The rear differential is robust but may need cooling if the car is used for road racing.

Real-World Reliability Reports from Owners

Data from FA20 owner communities (such as FT86 Club, NASIOC, and dedicated Facebook groups) indicates that reliability varies widely based on build quality and maintenance. A well-built, conservatively tuned 330 hp FA20 with forged internals can last 40,000-60,000 miles of mixed driving without major issues. However, many owners report failures before 20,000 miles when using stock internals and aggressive tunes. Common failure points include:

  • Rod bearing failure due to oil starvation or detonation.
  • Ringland failure (cracked piston ring lands) from excessive boost or lean conditions.
  • Head gasket failure when coolant temperatures spike.

To maximize reliability, professionals recommend a “full build” approach: forged rods and pistons, head studs, a high-flow oil pump, baffled oil pan, and a robust cooling system. The total cost of a reliable 330 hp build often exceeds $8,000-$12,000, including labor. Cutting corners on internals may save money upfront, but the risk of catastrophic engine failure increases dramatically.

Comparison to Other 330 hp Engine Platforms

It is helpful to benchmark the FA20 against other engines built for similar power levels. The 2JZ-GE (Toyota), LS3 (GM), and EJ25 (Subaru) all have proven reliability records at 330 hp, but each has its own trade-offs. The FA20 is lighter and more efficient at lower speeds, but its smaller displacement forces it to work harder to produce the same power, leading to higher thermal stress. The LS3, for example, achieves 400+ hp with stock internals and better fuel economy at cruise than a 330 hp FA20. However, the FA20’s lower weight and superior handling potential make it a compelling choice for balanced performance.

External reading: For a deeper dive into FA20 internal upgrades, check out FT86 Club forums and Tuning Tech FS’s FA20 build guide.

Practical Tips for Daily Driving a 330 hp FA20

Owning a 330 hp FA20 car is not just about the numbers—it is about the daily experience. Here are actionable recommendations from experienced owners and tuners to keep the car reliable and fuel-efficient:

  • Use a multi-tune switch: Have a conservative daily map (maybe 280-300 hp) and a separate track map. This preserves fuel economy and engine life during commutes.
  • Monitor oil temperature and pressure: Invest in a quality gauge or digital display. Keep oil temp below 230°F for sustained driving.
  • Change oil every 3,000-4,000 miles: High-horsepower engines shear oil faster. Use a high-quality synthetic like Motul 300V or Red Line 5W-30.
  • Let the engine warm up properly: Allow oil to reach at least 160°F before heavy throttle. Cold oil does not lubricate turbo bearings well.
  • Avoid short trips: The engine needs to reach full operating temperature to burn off moisture and prevent fuel dilution.
  • Check fuel trims regularly: A wideband O2 sensor (e.g., AEM) helps detect lean conditions before damage occurs.

Long-Term Ownership Cost and Maintenance

Beyond fuel and wear, a 330 hp FA20 incurs higher maintenance costs. Upgraded brakes, suspension components, and tires are necessary to handle the extra power safely. Budget for an extra $500-$1,000 per year in consumables (tires, pads, fluids) compared to a stock car. The forced induction system itself requires periodic checks: turbo seals, intercooler boots, and belt tension. Many owners plan for a mid-life engine rebuild around 80,000-100,000 miles for peace of mind.

For external reliability data, refer to the Subaru owner resources and the EngineDIY FA20 reliability overview.

Final Verdict: Is the Upgrade Worth It?

Upgrading a FA20 to 330 hp transforms the car into a genuinely quick machine, capable of hanging with many modern sports cars. The fuel economy penalty is modest (3-5 mpg average loss) if driven sensibly, and reliability can be excellent with a properly built engine and meticulous maintenance. The key is to build for reliability first: use forged internals, a high-quality turbo kit (e.g., from Blouch Turbo or GrimmSpeed), and invest in a professional tune from a respected shop.

Enthusiasts who skip the forged rods and pistons may save money initially, but they face a high probability of engine failure within 10,000-20,000 miles. Those who do the job right will enjoy a reliable, fuel-efficient daily driver that also delivers spine-tingling performance when the road opens up.

In short: 330 hp is the sweet spot for the FA20—enough power to be thrilling without overwhelming the chassis—but it demands respect, careful maintenance, and a solid budget. Treat it right, and it will reward you with thousands of miles of driving enjoyment.