Definition
The Subaru FA engine is a family of horizontally opposed (boxer) four-cylinder gasoline internal‑combustion engines produced by Subaru Corporation (formerly Fuji Heavy Industries) for use in a range of Subaru passenger vehicles.
Overview
Introduced in 2012, the FA series succeeded the earlier EJ engine family and incorporates Subaru’s “Subaru Global Platform” design principles. The FA engines are employed in models such as the Subaru Impreza, Legacy, Outback, and Crosstrek, primarily in markets where emissions standards and fuel‑efficiency requirements demand modern engine technology. The series includes a variety of displacements, most commonly the 2.0 L FA20 and the 2.5 L FA25, with both naturally aspirated and turbocharged variants (e.g., the FA20F turbocharged engine used in the WRX and WRX STI models).
Etymology/Origin
The designation “FA” follows Subaru’s internal naming convention for engine families. The initial “F” denotes the engine’s placement within the “F” series of Subaru’s horizontally opposed designs, while the subsequent letter differentiates the specific generation or architecture; “A” indicates the first major redesign after the EJ series. The naming does not have a publicly documented linguistic origin beyond this internal coding system.
Characteristics
| Feature | Details |
|---|---|
| Configuration | Horizontally opposed (boxer) four‑cylinder |
| Valvetrain | DOHC with Variable Valve Timing (VVT) on both intake and exhaust camshafts |
| Construction | Aluminum alloy block and cylinder heads, with a forged‑steel crankshaft |
| Bore × Stroke | FA20: 86 mm × 86 mm (square); FA25: 92 mm × 92 mm (square) |
| Displacement | FA20: 1,998 cc; FA25: 2,494 cc |
| Compression Ratio | Naturally aspirated: 10.5:1 (FA20) to 10.8:1 (FA25); Turbocharged FA20F: 10.0:1 |
| Induction | Naturally aspirated or twin‑scroll turbocharger with intercooler (FA20F) |
| Fuel System | Direct injection (D-4S) combining gasoline direct injection and multi‑point port injection |
| Power Output | FA20 (NA): 150–155 hp (112–115 kW); FA25 (NA): 182–200 hp (136–149 kW); FA20F (turbo): 268–310 hp (200–231 kW) depending on model year and market |
| Torque | FA20 (NA): 140 Nm; FA25 (NA): 238 Nm; FA20F (turbo): 350 Nm (258 lb‑ft) |
| Emissions | Meets Euro 6, U.S. EPA Tier 3, and equivalent Asian standards via variable valve timing, direct injection, and exhaust after‑treatment (catalytic converters, SCR in some markets) |
| Cooling | Water‑cooled with integrated oil cooler; turbocharged variants feature additional cooling circuits for the charge air cooler |
| Compatibility | Designed for Subaru’s symmetrical all‑wheel‑drive (AWD) layout, with equal‑length crankshaft throws to promote balanced engine dynamics |
Related Topics
- Subaru EJ engine family – Predecessor boxer engine series, produced from 1989 to 2012.
- Subaru Global Platform (SGP) – The vehicle architecture that incorporates the FA engine family.
- Subaru D-4S injection system – Dual injection technology used in FA engines for improved efficiency and power.
- Boxer engine – General term for horizontally opposed piston engines, of which the FA is a specific implementation.
- Turbocharging in automotive applications – Technology employed in the FA20F and related turbocharged variants.
- Subaru WRX and WRX STI – Performance models that have utilized the FA20F turbocharged engine.
Note: All specifications are based on manufacturer data and publicly released technical documentation up to the year 2025.