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Subaru Fa20 D specs: 2.0L (121.9 ci) 4-cylinder, 86 x 86 mm (3.3858 x 3.3858 in) bore and stroke, 12.5:1 compression. Rated 200 hp. DOHC.
The Subaru Fa20 D is exactly square — 3.3858" bore and 3.3858" stroke are the same — which splits the difference between a high-revving layout and a torque layout. The 3.3858" stroke does not reach 4,000 ft/min of mean piston speed until about 7,100 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 4 cylinders displaces 30.5 ci (499 cc).
12.5:1 on aluminum heads is high for a production gasoline engine; running a ratio like that on pump fuel depends on chamber design and fuel delivery rather than the number alone.
It is one of 11 engines in the FA family, the smallest at 121.9 ci. Factory fitments include the Subaru BRZ, Toyota 86, Scion FR-S.
| Displacement | 121.9 ci / 2 L |
|---|---|
| Bore | 3.3858" |
| Stroke | 3.3858" |
| Cylinders | 4 |
| Compression ratio | 12.5:1 |
| Bore/stroke ratio | 1 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 200 hp |
| Bore/stroke character | 1.000 — square — bore and stroke are within 5%, a balanced compromise |
|---|---|
| Mean piston speed at 6,000 RPM | 3,386 ft/min — conservative for a street engine |
| Displacement per cylinder | 30.5 ci |
| Static compression | 12.5:1 — high enough that pump premium or better is normally required |
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