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Subaru FA24D specs: 2.4L (145.7 ci) 4-cylinder, 94 x 86 mm (3.7008 x 3.3858 in) bore and stroke, 12.5:1 compression. Rated 228 hp. Rod ratio and piston speed.
The Subaru FA24D is oversquare — the 3.7008" bore exceeds the 3.3858" stroke by 9.3% — a layout that favors airflow and RPM over leverage at the crank. 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 36.4 ci (597 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, sitting between the 121.9 ci and 146.5 ci members. 2 factory variants share these dimensions, rated at 228 hp. Factory fitments include the Subaru BRZ, Toyota GR86.
| Displacement | 145.7 ci / 2.4 L |
|---|---|
| Bore | 3.7008" |
| Stroke | 3.3858" |
| Cylinders | 4 |
| Compression ratio | 12.5:1 |
| Bore/stroke ratio | 1.093 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 228 hp |
| Bore/stroke character | 1.093 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,386 ft/min — conservative for a street engine |
| Displacement per cylinder | 36.4 ci |
| Static compression | 12.5:1 — high enough that pump premium or better is normally required |
Each link opens the calculator with this engine's specs already filled in.
These records share identical bore, stroke, displacement and compression. They differ by model year and factory power rating.
| Year | Advertised HP | Code |
|---|---|---|
| — | 228 hp | FA24D |
| — | 228 hp | FA24D (NA), FA24D |