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Subaru EJ257 specs: 2.457L (150 ci) 4-cylinder, 99.5 x 79 mm (3.9173 x 3.1102 in) bore and stroke, 8.2:1 compression. Rated 250-300 hp. DOHC.
The Subaru EJ257 is oversquare — the 3.9173" bore exceeds the 3.1102" stroke by 26.0% — a layout that favors airflow and RPM over leverage at the crank. The 3.1102" stroke does not reach 4,000 ft/min of mean piston speed until about 7,700 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 4 cylinders displaces 37.5 ci (615 cc).
8.2:1 on aluminum heads is low by modern standards and generally happy on regular pump fuel.
It is one of 37 engines in the EJ family, sitting between the 91.1 ci and 152 ci members. 2 factory variants share these dimensions, rated from 250 to 300 hp. Factory fitments include the Subaru Impreza WRX/STi, Subaru Forester XT, Subaru Legacy GT and 10 others.
| Displacement | 150 ci / 2.457 L |
|---|---|
| Bore | 3.9173" |
| Stroke | 3.1102" |
| Cylinders | 4 |
| Compression ratio | 8.2:1 |
| Bore/stroke ratio | 1.26 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 250–300 hp |
| Bore/stroke character | 1.260 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,110 ft/min — conservative for a street engine |
| Displacement per cylinder | 37.5 ci |
| Static compression | 8.2:1 — low by modern standards, generally happy on regular pump fuel |
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 |
|---|---|---|
| — | 250 hp | EJ255/257 (Turbo DOHC), EJ255, EJ257 (Turbo DOHC), EJ255/EJ257 (Turbo DOHC), EJ255 (Turbo DOHC), EJ257 |
| — | 300 hp | EJ257, EJ257 (Turbo DOHC STI), EJ257 (Turbo STI) |