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Subaru EJ255 specs: 2.5L (150.2 ci) 4-cylinder, 99.5 x 79 mm (3.9173 x 3.1102 in) bore and stroke. Rated 224-265 hp, 2006–2014. Used in the Subaru WRX. DOHC.
The Subaru EJ255 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 37.6 ci (615 cc).
It is one of 37 engines in the EJ family, sitting between the 91.1 ci and 152 ci members. 9 factory variants share these dimensions, rated from 224 to 265 hp across 2006–2014.
| Displacement | 150.2 ci / 2.5 L |
|---|---|
| Bore | 3.9173" |
| Stroke | 3.1102" |
| Cylinders | 4 |
| Bore/stroke ratio | 1.26 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 224–265 hp |
| Years | 2006–2014 |
| 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 |
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 |
|---|---|---|
| 2006 | 230 hp | EJ255 |
| 2007 | 230 hp | EJ255 |
| 2008 | 224 hp | EJ255 |
| 2009 | 265 hp | EJ255 |
| 2010 | 265 hp | EJ255 |
| 2011 | 265 hp | EJ255 |
| 2012 | 265 hp | EJ255 |
| 2013 | 265 hp | EJ255 |
| 2014 | 265 hp | EJ255 |