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Subaru EJ255 specs: 2.5L (153 ci) 4-cylinder, 99.5 x 79 mm (3.9173 x 3.1102 in) bore and stroke, 8.2:1 compression. Rated 210 hp, 2004–2006.
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 38.3 ci (627 cc).
8.2:1 is low by modern standards and generally happy on regular pump fuel.
It is one of 3 engines in the Subaru 153ci family, all of them 153 ci — the differences between them are in compression, heads and rating, not displacement. 3 factory variants share these dimensions, rated at 210 hp across 2004–2006.
| Displacement | 153 ci / 2.5 L |
|---|---|
| Bore | 3.9173" |
| Stroke | 3.1102" |
| Cylinders | 4 |
| Compression ratio | 8.2:1 |
| Bore/stroke ratio | 1.26 |
| Fuel type | gas |
|---|---|
| Firing order | 1-3-2-4 |
| Advertised HP | 210 hp |
| Years | 2004–2006 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. |
|---|---|---|---|---|
| 2004 | EJ255 net | 210 @ 5600 | 235 lb-ft @ 3600 | 8.2:1 |
| 2005 | EJ255 net | 210 @ 5600 | 235 lb-ft @ 3600 | 8.2:1 |
| 2006 | EJ255 net | 210 @ 5600 | 235 lb-ft @ 3600 | 8.2:1 |
Factory specification sheet.
| 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 | 38.3 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 |
|---|---|---|
| 2004 | 210 hp | EJ255 |
| 2005 | 210 hp | EJ255 |
| 2006 | 210 hp | EJ255 |
1 factory vehicle, 2004–2006. Each year opens that model's engine table.