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Subaru EJ25D specs: 2.5L (150.2 ci) 4-cylinder, 99.5 x 79 mm (3.9173 x 3.1102 in) bore and stroke. Rated 155-165 hp, 1996–1999. Used in the Subaru Legacy.
The Subaru EJ25D 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. A rod ratio of 1.652 is in the range most production engines fall in. Each of the 4 cylinders displaces 37.6 ci (615 cc).
It is one of 43 engines in the EJ family, sitting between the 91.1 ci and 152 ci members. 4 factory variants share these dimensions, rated from 155 to 165 hp across 1996–1999.
| Displacement | 150.2 ci / 2.5 L |
|---|---|
| Bore | 3.9173" |
| Stroke | 3.1102" |
| Cylinders | 4 |
| Rod length | 5.138" |
| Rod ratio | 1.652 |
| Bore/stroke ratio | 1.26 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Firing order | 1-3-2-4 |
| Advertised HP | 155–165 hp |
| Years | 1996–1999 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. |
|---|---|---|---|---|
| 1998 | EJ25D net | 165 * | — | — |
Factory specification sheet. * Not yet cross-verified.
| 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 |
| Rod ratio | 1.652 — moderate — the range most production V8s fall in |
| 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 |
|---|---|---|
| 1996 | 155 hp | EJ25D |
| 1997 | 165 hp | EJ25D |
| 1998 | 165 hp | EJ25D |
| 1999 | 165 hp | EJ25D |
4 factory vehicles, 1996–1999. Each year opens that model's engine table.