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Subaru EJ20 (NA SOHC) specs: 2.0L (122 ci) 4-cylinder, 92 x 75 mm (3.6220 x 2.9528 in) bore and stroke, 9.7:1 compression. Rated 125 hp. SOHC.
The Subaru EJ20 (NA SOHC) is oversquare — the 3.622" bore exceeds the 2.9528" stroke by 22.7% — a layout that favors airflow and RPM over leverage at the crank. The 2.9528" stroke does not reach 4,000 ft/min of mean piston speed until about 8,150 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 4 cylinders displaces 30.5 ci (500 cc).
9.7:1 on aluminum heads is in the range that usually runs on pump premium; aluminum sheds heat faster than iron, which makes the same number a little more forgiving.
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 at 125 hp. Factory fitments include the Subaru Legacy, Subaru Impreza, Subaru Forester.
| Displacement | 122 ci / 2 L |
|---|---|
| Bore | 3.622" |
| Stroke | 2.9528" |
| Cylinders | 4 |
| Compression ratio | 9.7:1 |
| Bore/stroke ratio | 1.227 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | SOHC |
| Fuel type | gas |
| Advertised HP | 125 hp |
| Bore/stroke character | 1.227 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 2,953 ft/min — conservative for a street engine |
| Displacement per cylinder | 30.5 ci |
| Static compression | 9.7:1 — in the range that usually runs on pump premium |
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 |
|---|---|---|
| — | 125 hp | EJ20 (NA SOHC) |
| — | 125 hp | EJ20E, EJ20 (NA SOHC) |