See other engines in this family
Subaru EA-81 specs: 1.8L (110 ci) 4-cylinder, 92 x 67 mm (3.6220 x 2.6378 in) bore and stroke, 8.7:1 compression. Rated 73 hp, 1981–1987.
The Subaru EA-81 is oversquare — the 3.622" bore exceeds the 2.6378" stroke by 37.3% — a layout that favors airflow and RPM over leverage at the crank. The 2.6378" stroke does not reach 4,000 ft/min of mean piston speed until about 9,100 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 4 cylinders displaces 27.5 ci (451 cc).
8.7:1 on aluminum heads is low by modern standards and generally happy on regular pump fuel.
It is one of 11 engines in the EA family, the largest at 110 ci. 7 factory variants share these dimensions, rated at 73 hp across 1981–1987.
| Displacement | 110 ci / 1.8 L |
|---|---|
| Bore | 3.622" |
| Stroke | 2.6378" |
| Cylinders | 4 |
| Compression ratio | 8.7:1 * |
| Bore/stroke ratio | 1.373 |
* Compression ratio from a single source; not yet cross-verified.
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | SOHC |
| Fuel type | gas |
| Advertised HP | 73 hp |
| Years | 1981–1987 |
| Bore/stroke character | 1.373 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 2,638 ft/min — conservative for a street engine |
| Displacement per cylinder | 27.5 ci |
| Static compression | 8.7:1 — 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 |
|---|---|---|
| 1981 | 73 hp | EA-81 |
| 1982 | 73 hp | EA-81 |
| 1983 | 73 hp | EA-81 |
| 1984 | 73 hp | EA-81 |
| 1985 | 73 hp | EA-81 |
| 1986 | 73 hp | EA-81 |
| 1987 | 73 hp | EA-81 |
1 factory vehicle, 1981–1987. Each year opens that model's engine table.