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Porsche M44/40 specs: 2.5L (151 ci) 4-cylinder, 100 x 78.9 mm (3.9370 x 3.1063 in) bore and stroke, 10.9:1 compression. Built 1987–1988.
The Porsche M44/40 is oversquare — the 3.937" bore exceeds the 3.1063" stroke by 26.7% — a layout that favors airflow and RPM over leverage at the crank. The 3.1063" stroke does not reach 4,000 ft/min of mean piston speed until about 7,750 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 4 cylinders displaces 37.8 ci (619 cc).
10.9:1 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 5 engines in the 944 family, all of them 151 ci — the differences between them are in compression, heads and rating, not displacement. 2 factory variants share these dimensions across 1987–1988.
| Displacement | 151 ci / 2.5 L |
|---|---|
| Bore | 3.937" |
| Stroke | 3.1063" |
| Cylinders | 4 |
| Configuration | I4 |
| Compression ratio | 10.9:1 |
| Bore/stroke ratio | 1.267 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | SOHC |
| Fuel type | gas |
| Years | 1987–1988 |
| Bore/stroke character | 1.267 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,106 ft/min — conservative for a street engine |
| Displacement per cylinder | 37.8 ci |
| Static compression | 10.9:1 — 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 |
|---|---|---|
| 1987 | — | M44/40 |
| 1988 | — | M44/40 |
2 factory vehicles, 1983–1989. Each year opens that model's engine table.