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Porsche MA1/01 specs: 3.8L (231.9 ci) 6-cylinder, 102 x 77.5 mm (4.0157 x 3.0512 in) bore and stroke, 12.5:1 compression. Rated 385 hp. DOHC.
The Porsche MA1/01 is oversquare — the 4.0157" bore exceeds the 3.0512" stroke by 31.6% — a layout that favors airflow and RPM over leverage at the crank. The 3.0512" stroke does not reach 4,000 ft/min of mean piston speed until about 7,850 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 6 cylinders displaces 38.7 ci (633 cc).
12.5:1 on aluminum heads is high for a production gasoline engine; running a ratio like that on pump fuel depends on chamber design and fuel delivery rather than the number alone.
It is one of 3 engines in the MA1 family, all of them 231.9 ci — the differences between them are in compression, heads and rating, not displacement. Factory fitments include the 911 Carrera S (997.2).
| Displacement | 231.9 ci / 3.8 L |
|---|---|
| Bore | 4.0157" |
| Stroke | 3.0512" |
| Cylinders | 6 |
| Compression ratio | 12.5:1 |
| Bore/stroke ratio | 1.316 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 385 hp |
| Bore/stroke character | 1.316 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,051 ft/min — conservative for a street engine |
| Displacement per cylinder | 38.6 ci |
| Static compression | 12.5:1 — high enough that pump premium or better is normally required |
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