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Porsche MA1 2.9 specs: 2.9L (176.5 ci) 6-cylinder, 89 x 77.5 mm (3.5039 x 3.0512 in) bore and stroke, 11.5:1 compression. Rod ratio and piston speed.
The Porsche MA1 2.9 is oversquare — the 3.5039" bore exceeds the 3.0512" stroke by 14.8% — 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 29.4 ci (482 cc).
11.5:1 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 14 engines in the MA1 family, sitting between the 165.1 ci and 231.9 ci members.
| Displacement | 176.5 ci / 2.9 L |
|---|---|
| Bore | 3.5039" |
| Stroke | 3.0512" |
| Cylinders | 6 |
| Compression ratio | 11.5:1 |
| Bore/stroke ratio | 1.148 |
| Fuel type | gas |
|---|
| Bore/stroke character | 1.148 — 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 | 29.4 ci |
| Static compression | 11.5:1 — high enough that pump premium or better is normally required |
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