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Porsche MA2 2.5 Turbo specs: 2.5L (152.4 ci) 4-cylinder, 102 x 76.4 mm (4.0157 x 3.0079 in) bore and stroke, 9.5:1 compression. Rod ratio and piston speed.
The Porsche MA2 2.5 Turbo is oversquare — the 4.0157" bore exceeds the 3.0079" stroke by 33.5% — a layout that favors airflow and RPM over leverage at the crank. The 3.0079" stroke does not reach 4,000 ft/min of mean piston speed until about 8,000 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 4 cylinders displaces 38.1 ci (624 cc).
9.5:1 is in the range that usually runs on pump premium.
It is one of 9 engines in the 9A2 Evo family, sitting between the 121.3 ci and 243.9 ci members.
| Displacement | 152.4 ci / 2.5 L |
|---|---|
| Bore | 4.0157" |
| Stroke | 3.0079" |
| Cylinders | 4 |
| Compression ratio | 9.5:1 |
| Bore/stroke ratio | 1.335 |
| Fuel type | gas |
|---|
| Bore/stroke character | 1.335 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,008 ft/min — conservative for a street engine |
| Displacement per cylinder | 38.1 ci |
| Static compression | 9.5:1 — in the range that usually runs on pump premium |
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