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Porsche M48/00 specs: 4.5L (275.3 ci) 8-cylinder, 93 x 83 mm (3.6614 x 3.2677 in) bore and stroke, 11.5:1 compression. Rated 340 hp. DOHC.
The Porsche M48/00 is oversquare — the 3.6614" bore exceeds the 3.2677" stroke by 12.0% — a layout that favors airflow and RPM over leverage at the crank. The 3.2677" stroke does not reach 4,000 ft/min of mean piston speed until about 7,350 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 8 cylinders displaces 34.4 ci (564 cc).
11.5:1 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.
Factory fitments include the Cayenne S, Cayenne S (955).
| Displacement | 275.3 ci / 4.5 L |
|---|---|
| Bore | 3.6614" |
| Stroke | 3.2677" |
| Cylinders | 8 |
| Compression ratio | 11.5:1 |
| Bore/stroke ratio | 1.12 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 340 hp |
| Bore/stroke character | 1.120 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,268 ft/min — conservative for a street engine |
| Displacement per cylinder | 34.4 ci |
| Static compression | 11.5:1 — high enough that pump premium or better is normally required |
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