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Porsche M97.21 specs: 3.4L (206.69 ci) 6-cylinder, 96 x 78 mm (3.7795 x 3.0709 in) bore and stroke, 11.1:1 compression. Rated 295 hp, 2006–2008.
The Porsche M97.21 is oversquare — the 3.7795" bore exceeds the 3.0709" stroke by 23.1% — a layout that favors airflow and RPM over leverage at the crank. The 3.0709" stroke does not reach 4,000 ft/min of mean piston speed until about 7,800 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 6 cylinders displaces 34.4 ci (565 cc).
11.1:1 is high enough that pump premium or better is normally required.
It is one of 6 engines in the M97 family, the smallest at 206.69 ci. 3 factory variants share these dimensions, rated at 295 hp across 2006–2008.
| Displacement | 206.69 ci / 3.4 L |
|---|---|
| Bore | 3.7795" |
| Stroke | 3.0709" |
| Cylinders | 6 |
| Compression ratio | 11.1:1 |
| Bore/stroke ratio | 1.231 |
| Fuel type | gas |
|---|---|
| Firing order | 1-6-2-4-3-5 |
| Advertised HP | 295 hp |
| Years | 2006–2008 |
| Bore/stroke character | 1.231 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,071 ft/min — conservative for a street engine |
| Displacement per cylinder | 34.4 ci |
| Static compression | 11.1:1 — high enough that pump premium or better is normally required |
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 |
|---|---|---|
| 2006 | 295 hp | M97.21 |
| 2007 | 295 hp | M97.21 |
| 2008 | 295 hp | M97.21 |
1 factory vehicle, 2006–2008. Each year opens that model's engine table.