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BMW S65B40 specs: 4.0L (244 ci) 8-cylinder, 92 x 75.2 mm (3.6220 x 2.9606 in) bore and stroke, 12:1 compression. Rated 414 hp, 2008–2013.
The BMW S65B40 is oversquare — the 3.622" bore exceeds the 2.9606" stroke by 22.3% — a layout that favors airflow and RPM over leverage at the crank. The 2.9606" stroke does not reach 4,000 ft/min of mean piston speed until about 8,100 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 8 cylinders displaces 30.5 ci (500 cc).
12:1 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.
6 factory variants share these dimensions, rated at 414 hp across 2008–2013.
| Displacement | 244 ci / 4 L |
|---|---|
| Bore | 3.622" |
| Stroke | 2.9606" |
| Cylinders | 8 |
| Configuration | V8 |
| Compression ratio | 12:1 |
| Bore/stroke ratio | 1.223 |
| Fuel type | gas |
|---|---|
| Firing order | 1-5-4-8-7-2-6-3 |
| Advertised HP | 414 hp |
| Years | 2008–2013 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. |
|---|---|---|---|---|
| 2008 | S65B40 net | 414 @ 8300 | 295 lb-ft @ 3900 | 12:1 |
| 2009 | S65B40 net | 414 @ 8300 | 295 lb-ft @ 3900 | 12:1 |
| 2010 | S65B40 net | 414 @ 8300 | 295 lb-ft @ 3900 | 12:1 |
| 2011 | S65B40 net | 414 @ 8300 | 295 lb-ft @ 3900 | 12:1 |
| 2012 | S65B40 net | 414 @ 8300 | 295 lb-ft @ 3900 | 12:1 |
| 2013 | S65B40 net | 414 @ 8300 | 295 lb-ft @ 3900 | 12:1 |
Factory specification sheet.
| Bore/stroke character | 1.223 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 2,961 ft/min — conservative for a street engine |
| Displacement per cylinder | 30.5 ci |
| Static compression | 12:1 — 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 |
|---|---|---|
| 2008 | 414 hp | S65B40 |
| 2009 | 414 hp | S65B40 |
| 2010 | 414 hp | S65B40 |
| 2011 | 414 hp | S65B40 |
| 2012 | 414 hp | S65B40 |
| 2013 | 414 hp | S65B40 |
1 factory vehicle, 2008–2013. Each year opens that model's engine table.