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BMW S50B30 US specs: 3.0L (182.7 ci) 6-cylinder, 86 x 85.8 mm (3.3858 x 3.3780 in) bore and stroke, 10.5:1 compression. Rated 240 hp. DOHC.
The BMW S50B30 US is close to square: 3.3858" bore against 3.378" stroke, within 0.2%, which splits the difference between a high-revving layout and a torque layout. The 3.378" stroke does not reach 4,000 ft/min of mean piston speed until about 7,100 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 6 cylinders displaces 30.5 ci (499 cc).
10.5:1 on aluminum heads is in the range that usually runs on pump premium; aluminum sheds heat faster than iron, which makes the same number a little more forgiving.
It is one of 5 engines in the S5x family, the smallest at 182.7 ci. Factory fitments include the BMW E36 M3 (US-spec).
| Displacement | 182.7 ci / 3 L |
|---|---|
| Bore | 3.3858" |
| Stroke | 3.378" |
| Cylinders | 6 |
| Compression ratio | 10.5:1 |
| Bore/stroke ratio | 1.002 |
| Block material | cast iron |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 240 hp |
| Bore/stroke character | 1.002 — square — bore and stroke are within 5%, a balanced compromise |
|---|---|
| Mean piston speed at 6,000 RPM | 3,378 ft/min — conservative for a street engine |
| Displacement per cylinder | 30.4 ci |
| Static compression | 10.5:1 — in the range that usually runs on pump premium |
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