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BMW S5x specs: 3.2L (195.2 ci) 6-cylinder, 87 x 91 mm (3.4252 x 3.5827 in) bore and stroke, 11.5:1 compression. Rated 333-360 hp. Rod ratio and piston speed.
The BMW S5x is close to square: 3.4252" bore against 3.5827" stroke, within 4.4%, which splits the difference between a high-revving layout and a torque layout. The 3.5827" stroke puts mean piston speed at 4,000 ft/min around 6,700 RPM, which is where a production bottom end is generally considered at its limit. Each of the 6 cylinders displaces 32.5 ci (533 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.
It is one of 5 engines in the S5x family, the largest at 195.2 ci. 3 factory variants share these dimensions, rated from 333 to 360 hp. Factory fitments include the BMW E46 M3 (US-spec), BMW Z3 M Roadster/Coupe (US-spec), BMW Z4 M Roadster/Coupe (US-spec) and 4 others.
| Displacement | 195.2 ci / 3.2 L |
|---|---|
| Bore | 3.4252" |
| Stroke | 3.5827" |
| Cylinders | 6 |
| Compression ratio | 11.5:1 |
| Bore/stroke ratio | 0.956 |
| Block material | cast iron |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 333–360 hp |
| Bore/stroke character | 0.956 — square — bore and stroke are within 5%, a balanced compromise |
|---|---|
| Mean piston speed at 6,000 RPM | 3,583 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 32.5 ci |
| Static compression | 11.5:1 — 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 |
|---|---|---|
| — | 333 hp | S54B32 |
| — | 343 hp | S54B32 |
| — | 360 hp | S54B32HP |