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BMW M73B54 specs: 5.4L (328 ci) 12-cylinder, 85 x 79 mm (3.3465 x 3.1102 in) bore and stroke. Rated 322 hp, 1995–2001. Used in the BMW 7 Series.
The BMW M73B54 is oversquare — the 3.3465" bore exceeds the 3.1102" stroke by 7.6% — a layout that favors airflow and RPM over leverage at the crank. The 3.1102" stroke does not reach 4,000 ft/min of mean piston speed until about 7,700 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 12 cylinders displaces 27.3 ci (448 cc).
7 factory variants share these dimensions, rated at 322 hp across 1995–2001.
| Displacement | 328 ci / 5.4 L |
|---|---|
| Bore | 3.3465" |
| Stroke | 3.1102" |
| Cylinders | 12 |
| Bore/stroke ratio | 1.076 |
| Fuel type | gas |
|---|---|
| Advertised HP | 322 hp |
| Years | 1995–2001 |
| Bore/stroke character | 1.076 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,110 ft/min — conservative for a street engine |
| Displacement per cylinder | 27.3 ci |
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 |
|---|---|---|
| 1995 | 322 hp | M73B54 |
| 1996 | 322 hp | M73B54 |
| 1997 | 322 hp | M73B54 |
| 1998 | 322 hp | M73B54 |
| 1999 | 322 hp | M73B54 |
| 2000 | 322 hp | M73B54 |
| 2001 | 322 hp | M73B54 |
1 factory vehicle, 1995–2001. Each year opens that model's engine table.