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BMW M30B28 specs: 2.8L (170 ci) 6-cylinder, 86 x 80 mm (3.3858 x 3.1496 in) bore and stroke. Rated 169 hp, 1979–1981. Used in the BMW 5 Series.
The BMW M30B28 is oversquare — the 3.3858" bore exceeds the 3.1496" stroke by 7.5% — a layout that favors airflow and RPM over leverage at the crank. The 3.1496" stroke does not reach 4,000 ft/min of mean piston speed until about 7,600 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 6 cylinders displaces 28.3 ci (464 cc).
It is one of 3 engines in the BMW 170ci family, all of them 170 ci — the differences between them are in compression, heads and rating, not displacement. 3 factory variants share these dimensions, rated at 169 hp across 1979–1981.
| Displacement | 170 ci / 2.8 L |
|---|---|
| Bore | 3.3858" |
| Stroke | 3.1496" |
| Cylinders | 6 |
| Configuration | I6 |
| Bore/stroke ratio | 1.075 |
| Fuel type | gas |
|---|---|
| Advertised HP | 169 hp |
| Years | 1979–1981 |
| Bore/stroke character | 1.075 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,150 ft/min — conservative for a street engine |
| Displacement per cylinder | 28.3 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 |
|---|---|---|
| 1979 | 169 hp | M30B28 |
| 1980 | 169 hp | M30B28 |
| 1981 | 169 hp | M30B28 |
1 factory vehicle, 1979–1981. Each year opens that model's engine table.