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BMW S55B30 specs: 3.0L (182 ci) 6-cylinder, 84 x 89.6 mm (3.3071 x 3.5276 in) bore and stroke, 10.2:1 compression. Rated 425-453 hp, 2015–2018.
The BMW S55B30 is undersquare — the 3.5276" stroke exceeds the 3.3071" bore by 6.3% — a layout that trades peak RPM for leverage and torque low in the range. The 3.5276" stroke puts mean piston speed at 4,000 ft/min around 6,800 RPM, which is where a production bottom end is generally considered at its limit. Each of the 6 cylinders displaces 30.3 ci (497 cc).
10.2:1 is in the range that usually runs on pump premium.
It is one of 7 engines in the BMW 182ci family, all of them 182 ci — the differences between them are in compression, heads and rating, not displacement. 5 factory variants share these dimensions, rated from 425 to 453 hp across 2015–2018.
| Displacement | 182 ci / 3 L |
|---|---|
| Bore | 3.3071" |
| Stroke | 3.5276" |
| Cylinders | 6 |
| Configuration | I6 |
| Compression ratio | 10.2:1 |
| Bore/stroke ratio | 0.937 |
| Fuel type | gas |
|---|---|
| Advertised HP | 425–453 hp |
| Years | 2015–2018 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. |
|---|---|---|---|---|
| 2015 | S55B30 net | 425 @ 5500 | 406 lb-ft @ 1850 | — |
| 2016 | S55B30 net | 425 @ 5500 | 406 lb-ft @ 1850 | — |
| 2017 | S55B30 net | 425 @ 5500 | 406 lb-ft @ 1850 | — |
| 2018 | S55B30 net | 425 @ 5500 | 406 lb-ft @ 1850 | — |
| 2018 | S55B30T0 net | 453 @ 6250 | 443 lb-ft @ 4000 | 10.2:1 |
Factory specification sheet.
| Bore/stroke character | 0.937 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 3,528 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 30.3 ci |
| Static compression | 10.2:1 — in the range that usually runs on pump premium |
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 |
|---|---|---|
| 2015 | 425 hp | S55B30 |
| 2016 | 425 hp | S55B30 |
| 2017 | 425 hp | S55B30 |
| 2018 | 425 hp | S55B30 |
| 2018 | 453 hp | S55B30 |
1 factory vehicle, 2015–2018. Each year opens that model's engine table.