See other engines in this family
Subaru FB25 specs: 2.498L (152.4 ci) 4-cylinder, 94 x 90 mm (3.7008 x 3.5433 in) bore and stroke. Rated 170-194 hp, 2011–2026. Used in the Subaru Forester.
The Subaru FB25 is close to square: 3.7008" bore against 3.5433" stroke, within 4.4%, which splits the difference between a high-revving layout and a torque layout. The 3.5433" stroke puts mean piston speed at 4,000 ft/min around 6,750 RPM, which is where a production bottom end is generally considered at its limit. Each of the 4 cylinders displaces 38.1 ci (624 cc).
It is one of 8 engines in the FB family, the largest at 152.4 ci. 17 factory variants share these dimensions, rated from 170 to 194 hp across 2011–2026.
| Displacement | 152.4 ci / 2.498 L |
|---|---|
| Bore | 3.7008" |
| Stroke | 3.5433" |
| Cylinders | 4 |
| Compression ratio | 10–12:1 (published figures vary) |
| Bore/stroke ratio | 1.044 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 170–194 hp |
| Years | 2011–2026 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. |
|---|---|---|---|---|
| 2011 | FB25 net | 170 @ 5800 | 174 lb-ft @ 4100 | 10.5:1 |
| 2012 | FB25 net | 170 @ 5800 | 174 lb-ft @ 4100 | 10.5:1 |
| 2013 | FB25 net | 170 @ 5800 | 174 lb-ft @ 4100 | 10.5:1 |
| 2013 | FB25 net | 173 @ 5600 | 174 lb-ft @ 4100 | 10:1 |
| 2014 | FB25 net | 170 @ 5800 | 174 lb-ft @ 4100 | 10:1 |
| 2014 | FB25 net | 173 @ 5600 | 174 lb-ft @ 4100 | 10:1 |
| 2015 | FB25 net | 170 @ 5800 | 174 lb-ft @ 4100 | 10:1 |
| 2015 | FB25 net | 175 @ 5800 | 174 lb-ft @ 4000 | 10.3:1 |
| 2016 | FB25 net | 170 @ 5800 | 174 lb-ft @ 4100 | 10:1 |
| 2016 | FB25 net | 175 @ 5800 | 174 lb-ft @ 4000 | 10.3:1 |
| 2017 | FB25 net | 170 @ 5800 | 174 lb-ft @ 4100 | 10:1 |
| 2017 | FB25 net | 175 @ 5800 | 174 lb-ft @ 4000 | 10.3:1 |
| 2018 | FB25 net | 170 @ 5800 | 174 lb-ft @ 4100 | 10:1 |
| 2018 | FB25 net | 175 @ 5800 | 174 lb-ft @ 4000 | 10.3:1 |
| 2019 | FB25 net | 175 @ 5800 | 174 lb-ft @ 4000 | 10.3:1 |
| 2025 | FB25 net | 194 | — | 12:1 |
| 2026 | FB25 net | 194 | — | 12:1 |
Factory specification sheet.
| Bore/stroke character | 1.044 — square — bore and stroke are within 5%, a balanced compromise |
|---|---|
| Mean piston speed at 6,000 RPM | 3,543 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 38.1 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 |
|---|---|---|
| 2011 | 170 hp | FB25 |
| 2012 | 170 hp | FB25 |
| 2013 | 170 hp | FB25 |
| 2013 | 173 hp | FB25 |
| 2014 | 170 hp | FB25 |
| 2014 | 173 hp | FB25 |
| 2015 | 170 hp | FB25 |
| 2015 | 175 hp | FB25 |
| 2016 | 170 hp | FB25 |
| 2016 | 175 hp | FB25 |
| 2017 | 170 hp | FB25 |
| 2017 | 175 hp | FB25 |
| 2018 | 170 hp | FB25 |
| 2018 | 175 hp | FB25 |
| 2019 | 175 hp | FB25 |
| 2025 | 194 hp | FB25 |
| 2026 | 194 hp | FB25 |
3 factory vehicles, 2011–2026. Each year opens that model's engine table.