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Ford Duratec 25 Atkinson specs: 152 ci (2.5L) 4-cylinder, 3.504 x 3.937 in (89 x 100 mm) bore and stroke, 12.3:1 compression. Rated 177-191 hp, 2009–2012.
The Ford Duratec 25 Atkinson is undersquare — the 3.937" stroke exceeds the 3.5039" bore by 11.0% — a layout that trades peak RPM for leverage and torque low in the range. The 3.937" stroke puts mean piston speed at 4,000 ft/min around 6,100 RPM, which is where a production bottom end is generally considered at its limit. Each of the 4 cylinders displaces 38.0 ci (623 cc).
12.3:1 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 3 engines in the Ford 152ci family, all of them 152 ci — the differences between them are in compression, heads and rating, not displacement. 7 factory variants share these dimensions, rated from 177 to 191 hp across 2009–2012.
| Displacement | 152 ci / 2.5 L |
|---|---|
| Bore | 3.5039" |
| Stroke | 3.937" |
| Cylinders | 4 |
| Configuration | I4 |
| Compression ratio | 12.3:1 * |
| Bore/stroke ratio | 0.89 |
* Compression ratio from a single source; not yet cross-verified.
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 177–191 hp |
| Years | 2009–2012 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. |
|---|---|---|---|---|
| 2010 | net | 191 | — | — |
| 2011 | net | 191 | — | — |
| 2012 | net | 191 | — | — |
Factory specification sheet.
| Bore/stroke character | 0.890 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 3,937 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 38.0 ci |
| Static compression | 12.3:1 — 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 |
|---|---|---|
| 2009 | 177 hp | Duratec 25 Atkinson |
| 2010 | 177 hp | Duratec 25 Atkinson |
| 2010 | 191 hp | Duratec 25 Atkinson |
| 2011 | 177 hp | Duratec 25 Atkinson |
| 2011 | 191 hp | Duratec 25 Atkinson |
| 2012 | 177 hp | Duratec 25 Atkinson |
| 2012 | 191 hp | Duratec 25 Atkinson |
2 factory vehicles, 2009–2012. Each year opens that model's engine table.