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Audi BBK / BHF specs: 4.2L (255 ci) 8-cylinder, 84.5 x 92.8 mm (3.3268 x 3.6535 in) bore and stroke, 11:1 compression. Rated 340 hp, 2004–2009.
The Audi BBK / BHF is undersquare — the 3.6535" stroke exceeds the 3.3268" bore by 8.9% — a layout that trades peak RPM for leverage and torque low in the range. The 3.6535" stroke puts mean piston speed at 4,000 ft/min around 6,550 RPM, which is where a production bottom end is generally considered at its limit. Each of the 8 cylinders displaces 31.9 ci (522 cc).
11:1 is high enough that pump premium or better is normally required.
6 factory variants share these dimensions, rated at 340 hp across 2004–2009.
| Displacement | 255 ci / 4.2 L |
|---|---|
| Bore | 3.3268" |
| Stroke | 3.6535" |
| Cylinders | 8 |
| Configuration | V8 |
| Compression ratio | 11:1 * |
| Bore/stroke ratio | 0.911 |
* Compression ratio from a single source; not yet cross-verified.
| Fuel type | gas |
|---|---|
| Advertised HP | 340 hp |
| Years | 2004–2009 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. |
|---|---|---|---|---|
| 2008 | BBK / BHF net | 340 @ 7000 | 302 lb-ft @ 3500 | 11:1 |
| 2009 | BBK / BHF net | 340 | — | — |
Factory specification sheet.
| Bore/stroke character | 0.911 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 3,654 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 31.9 ci |
| Static compression | 11:1 — 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 |
|---|---|---|
| 2004 | — | BBK / BHF |
| 2005 | — | BBK / BHF |
| 2006 | — | BBK / BHF |
| 2007 | — | BBK / BHF |
| 2008 | 340 hp | BBK / BHF |
| 2009 | 340 hp | BBK / BHF |
1 factory vehicle, 2004–2009. Each year opens that model's engine table.