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Audi 42 V8 B6 B7 specs: 4.2L (254 ci) 8-cylinder, 84.5 x 92.8 mm (3.3268 x 3.6535 in) bore and stroke, 11:1 compression. Rated 340 hp.
The Audi 42 V8 B6 B7 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 31.8 ci (520 cc).
11:1 on aluminum heads is high enough that pump premium or better is normally required.
It is one of 11 engines in the EA824 family, sitting between the 244.1 ci and 317.4 ci members. Factory fitments include the Audi S4 (B6/B7), Audi A6 (C6), Audi S4 (B6) and 1 other.
| Displacement | 254 ci / 4.2 L |
|---|---|
| Bore | 3.3268" |
| Stroke | 3.6535" |
| Cylinders | 8 |
| Compression ratio | 11:1 |
| Bore/stroke ratio | 0.911 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 340 hp |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. |
|---|---|---|---|---|
| 2004 | BBK / BHF net | 340 @ 7000 | 302 lb-ft @ 3500 | 11:1 |
| 2005 | BBK / BHF net | 340 @ 7000 | 302 lb-ft @ 3500 | 11:1 |
| 2006 | BBK / BHF net | 340 @ 7000 | 302 lb-ft @ 3500 | 11:1 |
| 2007 | BHF net | 340 @ 7000 | 302 lb-ft @ 3500 | 11:1 |
| 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 | 31.8 ci |
| Static compression | 11:1 — high enough that pump premium or better is normally required |
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1 factory vehicle, 2004–2009. Each year opens that model's engine table.