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Audi AMB / BEX specs: 1.8L (109 ci) 4-cylinder, 81 x 86.4 mm (3.1890 x 3.4016 in) bore and stroke. Rated 170 hp, 2002–2006. Used in the Audi A4 / S4. DOHC.
The Audi AMB / BEX is undersquare — the 3.4016" stroke exceeds the 3.189" bore by 6.3% — a layout that trades peak RPM for leverage and torque low in the range. The 3.4016" stroke does not reach 4,000 ft/min of mean piston speed until about 7,050 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 4 cylinders displaces 27.3 ci (447 cc).
It is one of 4 engines in the EA113 family, the smallest at 109 ci. 5 factory variants share these dimensions, rated at 170 hp across 2002–2006.
| Displacement | 109 ci / 1.8 L |
|---|---|
| Bore | 3.189" |
| Stroke | 3.4016" |
| Cylinders | 4 |
| Configuration | I4 |
| Compression ratio | 9.3–9.5:1 (published figures vary) |
| Bore/stroke ratio | 0.938 |
| Block material | cast iron |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 170 hp |
| Years | 2002–2006 |
| Bore/stroke character | 0.938 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 3,402 ft/min — conservative for a street engine |
| Displacement per cylinder | 27.3 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 |
|---|---|---|
| 2002 | 170 hp | AMB / BEX |
| 2003 | 170 hp | AMB / BEX |
| 2004 | 170 hp | AMB / BEX |
| 2005 | 170 hp | AMB / BEX |
| 2006 | 170 hp | AMB / BEX |
1 factory vehicle, 2002–2006. Each year opens that model's engine table.