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Audi WK specs: 2.1L (131 ci) 5-cylinder, 79.5 x 86.4 mm (3.1299 x 3.4016 in) bore and stroke. Built 1980. Used in the Audi 5000. Rod ratio and piston speed.
The Audi 131ci (WK) is undersquare — the 3.4016" stroke exceeds the 3.1299" bore by 8.0% — 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 5 cylinders displaces 26.2 ci (429 cc).
It is one of 5 engines in the Audi 131ci family, all of them 131 ci — the differences between them are in compression, heads and rating, not displacement.
| Displacement | 131 ci / 2.1 L |
|---|---|
| Bore | 3.1299" |
| Stroke | 3.4016" |
| Cylinders | 5 |
| Bore/stroke ratio | 0.92 |
| Fuel type | gas |
|---|---|
| Years | 1980 |
| Bore/stroke character | 0.920 — 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 | 26.2 ci |
Each link opens the calculator with this engine's specs already filled in.
1 factory vehicle, 1980. Each year opens that model's engine table.