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Audi AFN specs: 1.9L (115.7 ci) 4-cylinder, 79.5 x 95.5 mm (3.1299 x 3.7598 in) bore and stroke, 19.5:1 compression. Rated 110 hp. Rod ratio and piston speed.
The Audi EA180 (AFN) is undersquare — the 3.7598" stroke exceeds the 3.1299" bore by 16.8% — a layout that trades peak RPM for leverage and torque low in the range. The 3.7598" stroke puts mean piston speed at 4,000 ft/min around 6,400 RPM, which is where a production bottom end is generally considered at its limit. Each of the 4 cylinders displaces 28.9 ci (474 cc).
At 19.5:1 this is a compression-ignition engine: the ratio is the heat source that lights the fuel, not a knock limit to be managed.
It is one of 2 engines in the EA180 family, the smallest at 115.7 ci. Factory fitments include the A4 (B5), A6 (C5), Audi A4 (B5) and 1 other.
| Displacement | 115.7 ci / 1.9 L |
|---|---|
| Bore | 3.1299" |
| Stroke | 3.7598" |
| Cylinders | 4 |
| Compression ratio | 19.5:1 |
| Bore/stroke ratio | 0.832 |
| Block material | cast iron |
|---|---|
| Head material | aluminum |
| Valvetrain | SOHC |
| Fuel type | diesel |
| Advertised HP | 110 hp |
| Bore/stroke character | 0.832 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 3,760 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 28.9 ci |
| Static compression | 19.5:1 — high enough that pump premium or better is normally required |
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