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Audi 19 TDI I4 specs: 1.9L (115.9 ci) 4-cylinder, 79.5 x 95.5 mm (3.1299 x 3.7598 in) bore and stroke, 19:1 compression. Rated 90 hp. SOHC.
The Audi 19 TDI I4 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 29.0 ci (475 cc).
At 19:1 this is a compression-ignition engine: the ratio is the heat source that lights the fuel, not a knock limit to be managed.
Factory fitments include the Audi A3 (8L), Audi A4 (B5), Audi A6 (C4) and 3 others.
| Displacement | 115.9 ci / 1.9 L |
|---|---|
| Bore | 3.1299" |
| Stroke | 3.7598" |
| Cylinders | 4 |
| Compression ratio | 19:1 |
| Bore/stroke ratio | 0.832 |
| Block material | cast iron |
|---|---|
| Head material | aluminum |
| Valvetrain | SOHC |
| Fuel type | diesel |
| Advertised HP | 90 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 | 29.0 ci |
| Static compression | 19:1 — high enough that pump premium or better is normally required |
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