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Hyundai D4FB specs: 1.6L (97.6 ci) 4-cylinder, 77.2 x 84.5 mm (3.0394 x 3.3268 in) bore and stroke, 17.3:1 compression. Rated 128 hp. DOHC.
The Hyundai D4FB is undersquare — the 3.3268" stroke exceeds the 3.0394" bore by 8.6% — a layout that trades peak RPM for leverage and torque low in the range. The 3.3268" stroke does not reach 4,000 ft/min of mean piston speed until about 7,200 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 4 cylinders displaces 24.4 ci (400 cc).
At 17.3:1 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 U family, the largest at 97.6 ci. Factory fitments include the Hyundai i30, Hyundai Kona, Kia Ceed.
| Displacement | 97.6 ci / 1.6 L |
|---|---|
| Bore | 3.0394" |
| Stroke | 3.3268" |
| Cylinders | 4 |
| Compression ratio | 17.3:1 |
| Bore/stroke ratio | 0.914 |
| Block material | cast iron |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | diesel |
| Advertised HP | 128 hp |
| Bore/stroke character | 0.914 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 3,327 ft/min — conservative for a street engine |
| Displacement per cylinder | 24.4 ci |
| Static compression | 17.3:1 — high enough that pump premium or better is normally required |
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