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Hyundai G4HG specs: 1.1L (67.1 ci) 4-cylinder, 67 x 78 mm (2.6378 x 3.0709 in) bore and stroke, 10.1:1 compression. Rated 66 hp. Rod ratio and piston speed.
The Hyundai G4HG is undersquare — the 3.0709" stroke exceeds the 2.6378" bore by 14.1% — a layout that trades peak RPM for leverage and torque low in the range. The 3.0709" stroke does not reach 4,000 ft/min of mean piston speed until about 7,800 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 4 cylinders displaces 16.8 ci (275 cc).
10.1:1 on aluminum heads is in the range that usually runs on pump premium; aluminum sheds heat faster than iron, which makes the same number a little more forgiving.
It is one of 3 engines in the Epsilon family, the largest at 67.1 ci. Factory fitments include the Hyundai i10, Hyundai Getz.
| Displacement | 67.1 ci / 1.1 L |
|---|---|
| Bore | 2.6378" |
| Stroke | 3.0709" |
| Cylinders | 4 |
| Compression ratio | 10.1:1 |
| Bore/stroke ratio | 0.859 |
| Block material | cast iron |
|---|---|
| Head material | aluminum |
| Valvetrain | SOHC |
| Fuel type | gas |
| Advertised HP | 66 hp |
| Bore/stroke character | 0.859 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 3,071 ft/min — conservative for a street engine |
| Displacement per cylinder | 16.8 ci |
| Static compression | 10.1:1 — in the range that usually runs on pump premium |
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