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Hyundai G4HC specs: 1.0L (61 ci) 4-cylinder, 66 x 73 mm (2.5984 x 2.8740 in) bore and stroke, 9.6:1 compression. Rated 60 hp. Rod ratio and piston speed.
The Hyundai G4HC is undersquare — the 2.874" stroke exceeds the 2.5984" bore by 9.6% — a layout that trades peak RPM for leverage and torque low in the range. The 2.874" stroke does not reach 4,000 ft/min of mean piston speed until about 8,350 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 4 cylinders displaces 15.3 ci (250 cc).
9.6:1 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, sitting between the 48.8 ci and 67.1 ci members. Factory fitments include the Hyundai Atos, Hyundai Getz, Kia Picanto and 1 other.
| Displacement | 61 ci / 1 L |
|---|---|
| Bore | 2.5984" |
| Stroke | 2.874" |
| Cylinders | 4 |
| Compression ratio | 9.6:1 |
| Bore/stroke ratio | 0.904 |
| Block material | cast iron |
|---|---|
| Head material | aluminum |
| Valvetrain | SOHC |
| Fuel type | gas |
| Advertised HP | 60 hp |
| Bore/stroke character | 0.904 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 2,874 ft/min — conservative for a street engine |
| Displacement per cylinder | 15.3 ci |
| Static compression | 9.6:1 — in the range that usually runs on pump premium |
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