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Hyundai G4KM specs: 2.5L (152.6 ci) 4-cylinder, 88.5 x 101.5 mm (3.4843 x 3.9961 in) bore and stroke, 11.3:1 compression. Rated 191 hp. DOHC.
The Hyundai G4KM is undersquare — the 3.9961" stroke exceeds the 3.4843" bore by 12.8% — a layout that trades peak RPM for leverage and torque low in the range. The 3.9961" stroke puts mean piston speed at 4,000 ft/min around 6,000 RPM, which is where a production bottom end is generally considered at its limit. Each of the 4 cylinders displaces 38.2 ci (625 cc).
11.3:1 on aluminum heads is high enough that pump premium or better is normally required.
It is one of 5 engines in the Smartstream family, sitting between the 152.4 ci and 212.2 ci members. Factory fitments include the Hyundai Sonata, Hyundai Santa Fe, Kia K5 and 1 other.
| Displacement | 152.6 ci / 2.5 L |
|---|---|
| Bore | 3.4843" |
| Stroke | 3.9961" |
| Cylinders | 4 |
| Compression ratio | 11.3:1 |
| Bore/stroke ratio | 0.872 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 191 hp |
| Bore/stroke character | 0.872 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 3,996 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 38.1 ci |
| Static compression | 11.3:1 — high enough that pump premium or better is normally required |
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