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Kia G4NG specs: 2.0L (121.95 ci) 4-cylinder, 81 x 97 mm (3.1890 x 3.8189 in) bore and stroke. Built 2017–2020. Used in the Hyundai Sonata and Kia Optima / K5.
The Kia G4NG is undersquare — the 3.8189" stroke exceeds the 3.189" bore by 16.5% — a layout that trades peak RPM for leverage and torque low in the range. The 3.8189" stroke puts mean piston speed at 4,000 ft/min around 6,300 RPM, which is where a production bottom end is generally considered at its limit. Each of the 4 cylinders displaces 30.5 ci (500 cc).
It is one of 16 engines in the Smartstream family, sitting between the 61.02 ci and 213.58 ci members. 4 factory variants share these dimensions across 2017–2020.
| Displacement | 121.95 ci / 2 L |
|---|---|
| Bore | 3.189" |
| Stroke | 3.8189" |
| Cylinders | 4 |
| Configuration | I4 |
| Bore/stroke ratio | 0.835 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Years | 2017–2020 |
| Bore/stroke character | 0.835 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 3,819 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 30.5 ci |
Each link opens the calculator with this engine's specs already filled in.
These records share identical bore, stroke, displacement and compression. They differ by model year and factory power rating.
| Year | Advertised HP | Code |
|---|---|---|
| 2017 | — | G4NG |
| 2018 | — | G4NG |
| 2019 | — | G4NG |
| 2020 | — | G4NG |
2 factory vehicles, 2016–2020. Each year opens that model's engine table.