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Kia Theta II G4KL specs: 2.0L (122 ci) 4-cylinder, 86 x 86 mm (3.3858 x 3.3858 in) bore and stroke, 10:1 compression. Rated 255 hp, 2018–2021.
The Kia Theta II G4KL is exactly square — 3.3858" bore and 3.3858" stroke are the same — which splits the difference between a high-revving layout and a torque layout. The 3.3858" stroke does not reach 4,000 ft/min of mean piston speed until about 7,100 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 4 cylinders displaces 30.5 ci (500 cc).
10:1 is in the range that usually runs on pump premium.
It is one of 2 engines in the Kia 122ci family, the largest at 122 ci. 4 factory variants share these dimensions, rated at 255 hp across 2018–2021.
| Displacement | 122 ci / 2 L |
|---|---|
| Bore | 3.3858" |
| Stroke | 3.3858" |
| Cylinders | 4 |
| Configuration | I4 |
| Compression ratio | 10:1 |
| Bore/stroke ratio | 1 |
| Fuel type | gas |
|---|---|
| Advertised HP | 255 hp |
| Years | 2018–2021 |
| Bore/stroke character | 1.000 — square — bore and stroke are within 5%, a balanced compromise |
|---|---|
| Mean piston speed at 6,000 RPM | 3,386 ft/min — conservative for a street engine |
| Displacement per cylinder | 30.5 ci |
| Static compression | 10:1 — in the range that usually runs on pump premium |
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 |
|---|---|---|
| 2018 | 255 hp | Theta II G4KL |
| 2019 | 255 hp | Theta II G4KL |
| 2020 | 255 hp | Theta II G4KL |
| 2021 | 255 hp | Theta II G4KL |
1 factory vehicle, 2018–2021. Each year opens that model's engine table.