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Acura K20A specs: 2.0L (121.9 ci) 4-cylinder, 86 x 86 mm (3.3858 x 3.3858 in) bore and stroke, 11.5:1 compression. Rated 217 hp. Rod ratio and piston speed.
The Acura K20A 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 (499 cc).
11.5:1 on aluminum heads is high for a production gasoline engine; running a ratio like that on pump fuel depends on chamber design and fuel delivery rather than the number alone.
It is one of 8 engines in the Honda K-series family, the smallest at 121.9 ci. Factory fitments include the Honda Integra Type R (DC5), Honda Civic Type R (EP3, FN2), Honda Accord Euro R (CL7).
| Displacement | 121.9 ci / 2 L |
|---|---|
| Bore | 3.3858" |
| Stroke | 3.3858" |
| Cylinders | 4 |
| Compression ratio | 11.5:1 |
| Bore/stroke ratio | 1 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 217 hp |
| 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 | 11.5:1 — high enough that pump premium or better is normally required |
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