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Acura F20C specs: 2.0L (121.9 ci) 4-cylinder, 87 x 84.4 mm (3.4252 x 3.3228 in) bore and stroke, 11.7:1 compression. Rated 240 hp. Rod ratio and piston speed.
The Acura F20C is close to square: 3.4252" bore against 3.3228" stroke, within 3.1%, which splits the difference between a high-revving layout and a torque layout. The 3.3228" stroke does not reach 4,000 ft/min of mean piston speed until about 7,200 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).
11.7:1 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 2 engines in the Honda F-series family, the smallest at 121.9 ci. Factory fitments include the Honda S2000 (Japan/Europe/US 1999-2003), Honda S2000 (Japan 2004-2005).
| Displacement | 121.9 ci / 2 L |
|---|---|
| Bore | 3.4252" |
| Stroke | 3.3228" |
| Cylinders | 4 |
| Compression ratio | 11.7:1 |
| Bore/stroke ratio | 1.031 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 240 hp |
| Bore/stroke character | 1.031 — square — bore and stroke are within 5%, a balanced compromise |
|---|---|
| Mean piston speed at 6,000 RPM | 3,323 ft/min — conservative for a street engine |
| Displacement per cylinder | 30.5 ci |
| Static compression | 11.7:1 — high enough that pump premium or better is normally required |
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