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Honda H23A specs: 2.3L (139 ci) 4-cylinder, 87 x 95 mm (3.4252 x 3.7402 in) bore and stroke, 9.8:1 compression. Rated 160 hp. Rod ratio and piston speed.
The Honda H23A is undersquare — the 3.7402" stroke exceeds the 3.4252" bore by 8.4% — a layout that trades peak RPM for leverage and torque low in the range. The 3.7402" stroke puts mean piston speed at 4,000 ft/min around 6,400 RPM, which is where a production bottom end is generally considered at its limit. Each of the 4 cylinders displaces 34.8 ci (569 cc).
9.8:1 on aluminum heads is in the range that usually runs on pump premium; aluminum sheds heat faster than iron, which makes the same number a little more forgiving.
It is one of 4 engines in the H-series family, the largest at 139 ci. Factory fitments include the Honda Prelude Si (JDM), Honda Accord SiR (JDM), Honda Accord 2.3i (EDM) and 2 others.
| Displacement | 139 ci / 2.3 L |
|---|---|
| Bore | 3.4252" |
| Stroke | 3.7402" |
| Cylinders | 4 |
| Compression ratio | 9.8:1 |
| Bore/stroke ratio | 0.916 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 160 hp |
| Bore/stroke character | 0.916 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 3,740 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 34.8 ci |
| Static compression | 9.8:1 — in the range that usually runs on pump premium |
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