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Acura K23A1 specs: 2.3L (140.3 ci) 4-cylinder, 86 x 99 mm (3.3858 x 3.8976 in) bore and stroke, 9:1 compression. Rated 240 hp. Rod ratio and piston speed.
The Acura K23A1 is undersquare — the 3.8976" stroke exceeds the 3.3858" bore by 13.1% — a layout that trades peak RPM for leverage and torque low in the range. The 3.8976" stroke puts mean piston speed at 4,000 ft/min around 6,150 RPM, which is where a production bottom end is generally considered at its limit. Each of the 4 cylinders displaces 35.1 ci (575 cc).
9:1 on aluminum heads is low by modern standards and generally happy on regular pump fuel.
It is one of 8 engines in the Honda K-series family, sitting between the 121.9 ci and 144 ci members. Factory fitments include the Acura RDX (TB1/TB2).
| Displacement | 140.3 ci / 2.3 L |
|---|---|
| Bore | 3.3858" |
| Stroke | 3.8976" |
| Cylinders | 4 |
| Compression ratio | 9:1 |
| Bore/stroke ratio | 0.869 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 240 hp |
| Bore/stroke character | 0.869 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 3,898 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 35.1 ci |
| Static compression | 9:1 — low by modern standards, generally happy on regular pump fuel |
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