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Mitsubishi 3A92 specs: 1.2L (73 ci) 3-cylinder, 75 x 90 mm (2.9528 x 3.5433 in) bore and stroke, 11:1 compression. Rated 78 hp. Rod ratio and piston speed.
The Mitsubishi 3A92 is undersquare — the 3.5433" stroke exceeds the 2.9528" bore by 16.7% — a layout that trades peak RPM for leverage and torque low in the range. The 3.5433" stroke puts mean piston speed at 4,000 ft/min around 6,750 RPM, which is where a production bottom end is generally considered at its limit. Each of the 3 cylinders displaces 24.3 ci (399 cc).
11:1 on aluminum heads is high enough that pump premium or better is normally required.
Factory fitments include the Mirage, Attrage.
| Displacement | 73 ci / 1.2 L |
|---|---|
| Bore | 2.9528" |
| Stroke | 3.5433" |
| Cylinders | 3 |
| Compression ratio | 11:1 |
| Bore/stroke ratio | 0.833 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 78 hp |
| Bore/stroke character | 0.833 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 3,543 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 24.3 ci |
| Static compression | 11:1 — high enough that pump premium or better is normally required |
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