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Mitsubishi 4G63 specs: 2.0L (122 ci) 4-cylinder, 85 x 88 mm (3.3465 x 3.4646 in) bore and stroke, 10.5:1 compression. Rated 145 hp. DOHC.
The Mitsubishi 4G63 is close to square: 3.3465" bore against 3.4646" stroke, within 3.4%, which splits the difference between a high-revving layout and a torque layout. The 3.4646" stroke puts mean piston speed at 4,000 ft/min around 6,950 RPM, which is where a production bottom end is generally considered at its limit. Each of the 4 cylinders displaces 30.5 ci (500 cc).
10.5:1 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 9 engines in the Sirius family, the smallest at 122 ci. Factory fitments include the Eclipse GS, Galant GTI, Lancer and 3 others.
| Displacement | 122 ci / 2 L |
|---|---|
| Bore | 3.3465" |
| Stroke | 3.4646" |
| Cylinders | 4 |
| Compression ratio | 10.5:1 |
| Bore/stroke ratio | 0.966 |
| Block material | cast iron |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 145 hp |
| Bore/stroke character | 0.966 — square — bore and stroke are within 5%, a balanced compromise |
|---|---|
| Mean piston speed at 6,000 RPM | 3,465 ft/min — conservative for a street engine |
| Displacement per cylinder | 30.5 ci |
| Static compression | 10.5:1 — in the range that usually runs on pump premium |
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