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Mitsubishi 4N15 specs: 2.4L (149 ci) 4-cylinder, 86 x 105.1 mm (3.3858 x 4.1378 in) bore and stroke, 15.5:1 compression. Rated 178 hp. DOHC.
The Mitsubishi 4N15 is undersquare — the 4.1378" stroke exceeds the 3.3858" bore by 18.2% — a layout that trades peak RPM for leverage and torque low in the range. The 4.1378" stroke puts mean piston speed at 4,000 ft/min around 5,800 RPM, which is where a production bottom end is generally considered at its limit. Each of the 4 cylinders displaces 37.3 ci (610 cc).
At 15.5:1 this is a compression-ignition engine: the ratio is the heat source that lights the fuel, not a knock limit to be managed.
It is one of 2 engines in the 4N1 family, the largest at 149 ci. Factory fitments include the L200 Triton, Pajero Sport, L200 and 1 other.
| Displacement | 149 ci / 2.4 L |
|---|---|
| Bore | 3.3858" |
| Stroke | 4.1378" |
| Cylinders | 4 |
| Compression ratio | 15.5:1 |
| Bore/stroke ratio | 0.818 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | diesel |
| Advertised HP | 178 hp |
| Bore/stroke character | 0.818 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 4,138 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 37.3 ci |
| Static compression | 15.5:1 — high enough that pump premium or better is normally required |
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