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Mitsubishi 4B12 specs: 2.4L (146 ci) 4-cylinder, 88 x 97 mm (3.4646 x 3.8189 in) bore and stroke, 10.5:1 compression. Rated 168 hp, 2009–2017.
The Mitsubishi 4B12 is undersquare — the 3.8189" stroke exceeds the 3.4646" bore by 9.3% — a layout that trades peak RPM for leverage and torque low in the range. The 3.8189" stroke puts mean piston speed at 4,000 ft/min around 6,300 RPM, which is where a production bottom end is generally considered at its limit. Each of the 4 cylinders displaces 36.5 ci (598 cc).
10.5:1 is in the range that usually runs on pump premium.
It is one of 5 engines in the Mitsubishi 146ci family, all of them 146 ci — the differences between them are in compression, heads and rating, not displacement. 9 factory variants share these dimensions, rated at 168 hp across 2009–2017.
| Displacement | 146 ci / 2.4 L |
|---|---|
| Bore | 3.4646" |
| Stroke | 3.8189" |
| Cylinders | 4 |
| Configuration | I4 |
| Compression ratio | 10.5:1 |
| Bore/stroke ratio | 0.907 |
| Fuel type | gas |
|---|---|
| Redline | 6,500 rpm (factory limit) |
| Advertised HP | 168 hp |
| Years | 2009–2017 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. |
|---|---|---|---|---|
| 2009 | 4B12 net | 168 @ 6000 | 167 lb-ft @ 4100 | 10.5:1 |
| 2010 | 4B12 net | 168 @ 6000 | 167 lb-ft @ 4100 | 10.5:1 |
| 2011 | 4B12 net | 168 @ 6000 | 167 lb-ft @ 4100 | 10.5:1 |
| 2012 | 4B12 net | 168 @ 6000 | 167 lb-ft @ 4100 | 10.5:1 |
| 2013 | 4B12 net | 168 @ 6000 | 167 lb-ft @ 4100 | 10.5:1 |
| 2014 | 4B12 net | 168 @ 6000 | 167 lb-ft @ 4100 | 10.5:1 |
| 2015 | 4B12 net | 168 @ 6000 | 167 lb-ft @ 4100 | 10.5:1 |
| 2016 | 4B12 net | 168 @ 6000 | 167 lb-ft @ 4100 | 10.5:1 |
| 2017 | 4B12 net | 168 @ 6000 | 167 lb-ft @ 4100 | 10.5:1 |
Factory specification sheet.
| Bore/stroke character | 0.907 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 3,819 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 36.5 ci |
| Static compression | 10.5:1 — in the range that usually runs on pump premium |
Each link opens the calculator with this engine's specs already filled in.
These records share identical bore, stroke, displacement and compression. They differ by model year and factory power rating.
| Year | Advertised HP | Code |
|---|---|---|
| 2009 | 168 hp | 4B12 |
| 2010 | 168 hp | 4B12 |
| 2011 | 168 hp | 4B12 |
| 2012 | 168 hp | 4B12 |
| 2013 | 168 hp | 4B12 |
| 2014 | 168 hp | 4B12 |
| 2015 | 168 hp | 4B12 |
| 2016 | 168 hp | 4B12 |
| 2017 | 168 hp | 4B12 |
1 factory vehicle, 2009–2017. Each year opens that model's engine table.