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Mazda 15 I4 specs: 1.496L (91.3 ci) 4-cylinder, 74.5 x 85.8 mm (2.9331 x 3.3780 in) bore and stroke, 13:1 compression. Rated 131 hp. DOHC.
The Mazda 15 I4 is undersquare — the 3.378" stroke exceeds the 2.9331" bore by 13.2% — a layout that trades peak RPM for leverage and torque low in the range. The 3.378" stroke does not reach 4,000 ft/min of mean piston speed until about 7,100 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 4 cylinders displaces 22.8 ci (374 cc).
13:1 on aluminum heads is high for a production gasoline engine; running a ratio like that on pump fuel depends on chamber design and fuel delivery rather than the number alone.
It is one of 13 engines in the Skyactiv-G family, the smallest at 91.3 ci. Factory fitments include the Mazda MX-5 Miata (ND), Mazda2, Mazda3 and 1 other.
| Displacement | 91.3 ci / 1.496 L |
|---|---|
| Bore | 2.9331" |
| Stroke | 3.378" |
| Cylinders | 4 |
| Compression ratio | 13:1 |
| Bore/stroke ratio | 0.868 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 131 hp |
| Bore/stroke character | 0.868 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 3,378 ft/min — conservative for a street engine |
| Displacement per cylinder | 22.8 ci |
| Static compression | 13:1 — high enough that pump premium or better is normally required |
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