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Mazda 13B (Carbureted) specs: 1.3L (80 ci) 2-cylinder, 80 x 80 mm (3.1496 x 3.1496 in) bore and stroke, 9.2:1 compression. Rated 110 hp. Rotary.
The Mazda 13B (Carbureted) is exactly square — 3.1496" bore and 3.1496" stroke are the same — which splits the difference between a high-revving layout and a torque layout. The 3.1496" stroke does not reach 4,000 ft/min of mean piston speed until about 7,600 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 2 cylinders displaces 40.0 ci (655 cc).
9.2:1 on aluminum heads is low by modern standards and generally happy on regular pump fuel.
It is one of 5 engines in the 13B family, all of them 80 ci — the differences between them are in compression, heads and rating, not displacement. Factory fitments include the Mazda RX-4, Mazda RX-5 (Cosmo AP).
| Displacement | 80 ci / 1.3 L |
|---|---|
| Bore | 3.1496" |
| Stroke | 3.1496" |
| Cylinders | 2 |
| Compression ratio | 9.2:1 |
| Bore/stroke ratio | 1 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | Rotary |
| Fuel type | gas |
| Advertised HP | 110 hp |
| Bore/stroke character | 1.000 — square — bore and stroke are within 5%, a balanced compromise |
|---|---|
| Mean piston speed at 6,000 RPM | 3,150 ft/min — conservative for a street engine |
| Displacement per cylinder | 40.0 ci |
| Static compression | 9.2:1 — low by modern standards, generally happy on regular pump fuel |
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