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The same engine also has a main page: Mazda 12A.
Mazda 12A specs: 1.1L (70 ci) 2-cylinder, 90 x 80 mm (3.5433 x 3.1496 in) bore and stroke, 9.4:1 compression. Rated 100 hp. Rod ratio and piston speed.
The Mazda Wankel (12A) is oversquare — the 3.5433" bore exceeds the 3.1496" stroke by 12.5% — a layout that favors airflow and RPM over leverage at the crank. 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 35.0 ci (574 cc).
9.4:1 on aluminum heads is low by modern standards and generally happy on regular pump fuel.
It is one of 3 engines in the Wankel family, the smallest at 70 ci. Factory fitments include the RX-7 SA22C, RX-3, Cosmo and 3 others.
| Displacement | 70 ci / 1.1 L |
|---|---|
| Bore | 3.5433" |
| Stroke | 3.1496" |
| Cylinders | 2 |
| Compression ratio | 9.4:1 |
| Bore/stroke ratio | 1.125 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | Rotary |
| Fuel type | gas |
| Advertised HP | 100 hp |
| Bore/stroke character | 1.125 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,150 ft/min — conservative for a street engine |
| Displacement per cylinder | 35.0 ci |
| Static compression | 9.4:1 — low by modern standards, generally happy on regular pump fuel |
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