See other engines in this family
The same engine also has a main page: Mazda 12A Turbo.
Mazda 12A Turbo specs: 1.1L (70 ci) 2-cylinder, 105 x 70 mm (4.1339 x 2.7559 in) bore and stroke, 8.5:1 compression. Rated 160 hp. Rod ratio and piston speed.
The Mazda 12A Turbo is oversquare — the 4.1339" bore exceeds the 2.7559" stroke by 50.0% — a layout that favors airflow and RPM over leverage at the crank. The 2.7559" stroke does not reach 4,000 ft/min of mean piston speed until about 8,700 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).
8.5:1 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 Cosmo HB, Luce, Mazda RX-7 (FB) and 2 others.
| Displacement | 70 ci / 1.1 L |
|---|---|
| Bore | 4.1339" |
| Stroke | 2.7559" |
| Cylinders | 2 |
| Compression ratio | 8.5:1 |
| Bore/stroke ratio | 1.5 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | Rotary |
| Fuel type | gas |
| Advertised HP | 160 hp |
| Bore/stroke character | 1.500 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 2,756 ft/min — conservative for a street engine |
| Displacement per cylinder | 35.0 ci |
| Static compression | 8.5:1 — low by modern standards, generally happy on regular pump fuel |
Each link opens the calculator with this engine's specs already filled in.