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Mazda 13B specs: 1.308L (79.8 ci) 2-cylinder. Rated 110-160 hp, 1974–1991. Used in the Mazda B-Series and Mazda RX-4. Rotary. Rod ratio and piston speed.
The Mazda Rotary (13B) 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 39.9 ci (654 cc).
It is one of 16 engines in the Rotary family, sitting between the 59.9 ci and 119.7 ci members. 14 factory variants share these dimensions, rated from 110 to 160 hp across 1974–1991.
| Displacement | 79.8 ci / 1.308 L |
|---|---|
| Cylinders | 2 |
| Bore/stroke ratio | 1.125 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | Rotary |
| Fuel type | gas |
| Advertised HP | 110–160 hp |
| Years | 1974–1991 |
These records share identical bore, stroke, displacement and compression. They differ by model year and factory power rating.
| Year | Advertised HP | Code |
|---|---|---|
| 1974 | 110 hp | 13B |
| 1975 | — | 13B |
| 1975 | 110 hp | 13B |
| 1976 | 110 hp | 13B |
| 1977 | 110 hp | 13B |
| 1978 | 110 hp | 13B |
| 1984 | 135 hp | 13B |
| 1985 | 135 hp | 13B |
| 1986 | 146 hp | 13B |
| 1987 | 146 hp | 13B |
| 1988 | 146 hp | 13B |
| 1989 | 160 hp | 13B |
| 1990 | 160 hp | 13B |
| 1991 | 160 hp | 13B |
4 factory vehicles, 1974–1991. Each year opens that model's engine table.