Bore, stroke, displacement and compression for all 3 Mazda Wankel engines, compared side by side. Plus rod ratio and head specs where published.
| Displacement | 70–80 ci |
|---|---|
| Cylinders | 2 |
| Bore | 3.150–4.134" |
| Stroke | 2.756–3.150" |
| Compression | 8.5–9.4:1 |
| Advertised power | 100–255 hp |
| Engine | Displacement | Bore × Stroke | CR | HP |
|---|---|---|---|---|
| 13B-REW | 80 ci | 3.1496" × 3.1496" | 9:1 | 255 |
| 12A | 70 ci | 3.5433" × 3.1496" | 9.4:1 | 100 |
| 12A Turbo | 70 ci | 4.1339" × 2.7559" | 8.5:1 | 160 |
Both bore and stroke vary across the family, so these are separate castings rather than variations on one block.
2 of 3 are oversquare — bore larger than stroke, which favours revs over low-end torque.
Each engine page carries rod ratio, mean piston speed, bore/stroke character and cylinder head specs where published, and links into the calculators with its dimensions already filled in.