The engine was developed at the Walter factory as a further development of the very successful Walter Minor engine. With a weight increase of only 2 kg compared to the Minor, the engine’s power increased by 30 hp. Equipped with an electrically driven supercharger. Used in the Aero Ae‑145, Orlican L‑40 Meta Sokol, and Bucker T‑131PA Jungmann aircraft.
| Configuration | 4-cylinder inverted inline |
| Cooling | air |
| Compression ratio | 6.0 |
| Displacement | 3.98 l |
| Weight | 102 kg |
| Maximum power | 140 hp at 2700 rpm |
| Rated power | 115 hp at 2500 rpm |
