1936 Aero Type 50

One of the inherent problems with two-stroke engines was that the larger the cylinder capacity, the less efficient the engine became. DKW struggled to lift the capacity of their twin-cylinder engines much above 700cc. A rebored 1100cc twin cylinder engine was developed but its performance was deemed so 'sloppy' that it was relegated to industrial use only.

In Czechoslovakia, Aero and Z developed twin-cylinder two-stroke engines of 1 litre capacity that generated power in the 30 to 50 horsepower range, far in excess of the DKW 700cc engine's meagre 18-20 horsepower. This was the developmental limit for a twin-cylinder two-stroke, so both Aero and Z addressed the problem by adopting four-cylinder two-stroke engines of 2 litre capacity. This engine was used in their premium vehicle range, the Aero Type 50.

Aero was so confident about the soundness of both their twin and four cylinder engines that they expected to license their manufacture back to DKW, who were at the time struggling to develop the two-stroke triple. Unfortunately, these plans came to nought when Germany invaded Czechoslovakia in 1938. Both Aero and Z had their production curtailed by the National Socialist's Schell plan and they were diverted to military production.