The engines of utilitiy vehicles showed litlle difference to those found in motor cars, especially because these were often manufactured for wealthier people and had sufficient capacity and thus performance. As before, these were petrol engines, the Diesel engine existed only as a prototype. During the hardship years of the 1920s, the two-stroke engine was brought more and more into the foreground. From the mid-1930s until the end of the second world war, the two-stroke 'Schnürle' loop-scavenging looked forward to a promising future.
Indeed, let's go back to the 1920s. In the USA, the big companies now had research laboratories. The GM engineer Kettering and his team e.g, developed improvements in almost every aspect for the mass production. His fuel-developments, to improve the knocking resistance are famous, even though the additive proved later to be danger to health. Thus, in the course of 140 years, the compression ratio could be increased from just under 3:1 up to the 14:1 of today, this was favourable for possible performance and also for the achievable fuel consumption.
Another component, which went through almost constant improvement, is the piston. Because of it's oscillating movement, the weight-reduction was a great advantage. The first thrust in this direction took place around 1920 with the event of the miracle-material aluminium. Indeed, the beginning of this development was anything but simple, aluminium being the worst possible friction partner and that it also expands much more than the cast-iron of the cylinder block. One would have to come to grips with it, e.g., by applying a process of layering.
In the 1920s, the first thrust of the performance increase was followed by the development in the direction of higher RPM, which promised not only more performance, but also from distinctly lighter engines. This is where lighter pistons have a twofold advantage, however, the rest of the crank mechanism could not remain unchanged. The tendency was towards multi-layer bearings, which benefitted the utility vehicle engines, which were not stressed by high revs but by high torque.
At this time the designers had probably already entertained thoughts about charging the engines, they would however, not finally assert themselves until the 1930s. The racing scene, which up to now, was dominated by foreign countries, was now controlled, also through massive support from from the National-Socialist regime, by Mercedes and Auto Union. The combustion engines, 16 cylinders in the Auto Union, were run on a special mixture which made it possible for them to cope with the additional increased compression caused by charging. The performance of the engines exceeded anything seen before, world records were constantly being broken.
As early as the 1920s, two further related conditions for an effectively functioning automobile industry were established, the outsourcing of partial finishing to component suppliers and the standardisation. The complexity of a combustion engine alone, demanded too much of the capacities of a single manufacturer. Therefore, they farmed out the development, indeed under very strict guide-lines. The subsequent fitting together of the parts however, was only partially solved by the standardisation process.