Editing Diesel engine (section)

===Railroad rolling stock===
Diesel engines for locomotives are built for continuous operation between refuelings and may need to be designed to use poor quality fuel in some circumstances.<ref name="Reif_2014_12" /> Some locomotives use two-stroke diesel engines.<ref name="Merker_2014_284" /> Diesel engines have replaced [[Steam locomotive|steam engine]]s on all non-electrified railroads in the world. The first [[diesel locomotive]]s appeared in 1913,<ref name="Tschöke_2018_10" /> and [[diesel multiple units]] soon after. Nearly all modern diesel locomotives are more correctly known as [[diesel–electric locomotive]]s because they use an electric transmission: the diesel engine drives an electric generator which powers electric traction motors.<ref name="vB_2017_1289" /> While [[electric locomotive]]s have replaced the diesel locomotive for passenger services in many areas diesel traction is widely used for cargo-hauling [[freight train]]s and on tracks where electrification is not economically viable.

In the 1940s, road vehicle diesel engines with power outputs of {{convert|150|-|200|PS|kW hp}} were considered reasonable for DMUs. Commonly, regular truck powerplants were used. The height of these engines had to be less than {{convert|1|m}} to allow underfloor installation. Usually, the engine was mated with a pneumatically operated mechanical gearbox, due to the low size, mass, and production costs of this design. Some DMUs used hydraulic torque converters instead. Diesel–electric transmission was not suitable for such small engines.<ref name="Kremser_1942_22" /> In the 1930s, the [[Deutsche Reichsbahn]] standardised its first DMU engine. It was a {{convert|30.3|litre|cuin}}, 12-cylinder boxer unit, producing {{convert|275|PS|kW hp}}. Several German manufacturers produced engines according to this standard.<ref name="Kremser_1942_23" />