During the First World War, the aeronautic sector went through a rapid development dictated by the pressing demand for aircraft with higher performances. This has led many companies to put effort into the design of new aircraft and the development of their engines. In Italy, one of the most important was FIAT, which since the '10s had started the autonomous production of both aircraft and engines. The FIAT A.12 bis engine was developed in 1917 as an evolution of the A.12 model, to improve its overall performance and technical qualities. The engine has the typical technical features of liquid-cooled engines used in aviation during that period, deriving from a constructive scheme introduced by Mercedes. Cylinders and heads were constructed of steel with thin-walled weld-steel cooling jackets; the parts of the valve timing system were enclosed in carter that ensured the correct lubrication. This allowed to contain the total mass of the engine, obtaining a good reliability and a certain simplification in production; various modifications could be easily introduced quickly, without substantial changes to the general layout.The engine, produced in large series (over 12,000 copies) since 1917, was considered one of the best in its class and was used, in the early '20s, in numerous Italian and foreign aircraft (French, English, Russians et al.). In Great Britain it was sold at a higher price than some engines produced by other well-known manufacturers and at the same price as the Rolls Royce Eagle, one of the most powerful of that period. After the war, some FIAT A.12 bis were also used in motorsport. With some modifications, a specimen was used to equip the Fiat SB4 Mefistofele record-breaking car, built and led by the British pilot Ernest Eldridge, who in 1924 obtained the world speed record, reaching 234.97 km/h. Similarly, another FIAT A.12 bis was used for the record-breaking Botafogo Special car, built by Argentine pilot Adolfo Scandroglio.