[4] He developed an inverted air-cooled six-cylinder engine for use in a privately entered Caudron C.366 to compete in the Coupe Deutsch de Meurthe air race in 1934.
[5][3] On 6 January 1934, one of his engines, mounted in a Caudron C.362, set a new 1,000-kilometer speed record of 332.8 km/h (206.8 mph) for light aircraft; this was six days too late to claim a 50,000-franc prize from the French air ministry.
[7] The Régnier engine powered a Percival Mew Gull to victory in the Coupe Armand Esders in July 1935 at 302 km/h.
[2] On 4 September 1940, Émile Régnier died,[11] but his company continued and was subsequently captured by the Nazis after the invasion of France during World War II.
[12][13] During the Occupation of France and in the years shortly after World War II, the Régnier company designed and produced a set of three simplified four-cylinder inverted air-cooled inline engines of increasing capacity and power, the 4J, 4K and 4L.