V24 engine
A V24 engine is a 24-cylinder piston engine where two banks of twelve cylinders are arranged in a V-shaped configuration around a single crankshaft. The majority of V24 engines are "dual V12" engines, where two separate V12 engines are placed in line with each other. It has been used in certain equipment, like locomotives. Examples included the EMD E-series, these include the E9, which developed 2,400 hp, and E8, which made 2,250 hp.
Fiat AS.6 engine
The Fiat AS.6 engine was built in the early 1930s to power the Macchi M.C.72 plane, which was intended to compete in the 1931 Schneider Trophy air races. This engine was formed by mounting two Fiat AS.5 V12 engines one behind the other, with the front engine powering the rear propeller and the rear engine powering the front propeller. The combined displacement was more than and the combined power output was approximately.Mechanical problems prevented the airplane from competing. The Macchi M.C.72 achieved an average top speed of on 23 October 1934. This set the record for a piston-powered seaplane, which still stands.