Wright Hispano-Suiza E-2 & E-4 - USA
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Fig 1. Wright Hispano-Suiza Aviation Engine, Model E-2.

Wright Water-Cooled Engines. Improvements made by Wright engineers in 1922, produced an aircraft engine that operated for longer periods at higher mean effective pressures than any other type of internal combustion engine at the time. Several types weighing less than 2-1/2 pounds per horsepower were tested for periods of from 200 to 300 hours and required little attention. The Wright E4, with the same crankcase assembly, the cylinders only being changed, ran for 572 hours without attention of any kind. Compared with the original Model A, built 10 years before, the new engine with approximately the same weight and same displacement, developed one third more power, operated at 24 per cent more speed and had 3,000 per cent greater durability.

Fig 2. Wright 200 Horsepower Aviation Engine, Model E-4 has Eight Water-cooled Cylinders in Two Blocks of Four.

During WW I, exhaust valves, connecting rod big end bearings and spark plugs gave the most trouble. In cylinder construction three difficulties presented themselves: (a) the valves warped and burned, (b) the valve seats did not remain true and (c) in long runs the valves hammered into the seats so that the tappet clearance was lost and the valves were held open. The new type of Wright cylinder as shown at Fig. 3, and the use of tulip head silchrome steel valves greatly reduced valve troubles. Refinement of details of the 1,947 cubic inches 60 degree V-type 12-cylinder Wright T-3 engine enabled it to be used satisfactorily at speeds greater than 2,200 rpm, and to develop 750 horsepower with approximately 140 pounds mean-effective pressure at 20 per cent less weight per horsepower than that of the original engine.

Fig 3. Wright "Tempest" E-4 water-cooled engine viewed from the rear showing magneto mounting and water pump location.

After the Wright E2 engine, shown at Fig. 1 went out of production, it remained a popular type for some years. This engine had practically all of the characteristics of the Hispano-Suiza as previously described. The improved and refined Wright E4 shown at Figs. 2, 3 and 4 is the type that had been operated for 310 hours with one cylinder assembly, or long enough to have driven an airplane 31,000 miles without overhauling. After a new set of cylinders had been fitted, the other parts were run an additional amount so that the equivalent of 57,200 miles operation was obtained with only minor external adjustments. The old Model A engines developed a maximum of 175 horsepower at 1,800 rpm, whereas the latest models of the same type developed a maximum of 285 horsepower at 2,300 rpm. The bore of the E4 cylinders was 4.710 inches, the stroke was 5.110 inches and the total displacement was 718 cubic inches. The engine went out of production when all demands for this amount of horsepower was supplied with radial air-cooled engines.

Fig 4. Top view of the Wright "Tempest" E-4 water-cooled engine showing carburetor and induction manifolding.