Hispano-Suiza 12Z
| Hispano-Suiza 12Z | |
|---|---|
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| Type | V-12 liquid-cooled piston engine |
| National origin | France |
| Manufacturer | Hispano-Suiza |
| Major applications |
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| Developed from | Hispano-Suiza 12Y |
The 12Z, designated Type 89 by the company, was the final evolution of the series of Hispano-Suiza V-12 aircraft engines, which had just entered production when France fell to the Germans during World War II. A small number were produced during the war but the German occupation government would not allow full-scale production to start. After the war small numbers were built to equip new designs, but the rapid introduction of the jet engine ended further development.
The 12Z differed from the earlier 12Y primarily in the use of four valves per cylinder operated by dual overhead cams. This gave the cylinders considerably better volumetric efficiency and faster operation, raising the RPM from 2,400 to 2,700. The engine was also designed to run only on 100 octane fuel (instead of 87, which was common at that point) which allowed the compression ratio to rise from the 12Y's 5.8:1 to the 12Z's 6.75:1. These changes raised the power from 1,000 to 1,300 hp (750 to 970 kW) at sea level.
Unfortunately the engine continued to use a single-stage, single-speed supercharger and therefore lacked the all-altitude performance of German and British designs. But tuning the supercharger for a different critical altitude improved high-altitude performance considerably, delivering 1,500 hp (1,120 kW) at 6,400 m (21,000 ft) as opposed to 930 hp (690 kW) at 900 m (3,000 ft) for the 12Y.
Small prototype runs started in 1939, and were fitted to the French Air Force's front-line fighter aircraft, the M.S.410 and D.520, creating the M.S.450 and D.524 respectively. Production of the main model, the 12Z-17, was just starting at the time of the armistice. Production was undertaken in Hispano-Suiza's Spanish factories, but these engines had many problems and were never used in any numbers.
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Wikipedia