Comments by "" (@neutronalchemist3241) on "Caproni Vizzola F.4, F.5 and F.6; Forgotten Italian Job Lot" video.

What the Caproni Vizzola (not Vizolla) fighters excelled in was climb speed. A quite important feature (since fighters really don't use simple horizontal speed. They continually exchange altitude for speed and vice-versa). The climb time to 6000m among the first generation monoplane Italian fighters was 603 seconds, for the F.5, 623 seconds for the Reggiane 2000, 629 seconds for the Macchi 200 and 703 seconds for the FIAT G.50. The Isotta Fraschini Zeta RC25/60 was not intended to produce 1500hp, but 1250hp at 6000m, that's practically the same power than a DB605a at that altitude. After the first flight, of the F.6Z Ing. Fabrizi (Vizzola's chief designer) was pretty confident the residual cooling problems of the engine could be solved with a simple modification of the annular extractor at the end of the engine cowling, but the armistice blocked any evolution.
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You can thank the Regia Aeronautica decisions about engines. Traditionally Italian firms designed inline engines (both FIAT and Isotta Fraschini had built over 1000hp inline commercial aerial engines already in the '20s) but at the beginning of the '30s (exactly when DB, Rolls Royce and Allison started the development of the most famous inlines of WWII) the Regia decided to switch to radials, forcing the designers to work on a field they didn't know. They however managed to close the gap, and in 1939 was homologated the radial 1500hp Piaggio P.XII. A world class engine at the time. But at that point the Regia already decided to switch back to inlines, but they didn't want traditional V, only inverted V, so cutting off existing Isotta Fraschini engines and forcing FIAT to redesign the 1400hp A.38. That's why Alfa Romeo had to acquire the licence to produce the DB601.
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In reality it was an evolution of the Bf109 (that the Japanese had the occasion to examine), but the Japanese used many solutions that were also used on Macchi fighters (large landing gear, NACA five-digit airfoil, positioning of the weapons, positioning of the fuel tanks...) so it was visually much more similar to a Macchi C.202 than to a BF109. An example of convergent evolution. However, some particular (IE the quite complex positioning of the four fuel tanks, that's not obvious, and was identical in the Ki-61 and Macchi C.202) seems to indicate the Japanese had access to the Italian design as well.
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Simply to have tigher cowlings. If you see the engines, the blisters follow the bulges of the valve covers.
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For some obscure reason of any fighter engine usually is stated the emergency or takeoff power. For the FIAT A.74 is stated the normal power. The emergency power of the A.74 was 960hp, and it was pretty conservative, since the manual stated it could be mantained for half an hour. The difference between the 960hp of a FIAT A.74 and the 1200hp of a P&W R-1830 (that powered the first line of American fighters still in 1942), was that the P&W engines used 100 octane fuel. The Axis one had to use 87 octane one. More than engines, it was the Regia Aeronautica decisions about engines that "let their WWII aircraft down". Traditionally Italian firms designed inline engines (both FIAT and Isotta Fraschini had built over 1000hp commercial aerial engines already in the '20s) but at the beginning of the '30s (exactly when DB, Rolls Royce and Allison started the development of the most famous inlines of WWII) the Regia decided to switch to radials, forcing the designers to work on a field they didn't know. They however managed to close the gap, and in 1939 was homologated the radial 1500hp Piaggio P.XII. A world class engine at the time. But at that point the Regia already decided to switch back to inlines, but they didn't want traditional V, only inverted V, so cutting off existing Isotta Fraschini engines and forcing FIAT to redesign the 1400hp A.38. That's why Alfa Romeo had to acquire the licence to produce the DB601.
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@michaeltelson9798 Yet the same Gnome-Rohne wasn't able to evolve their design in something comparable to the P.XII (and later P.XV and P.XXII). The Italian tecnichans DID catch up in radial technology.
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You can thank the Regia Aeronautica decisions about engines. Traditionally Italian firms designed inline engines (both FIAT and Isotta Fraschini had built over 1000hp inline commercial aerial engines already in the '20s) but at the beginning of the '30s (exactly when DB, Rolls Royce and Allison started the development of the most famous inlines of WWII) the Regia decided to switch to radials, forcing the designers to work on a field they didn't know. They however managed to close the gap, and in 1939 was homologated the radial 1500hp Piaggio P.XII. A world class engine at the time. But at that point the Regia already decided to switch back to inlines, but they didn't want traditional V, only inverted V, so cutting off existing Isotta Fraschini engines and forcing FIAT to redesign the 1400hp A.38. That's why Alfa Romeo had to acquire the licence to produce the DB601.
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@chriscarbaugh3936 They required a lot of man hours to build compared to the 109 and stop. EVERY WWII fighter required a lot of man hours to build compared to the 109. Man-hours required to build Italian fighters were perfectly comparable to British and American fighters. IE, the FIAT G.55, costed 15.000 man/hours at the start of production, May 1943. It was planned to reduce it to 9000 man/hours with the 1000 sample and at a production rate of 200 samples/month. In Jan 1943, a P-47 costed 22.100 man/hours. In Jan 1944, 9.100 man/hours (at a production rate of over 500 samples/month). In Jan 1943, a P-38 costed 14.800 man/hours (less than the P-47, because it had been in production for more time). In Jan 1944, 9.600 man/hours.
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The Vigna di Valle museum of the Air Force, it's even free.
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Also the Japanese used the FIAT BR.20 bombers in 1938-1939. The Japs had several complains about the aircrafts (mostly range and defensive armament), but, curiously, none about the FIAT A.80 engines, that instead the Italians often considered problematic.
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