Advanced French Fighters vs 1942/1943 contemporaries

[Bretoal2]

The 12Y-49 with the S-P supercharger was fitted to the D.520 Amélioré - a modified D.520 with some changes that were learned from the D.524 (These changes were planned to be made for all D.520-based platforms until the armistice stopped it from happening). The tests were later (1941), but it does give a pretty good indication as to how 520's fitted with the -49 would perform.
In the table I linked below, you can see that it was quite a significant boost to the base D.520 with the -45. It's just barely slower than the Bf 109 E-4/N at 570 kph / 354 mph compared to the E-4/N's 580 kph / 360 mph. That speed difference isn't huge, and becomes almost trivial when you remember that the D.520 was regularly able to outmanoeuvre the 109.
Rather than the Emils, the Friedrichs are the biggest concerns since those are much better performing and first show up in October. The D.525 and VG.35 with the -51 would be closer, but the F-1 is still a good bit ahead of both.

The improved D 520 (D520 amélioré) benefited above all from the tests carried out at the "Institut de mécanique des fluides de Banlèves".

Among the most significant elements, the fully faired landing gear housings and the oil radiator removed and replaced by a heat exchanger (on the engine's prestone circuit). And particular care given to the sealing of the intake air scoops - very important to recover a maximum of "ram effect". We can clearly see that the actual recovery altitude of the engine (6.900 m.) is well above that measured on bench.

The 12Y 49 differed from the -45 only by the S/C ratio, and many -45 engines were "retro-fitted" by simply changing the gears. The -49 was already in production at the end of 1939.

See here, note #9 on the left, on this 1939 document :

https://imagizer.imageshack.com/img923/237/6Eh2SM.jpg

We note in these same lists that the 12Y51 is planned with the pitiful home superchager !. With which the published performances are given. I do not know if the performances of the -51 with a P/S compressor have actually been established.

 

[TM06]

We note in these same lists that the 12Y51 is planned with the pitiful home compressor!. With which the published performances are given. I do not know if the performances of the -51 with a P/S compressor have actually been established.

I've been struggling to find a chart or something for the D.525, since that had the 12Y-51 and was fitted with the S-P supercharger - as opposed to the HS supercharger fitted on the D.523. However I know they exist somewhere.

 

[Bretoal2]

I've been struggling to find a chart or something for the D.525, since that had the 12Y-51 and was fitted with the S-P supercharger - as opposed to the HS supercharger fitted on the D.523. However I know they exist somewhere.

Do not forget that many data that circulated during the war, post-war and now again were simple calculations or forecasts of the design offices. It is sometimes very difficult to know if they really existed (see the legendary performances of the Bloch 157).

The S/P supercharger having married very well to the 12Y 31 (giving the 12Y 45 and 49), it was normal, I suppose, that some people thought of doing the same thing for the 12Y-51. But all the Hispano documents on the Safran site only speak of a "home" S/C for this engine.

If there is still something remaining for D 525, it may be in the Archives départementales de Haute-Garonne at Toulouse. They have the archives of the Dewoitine office.