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Are there 2 different versions of the engine?
Because D.520Z with this engine achieved its top speed at 9150m with the engine doing 1300hp at 7500m
However D.524 and VG.39 are said to have this engine and yet their top speed is achieved only at 6000-7000m
another weird thing is how it has less horsepower at take off power at SL than its nominal power
I mean nominal vs take off at Sea LevelWith 1-speed superchargers, it is often the case that nominal power at altitude is greater than take-off power.
BTW - perhaps it might be a good idea to post the original table(s), so nothing could get lost in translation.
I mean nominal vs take off at Sea Level
I don't have the original table for that engineI'd really love to see the original table.
VG.39 did fly and achieved 625km/h at 5800mThe announced datas fot the Hispano-Suiza 12 Z were very changing between 1938 and 1946. In fact, this engine, with 1-speed or 2-speed supercharger, with carburetters or direct injection, never realised the anticipated performances.
The only "almost reliable" version was 12 Z-15 16 17 18. I gave their table recently.
The true story of this engine is still to be written !
I am not sure what the puzzle is about the engine making less power at sea level.
The Merlin III made 880hp at sea level and 1030hp at 16,250ft (4953 meters) with no ram on 87 octane fuel.
This was perfectly normal with single speed superchargers.
Chart is suspect as soon as it says WEP unless that is a translation error.
There is no reason the French would be using an American term/rating from 1942 in 1939/40.
There is also an obvious misprint/typo in the so called WEP manifold pressure sea level/take-off line. 1500mm hg really????
VG.39 did fly and achieved 625km/h at 5800m
View attachment 580083
Above, Arsenal VG-33; below Arsenal VG-39
The VG-39 engine is a problem for me.
The spacing of the exhaust pipes shows that it is indeed the 12 Z. But we also see that the air intake remained under the engine, so it is not a Planiol-Szydlowski supercharged 12Z, but one of the first models with an original Hispano-Suiza supercharger (the P / S had two lateral air intakes, the original HS only one lower – see VG 33 with its 12 Y-31).
There is therefore very little chance that the engine actually mounted on the VG-39 would have given the power and critical altitude indicated in the first message. And it is impossible to calculate any power curve interpolated from the 12 Z-17 I gave in another post, as the original HS supercharger lacked the « special » features of the P/S one, giving an almost « flat « curve from SL to critical altitude.
Note also the very thick traces of smoke along cowling and fuselage, showing how bad and rough the 12Z engine worked !
Ah ok but is there a chance D.524 had different supercharger than VG.39?Neither the D 524, the D/SE 520 Z, nor the M 520 T have ever flown.
It is a risky exercise to compare estimated data with actual data observed during flight tests !
And above all I do not see the purpose.
The additional intake pressure linked to RAM effect is very random, you can't give a general rule - the D 520 prototypes had problems with the design of air intakes, and on some production aircraft defectuous sealing of the intake circuit produced some critical altitude losses.
Finally, the greatest drag of the VG-39, assuming that it exists, can be explained by an increased mass (modified and larger wing with more armament) and a larger radiator.
Are there 2 different versions of the engine?
Because D.520Z with this engine achieved its top speed at 9150m with the engine doing 1300hp at 7500m
However D.524 and VG.39 are said to have this engine and yet their top speed is achieved only at 6000-7000m
This.All engines produced at that time were prototypes. ...
There is therefore a maximum chance that they have had different performances !