Advanced French Fighters vs 1942/1943 contemporaries (9 Viewers)

[Shortround6]

The situation of the G&R 14N is quite paradoxal, as owing to international tension, the French government had banned its export. Nevertheless, the engine was sold to some foreign countries, notably Yugoslavia to equip their Dornier 17: the first 20 airplanes were built with French engines, but the rest of the series received engines manufactured under license by IAM. Officially, these engines were 14K 32/33, but the pictures show that in reality they are 14N 10/11 (see finning density, or rocker arms lubrication circuit)...

I do not have your expertise.
I tend to lump all the late model G&R 14N and derivates together when judging for potential. Yes there some variations. But a 5-10% difference between the various countries is not enough to the turn the 14N (or clones/copies) into a world beating engine in 1942 and later. Even 1941 is doubtful.
The Soviets had the best resources and tried the hardest and got the M-88 with a 2 speed supercharger. Power was 1100-1150hp (?) which is not very different than the later 14Ns. although without altitudes it is tough to judge.
I will note that a P&W R-1830 with 100 octane and a two speed supercharger was good for 1050hp at 13200ft and weighed just under 1500lbs. Forget the 1200hp at sea level or close to it when comparing to the 14K and N.
The Soviet M-88B is supposed to have gotten 1100hp at 4000 meters and 1000hp at 6000 meters. Which is not bad and darn close to the what the R-1830 did with a two stage supercharger and at close to the same weight.

But for the G&R 14 to get much better it needs the center bearing and even more finning/cooling.

 

[Elan Vital]

But for the G&R 14 to get much better it needs the center bearing and even more finning/cooling.

Which are the main features of the GR 14R.

 

[bf109xxl]

The Soviets had the best resources and tried the hardest and got the M-88 with a 2 speed supercharger.

Could you please explain in detail what "the best resources" mean? A shortage of qualified personnel? Repeated changes of the chief designer? Repressions as well as the fear and nervousness caused by them?
In 1939 at plant No.29 in Zaporozhye, where the M-88 was produced, there was a shortage of about 3 thousand workers!!! In the same year there were 162 machine failures, the total downtime amounted to 108 thousand hours.

Power was 1100-1150hp (?) which is not very different than the later 14Ns. although without altitudes it is tough to judge.

It was achieved on serial engines rather in 1940 or even in 1941.

 

[Elan Vital]

Note that the 14M was still a very small engine, so the total power gains will still be on the small side. Need to make two of them per aircraft, while just one 14P or 14R will make an aircraft to do well, if not excellent.
The 14N with the better S/C would've also been interesting. Soviets managed to make the M88B (engine that traces the lineage to the 14K) do 1000 HP at 6 km, and 1100 HP at 4 km. Italians did the similar with the Piaggio P.XIX.

I originally believed the BMW 801 had a single-speed S/C, but it turns out it had two. Judging by the BMW-801D's figures on C-3 fuel and BMW-801C's takeoff output on 87 octane fuel, it seems that the 801 was more capable than the 14R of 1940 even accounting for the different displacement. However I don't have any power curves for the 1941 801C nor for the 1940 versions of the 801 in service or in development to have a better comparison.

The improved 14M (14S) seems like it would have been mostly important for extra durability rather than power, but it is mostly useful in the context of France operating aircrafts with it such as the Potez 63, the NC-600 and the Breguet 69X series. But the Potez was meant to be replaced by the Bloch 17X series and IIRC other models, the NC-600 had no guarantee of being ordered in large numbers, so that left the Breguet. So I'm not sure if there would be that many planes to use the 14S anyway.

This is assuming the Breguet assault bombers don't get the Breguet 700 treatment (normally meant only as a heavy fighter) and get the 14N/R family.

I agree about the S/C. Even if no reinforced variant of the 14N was made between the 14N-48/49 and the deployment of the 14R, an improved supercharger should IIRC still translate to:
- slightly increased shaft horsepower if a more efficient S/C with reduced power demand for the same capability is used (had the engine been strong enough, the extra efficiency would instead have been invested in more boost for the same power demand)
- the engine being able to maintain its maximum nominal power (so here around 1050 hp) or close to it at a greater range of altitudes. Per bretoal's article, the 14N-48/49 curve looked like this (red lines, dashed being the takeoff power):

It seems pretty clear that even if the engine was not made stronger at all and couldn't accept any greater max power, there was still substantial gaps that could be filled above 3700m (in reality more than that IIRC as these curves are for engines not on real aircrafts so without the effect of the airflow speed) and below it.

A 2-speed S/C would mean getting a second peak at a higher altitude and maintaining maybe over 900 hp well beyond the 4800m of the 48/49, and I guess being able to tune the 1st gear to further improve low altitude performance? The Szydlowski supercharger with swirl throttle mooted for the 14N would only have one speed if it was the 1939/40 type used in the HS-12Y engines, but the net effect would be a flatter curve below the rated altitude (eg more power down low) AND/OR the possibility of moving the curve towards higher altitudes, such that the gain at low altitudes is smaller but the gain at higher ones is significant. The gain certainly was massive between the Hispano-Suiza supercharger (save at low altitudes) when going to the Szydlowski, and even moreso in the variant used for the 12Y-49 engine which added up to 140 hp at higher altitudes compared to the 12Y-45.

It would be interesting if we could find a document confirming Gnome-Rhone's intention to implement such an intermediate change. The 14R was not going to appear for many months even if all went smoothly, and as such there would have been a need to improve performance in the meantime. The Bloch 155 otherwise would still have been stuck for over 6 months* with a severe disadvantage in the vertical field against the Bf-109s, while the Hispano-powered fighters would both get the 12Y-51, possibly some aerodynamic refinements already, and the 12Y-49-type S/C throughout the remainder of 1940 (which would translate to a 30+ kph speed advantage over the Bloch 155 per the figures we have). Luckily, the Bloch fighters had a fairly limited importance in the AdA anyway.

*That is unless the 550 kph target actually implied a "2nd-gen" Bloch 155 sometime in late 1940, rather than just a missed target for the entire 155 project.

The situation of the G&R 14N is quite paradoxal, as owing to international tension, the French government had banned its export. Nevertheless, the engine was sold to some foreign countries, notably Yugoslavia to equip their Dornier 17: the first 20 airplanes were built with French engines, but the rest of the series received engines manufactured under license by IAM. Officially, these engines were 14K 32/33, but the pictures show that in reality they are 14N 10/11 (see finning density, or rocker arms lubrication circuit)...

The case of other licensees is somewhat identical: it seems that they got around the export ban by continuing to "officially" manufacture 14Ks, but with some benefits from the latest developments designed in France for the 14N, which were essentially, as I said above, a finning reinforcement and a new lubrication circuit. See Walter "14K II".

In Italy, Piaggio used its own technologies from the beginning of its G&R licences : the 7K, 9K and 14K were deeply modified, particularly crankcases or downdraught (reverse) carburetor. The PVII (based on the G&R 7K), PIX (based on the 9K) and PXI (based on the 14K) versions will quickly receive improvements similar to the N series, and even, for the first two ones, a 2-speed supercharger that will always be missing from the French 14K or 14N.

Peyronnet de Torrès - see my published study - reports that the Piaggio PXI RC 72 (later improved to RC 100 /2v), engine of the Caproni 161 altitude record, was based on a Gnome & Rhône study which was never built, and named 14L.

Thank you. For a second I swear I saw a high figure of 1100-ish hp on the IAR K14 C32-1000A, but it's 1025hp so in line with the later 14N models. Apparently the Piaggio PXI did also have a 2-speed supercharger variant, the R.2.C.40?

 

[tomo pauk]

I originally believed the BMW 801 had a single-speed S/C, but it turns out it had two. Judging by the BMW-801D's figures on C-3 fuel and BMW-801C's takeoff output on 87 octane fuel, it seems that the 801 was more capable than the 14R of 1940 even accounting for the different displacement. However I don't have any power curves for the 1941 801C nor for the 1940 versions of the 801 in service or in development to have a better comparison.

You can take a peek here.

The improved 14M (14S) seems like it would have been mostly important for extra durability rather than power, but it is mostly useful in the context of France operating aircrafts with it such as the Potez 63, the NC-600 and the Breguet 69X series. But the Potez was meant to be replaced by the Bloch 17X series and IIRC other models, the NC-600 had no guarantee of being ordered in large numbers, so that left the Breguet. So I'm not sure if there would be that many planes to use the 14S anyway.

The earlier the French move on from the small radials idea, the better.

The 14R was not going to appear for many months even if all went smoothly, and as such there would have been a need to improve performance in the meantime.

IMO - the 14R was much more realistic thing in aggregate than expecting the S-P S/C appears on the 14N series if that idea was pushed some time in 1940. S-P have had probably their plate full with making enough of the S/Cs for the HS 12 engines; installing their S/C on the HS 12Y-51 would've netted a handsome improvement in overall power, and would've been far easier to do than having the same 'surgery' done for the 14N.
Perhaps retrofitting of the S/C from the 14R would've been a good idea?

 

[Bretoal2]

I originally believed the BMW 801 had a single-speed S/C, but it turns out it had two. Judging by the BMW-801D's figures on C-3 fuel and BMW-801C's takeoff output on 87 octane fuel, it seems that the 801 was more capable than the 14R of 1940 even accounting for the different displacement. However I don't have any power curves for the 1941 801C nor for the 1940 versions of the 801 in service or in development to have a better comparison.

The improved 14M (14S) seems like it would have been mostly important for extra durability rather than power, but it is mostly useful in the context of France operating aircrafts with it such as the Potez 63, the NC-600 and the Breguet 69X series. But the Potez was meant to be replaced by the Bloch 17X series and IIRC other models, the NC-600 had no guarantee of being ordered in large numbers, so that left the Breguet. So I'm not sure if there would be that many planes to use the 14S anyway.

This is assuming the Breguet assault bombers don't get the Breguet 700 treatment (normally meant only as a heavy fighter) and get the 14N/R family.

I agree about the S/C. Even if no reinforced variant of the 14N was made between the 14N-48/49 and the deployment of the 14R, an improved supercharger should IIRC still translate to:
- slightly increased shaft horsepower if a more efficient S/C with reduced power demand for the same capability is used (had the engine been strong enough, the extra efficiency would instead have been invested in more boost for the same power demand)
- the engine being able to maintain its maximum nominal power (so here around 1050 hp) or close to it at a greater range of altitudes. Per bretoal's article, the 14N-48/49 curve looked like this (red lines, dashed being the takeoff power):
View attachment 813949

It seems pretty clear that even if the engine was not made stronger at all and couldn't accept any greater max power, there was still substantial gaps that could be filled above 3700m (in reality more than that IIRC as these curves are for engines not on real aircrafts so without the effect of the airflow speed) and below it.

A 2-speed S/C would mean getting a second peak at a higher altitude and maintaining maybe over 900 hp well beyond the 4800m of the 48/49, and I guess being able to tune the 1st gear to further improve low altitude performance? The Szydlowski supercharger with swirl throttle mooted for the 14N would only have one speed if it was the 1939/40 type used in the HS-12Y engines, but the net effect would be a flatter curve below the rated altitude (eg more power down low) AND/OR the possibility of moving the curve towards higher altitudes, such that the gain at low altitudes is smaller but the gain at higher ones is significant. The gain certainly was massive between the Hispano-Suiza supercharger (save at low altitudes) when going to the Szydlowski, and even moreso in the variant used for the 12Y-49 engine which added up to 140 hp at higher altitudes compared to the 12Y-45.

It would be interesting if we could find a document confirming Gnome-Rhone's intention to implement such an intermediate change. The 14R was not going to appear for many months even if all went smoothly, and as such there would have been a need to improve performance in the meantime. The Bloch 155 otherwise would still have been stuck for over 6 months* with a severe disadvantage in the vertical field against the Bf-109s, while the Hispano-powered fighters would both get the 12Y-51, possibly some aerodynamic refinements already, and the 12Y-49-type S/C throughout the remainder of 1940 (which would translate to a 30+ kph speed advantage over the Bloch 155 per the figures we have). Luckily, the Bloch fighters had a fairly limited importance in the AdA anyway.

*That is unless the 550 kph target actually implied a "2nd-gen" Bloch 155 sometime in late 1940, rather than just a missed target for the entire 155 project.


Thank you. For a second I swear I saw a high figure of 1100-ish hp on the IAR K14 C32-1000A, but it's 1025hp so in line with the later 14N models. Apparently the Piaggio PXI did also have a 2-speed supercharger variant, the R.2.C.40?

I don't think that Gnome-Rhône planned any new developments for the 14N. In its latest versions (14N 20/21, 20/25, 38/39, 48/49) the engine was only a last resort obtained by grafting on the basic 14N, the highly finned cylinder heads of the 14P. It is obvious that from the moment the difficulties encountered with the 14P were overcome and this engine renamed 14R, the development efforts were focused on this range from which much better performances were expected for a size almost identical to that of the 14N - with, however, 200 kg more!

But only the engines of this line had the necessary characteristics to get safely more power:
- new crankshaft and connecting rods
- new crankcases
- another increase in the cylinder heads finned surface
- 2-speed S/C with (from the 14R 04/05) axial intake

The chronology is as follows:

- 14R 00/01 approved on April 26, 1939
- 14R 02/03 and 14R 04/05 presented on February 9, 1940.

By the beginning of 1940, the 14R 04/05 already had the performances of models developed after the war: i.e. 1590 hp at takeoff and 1580 hp in overboost (= military) at 5,000 m.

Everything therefore suggests that this engine would have superseded the 14N in a more or less short term (just as the 14N had replaced the 14K in 1937) if the 1940 collapse had not completely muddied the waters - the Germans having prohibited development and construction for 14R until they realized in 1943 that this engine was of some interest for their own aircrafts.

Moreover, if the engine was considered to be ready, its installation on aircraft still posed difficulties - see the oil emulsion/foaming problems which plagued the LeO 455 development.

Also, the Air Force had to manage its fleet and the manufacturers had to maintain their load plan....

 

[Bretoal2]

IMO - the 14R was much more realistic thing in aggregate than expecting the S-P S/C appears on the 14N series if that idea was pushed some time in 1940. S-P have had probably their plate full with making enough of the S/Cs for the HS 12 engines; installing their S/C on the HS 12Y-51 would've netted a handsome improvement in overall power, and would've been far easier to do than having the same 'surgery' done for the 14N.
Perhaps retrofitting of the S/C from the 14R would've been a good idea?

Two contracts had indeed been signed with Szydlowski in order to design S/C for 14M and 14N engines (May, 26, 1939).

For the 14R, this was of no interest since this engine's supercharger (in its second version with axial entry, from the 14R 04/05) had very high performances, with an efficiency close to 80%.

And do not forget that the Szydlowski S/C had a very particular flow/pressure curve and required a delicate adaptation of the carburetor.The system worked as if there were two throttles in the admission circuit, one in the S/C and one in the carburetor.

 

[tomo pauk]

wo contracts had indeed been signed with Szydlowski in order to design S/C for 14M and 14N engines (May, 26, 1939).

To the best of your knowledge, were such engines (14M and/or 14N + S-P S/C) at least tested on the test benches?

 

[Bretoal2]

To the best of your knowledge, were such engines (14M and/or 14N + S-P S/C) at least tested on the test benches?

No. There was not enough time for this to happen. But Joseph Szydlowski's biographer points out that in the engineer's private archives there are large study files corresponding to these contracts.

It would probably be very interesting to publish a summary of these works !

 

[tomo pauk]

But Joseph Szydlowski's biographer points out that in the engineer's private archives there are large study files corresponding to these contracts.

Very interesting.
Are these archives 'alive', free to access, etc?

 

[Bretoal2]

Very interesting.
Are these archives 'alive', free to access, etc?

I'm trying to get a contact at SAFRAN in Melun-Villaroche, but it is possible that the archives have remained in the formerTurbomeca headquarters in Tarbes. Both sites are identically far from my home - about 700 km....

 

[Shortround6]

Could you please explain in detail what "the best resources" mean? A shortage of qualified personnel? Repeated changes of the chief designer? Repressions as well as the fear and nervousness caused by them?

There were 8 countries/companies that made the G-R 14s under license or at least tried to develop it in any way?
Wiki says.
Among the licensees were
Industria Aeronautică Română in Romania,
Manfred Weiss in Hungary,
Alvis of the UK, ( actual manufacture is doubtful, at least more than 15. if that many)
Tumansky in the USSR,
Walter of Czechoslovakia,
Isotta Fraschini and
Piaggio in Italy.
Yugoslavia

So including France and ruling out some of the minor makers We have France (development stopped by war in 1940), Romania, Tumansky and Italy.
What-ever troubles the Soviets had developing the G-R engine (and there were a lot) Romania and Italy didn't have a lot for resources (trained man power, industrial base) either.
So out of the 4 best chances the G-R engine had the Soviets were the "best".
The French tries/prototypes of the 14R series show that the home factory thought that the 14K-N had reached it's limits.
There is only so much that can be changed on an old engine if you are trying to use old machinery (molds/jigs/fixtures) and if you are 'stuck' with the two bearing crankshaft there are very definite limits as to increases in RPM and/or increases in cylinder pressure you can use even if you figure out how to get a bit more cooling fin area onto the engine.
Allowing for shorter overhaul life only gets you so far.

The Soviets did not have the resources that the British and Americans had, but once the French were sidelined the Soviets had the best resources of the other makers of the G-R series of engines.

 

[bf109xxl]

Tumansky in the USSR,

There was no "Tumansky", there was a plant No.29 in Zaporozhye and there was a design bureau, which Tumansky headed for a short time in 1938-1940. Mastering and further development of the 14K line (M-85) began under the leadership of Nazarov (arrested in December 1937), and the finalization of the M-88 was completed under the leadership of Urmin. Also, a team from Klimov's design bureau worked there - the M-87A, apparently, can be considered to be their product.

What-ever troubles the Soviets had developing the G-R engine (and there were a lot) Romania and Italy didn't have a lot for resources (trained man power, industrial base) either.

Italy's technological level was much higher than the Soviet one at that time. As ridiculous as it may be, it is possible that it was easier to find enough qualified specialists and workers in Romania than in the USSR in the second half of the 1930s taking into account how many tasks the USSR had to accomplish simultaneously.

So out of the 4 best chances the G-R engine had the Soviets were the "best".

"The best" means developing an already obsolete and unreliable motor that was barely brought to an acceptable degree of reliability in 4 years? I agree with that wording.

The Soviets did not have the resources that the British and Americans had, but once the French were sidelined the Soviets had the best resources of the other makers of the G-R series of engines.

This is a common misconception of all those who try to extrapolate Western realities to the USSR of the 1930s. In the second half of the 1930s, the USSR went from being a beggar country to a poor one in comparison to West countries. And the main problem at that time was the lack of qualified personnel. Therefore, in this particular case it is quite possible that the Italians had more resources in reality.

 

[Bretoal2]

There were 8 countries/companies that made the G-R 14s under license or at least tried to develop it in any way?
Wiki says.
Among the licensees were
Industria Aeronautică Română in Romania,
Manfred Weiss in Hungary,
Alvis of the UK, ( actual manufacture is doubtful, at least more than 15. if that many)
Tumansky in the USSR,
Walter of Czechoslovakia,
Isotta Fraschini and
Piaggio in Italy.
Yugoslavia

So including France and ruling out some of the minor makers We have France (development stopped by war in 1940), Romania, Tumansky and Italy.
What-ever troubles the Soviets had developing the G-R engine (and there were a lot) Romania and Italy didn't have a lot for resources (trained man power, industrial base) either.
So out of the 4 best chances the G-R engine had the Soviets were the "best".
The French tries/prototypes of the 14R series show that the home factory thought that the 14K-N had reached it's limits.
There is only so much that can be changed on an old engine if you are trying to use old machinery (molds/jigs/fixtures) and if you are 'stuck' with the two bearing crankshaft there are very definite limits as to increases in RPM and/or increases in cylinder pressure you can use even if you figure out how to get a bit more cooling fin area onto the engine.
Allowing for shorter overhaul life only gets you so far.

The Soviets did not have the resources that the British and Americans had, but once the French were sidelined the Soviets had the best resources of the other makers of the G-R series of engines.

I don't know if the Soviets were "the best", even from your peculiar reading.

When Hispano-Suiza licensed the 12Y to the USSR, serious problems arose and, finally, it was decided to thicken the liners by 1 mm to prevent them from cracking.

As this extra thickness could be gained from the outside - the liner is screwed into the cylinder head and passes through the crankcase -, finally the bore was reduced from 150 to 148 mm.

This is well known... but cracking did not occur on the 12Ys licensed to Avia or Saurer, nor on the models manufactured in Spain.

Were the Soviets really the best?

 

[Shortround6]

I don't know if the Soviets were "the best", even from your peculiar reading.

It is simple, The Soviets managed to get the most power out of the 14K or K-M. Granted they had a bit more time than the French, except the French were shifting R & D over to the R.
The US and British weren't involved at all so we don't know what they could have done with it, if anything.
The Soviets built over 16,000 M-88s and production of all G-R based engines may have been well into the 20,000 range.
Romania built about 1000.
The Italians seem to have built quite a bit more than Romania, But not as much as the Soviets.
So where was the greatest R&D going on?
Who, aside from the French, had the biggest investment in plant (buildings, machinery, workers)?
Now if the Soviets weren't the "Best" where are the 14Ks or even 14Ns that could make the same power levels at the same altitudes? Maybe there are some certain models.

When Hispano-Suiza licensed the 12Y to the USSR, serious problems arose and, finally, it was decided to thicken the liners by 1 mm to prevent them from cracking.

There were problems during the first 100 hour test conducted in France, But nobody else was offering the Soviets anything better at the time.
The reduced bore was used on the M-103A in 1939? and how much power were the Soviets pulling from the engine at that time compared to what the French were getting out of production engines at the time? Now maybe Soviet steel and/or heat treatment wasn't as good. You do sometimes modify a design to take into account what you can actually make.

This is well known... but cracking did not occur on the 12Ys licensed to Avia or Saurer, nor on the models manufactured in Spain.

I don't think Avia made a 12Y much over 900hp? Warning, the power and altitude given by Wiki for the engines used in the IK-3 don't seem to line up with the published figures for the Hispano engines models listed.
Now if all you are trying to get out of engine is 860hp maybe you don't crack cylinders like you do when you use enough boost to get 1000hp out of the engine?
Soviets did manage to get over 1200hp out of the basic engine block/cylinders/crankshaft (different heads and valves) but they used better fuel and higher pressures. They also accepted shorter engine engine life which is part of it.
Saurer was rather low production and it took them several years (like 1943?) to get the later engines reliable.

This sort of side track from the G-N engine series.
The Soviets made among the highest power two bearing crankshaft models. They built them in very large numbers. The chances of getting more than a few % more out of the basic engine seems slim.


Now if so

 

[bf109xxl]

It is simple, The Soviets managed to get the most power out of the 14K or K-M.

They got not more than 1100hp in mass production, engine weight increased up to 685 kg.

Granted they had a bit more time than the French, except the French were shifting R & D over to the R.
The US and British weren't involved at all so we don't know what they could have done with it, if anything.
The Soviets built over 16,000 M-88s

~10,500 in seven years according to Kotelnikov.

and production of all G-R based engines may have been well into the 20,000 range.

16,000-17,000 in ten years. Not very impressive.

The Italians seem to have built quite a bit more than Romania, But not as much as the Soviets.

The question was about development resources, not mass production. There are different limiting factors there.

So where was the greatest R&D going on?

The question remains. Mass production is not a criterion of R&D quality. The USSR mass produced completely unfinished engines, which were not efficient despite their high characteristics.

Soviets did manage to get over 1200hp out of the basic engine block/cylinders/crankshaft (different heads and valves) but they used better fuel and higher pressures. They also accepted shorter engine engine life which is part of it.

The Soviets were never satisfied with the short lifetime of the engines and tried their best to increase it. This fact is very indicative in terms of R&D quality.

The Soviets made among the highest power two bearing crankshaft models.

What about the Piaggio P.XIX?

 

[Bretoal2]

What about the Piaggio P.XIX?

Unreliable.

An Italian copy of the Gnome et Rhône 18L, but G&R soon shifted, with the 18P and 18R, to a central-bearing crankshaft.

 

[bf109xxl]

Unreliable.

As well as the M-88.

An Italian copy of the Gnome et Rhône 18L

Could you please provide a reference? According to the most of available sources it was a 14K-based engine.

 

[Bretoal2]

As well as the M-88.

Could you please provide a reference? According to the most of available sources it was a 14K-based engine.

Sorry I confused the Piaggio PXIX with the PXII/PXXII.

The PXIX is just a slightly more advanced version of the previous 14 cylinders (same capacity, CR=7 with 92 octane petrol required, 940 mmHg boost). This allows for a few more hp, but the 2 bearings crankshaft concept is obviously at the end of its possibilities, a fact that the original designer Gnome-Rhône' had known since 1937.

 

[bf109xxl]

The PXIX is just a slightly more advanced version of the previous 14 cylinders (same capacity, CR=7 with 92 octane petrol required, 940 mmHg boost).

Exactly, but it reached 1150hp that exceed the power of the M-88B. According to Kotelnikov the Soviets reached 1250hp on the M-88F in 1943, however, the Soviets often confuse the power actually achieved with the power specified in the design assignment. And until I see the test report, I will continue to assume that the most powerful 14K was built by the Italians.

This allows for a few more hp, but the 2 bearings crankshaft concept is obviously at the end of its possibilities, a fact that the original designer Gnome-Rhône' had known since 1937.

This was obvious to many, including the Soviets - they were going to cease production of the M-88 in 1941. The only aircraft that required large quantities of M-88s was the DB-3(F), a rather mediocre bomber that could have been painlessly replaced by Bartini's DB-240 (Er-2). I will try to understand why this was not done - whether it was only due to Ilyushin's intrigues or whether there were quite rational motives.