Italian air force is indifferent on on the air-cooled engines?

[Dogwalker]

I've been trying to understand the sorry state of Italian air force equipment in WWII and what were the factors behind it during the interwar years, and I came upon this interesting blog post that seems to answer it to a large extent: The Regia Aeronautica: Another Victim of Mussolini's Regime

This blog post places the blame largely on the poor industrial policy of the Mussolini regime, par for the course for fascist dictatorships one might even say. Mussolini was deathly afraid of labor unrest; indeed it was during fighting with communists during a previous period of labor unrest that he was able to gain power, so he was obviously afraid the same might happen to him. This resulted in very expensive and poor equipment, as there was no real competition, as the goal was more to keep the factory workers employed rather than selecting the best possible aircraft for the air force. The industry was organized in large vertically integrated conglomerates, with a strong incentive to use their own engines in their aircraft, rather than selecting the best available engine between multiple offers. And due to a policy of autarchy, there was essentially no competition from foreign suppliers either. Due to these factors, there was also little incentive for the industry to spend money on R&D; why bother when you had a guaranteed market anyway?

Considering this, my previous statement in this thread maybe needs some added nuance:


The above blog post makes the case that by the time this decision was made (1933) Italy was also behind in inline engines. So something drastic needed to be done anyway, and while I still think concentrating on one type of engine was the correct thing to do given the size of the Italian engine R&D ecosystem, perhaps which way the choice ultimately went wasn't fatal by itself.

So what should Italy have done, assuming we can ignore Il Duce's fear of labor unrest? Maybe opposite of what this thread ostensibly is about, that is, be even more prescriptive. Say,

1. The coin flip says to choose radials, as historically.
2. The state gives a "royal warrant" to two companies, saying all state aircraft must be powered by engines from these two companies. Two to ensure some competition between them. Shower them with R&D money to develop a couple of good engines each rather than a plethora of mediocre ones.
3. Split up the vertically integrated conglomerates, so that aircraft designers have an incentive to choose the best engine (from the above two companies) rather than being forced to use the in-house one.
4. State does aircraft tendering where the best offering is chosen.

The blog post seems really simplicistic.
This is an interesting overview of the Italian aeronautical industry from the origins to 1943 (in Italian, sorry). https://thesis.unipd.it/retrieve/28...277b907/Revisione_Tesi-definitiva_Novello.pdf
At p.59-60 you can see the expansion of the industry in the four years 1934-1938. The workforce expanded 472%, and the output even more than that. Expansions like that are rarely seen in any industry in peacetime. Simply Italy started from a relatively small base (total workforce was of 10073 people in 1934, and expanded to 47559 people in 1938), and there are limits to the speed an industry can expand (you need tooling, workshops, training...).
As for the Italian inlines having reached any tecnological limit in 1933, it seems more a statement of principles, than something substantiated by any data. It was because they didn't cast cylinder blocks? The casting of a basement was larger, and that of the cilinder heads were as large and more complex than that of a block of cylinders. There was nothing particularly difficult in casting cylinder blocks. The Fiat and Isotta Fraschini designers didn't do that because they still didn't feel the necessity to do that. And the IF Asso L.121 being still a good engine in the late '30s seems to give them reason.
Mind that, had Balbo really thought that Italian Inlines had reached a technological limit because the Italian firms didn't cast cylinder blocks, it would have been MUCH simpler to tell them the Regia Aeronautica would have accepted only inline engines with cast blocks of cylinders, than ditch inlines entirely and switch to radials.

 

[Shortround6]

Different countries had somewhat different limits.
US aircraft industry expanded at around 3X for several years until 1944 when they started to level off.
The US had large machine tool base which also expanded and the US machine tool base was also partially suppling Canada, Britian, and Russia.
What the US found was a problem was good managers. Helped by the US using management from the large auto industry and other domestic goods industries. By 1943/44 the US had a management shortage. Building huge factories and filling them with people was not giving the results expecting with poor management.

As for the Italian inlines having reached any tecnological limit in 1933, it seems more a statement of principles, than something substantiated by any data.

They aren't the only ones. US Navy pretty much refused to use liquid cooled engines during the 30s and 40s on principle. They bought a few prototypes to check if they were missing something. Too many navy pilots had to ditch due to Liberty engine failures in the 20s and when these junior pilots became senior officers their 'experience' over road and 'data' from the liquid cooled engine makers.
I have always found it interesting that several nations demanded air cooled engines for use in the desert to reduce water consumption. You need around 10 men per single engine aircraft (or how many men per truck?) and if each man needs 10 liters per day? Hopefully the liquid cooled engine was not leaking 10s of liters per day.
Technology was also part of this. For WW I and the 20s liquid cooled meant water. Glycol only started in the early 30s. Glycol permitted smaller radiators with less drag so the water vs air cooled difference wasn't a great. But once a 'regulation' was in place it took a lot to change it.

The casting of a basement was larger, and that of the cilinder heads were as large and more complex than that of a block of cylinders. There was nothing particularly difficult in casting cylinder blocks. The Fiat and Isotta Fraschini designers didn't do that because they still didn't feel the necessity to do that. And the IF Asso L.121 being still a good engine in the late '30s seems to give them reason.
Many of the cast block engines actually used a crankcase (basement?) for the crank and then used a combination cylinder block/head unit. Some did not. Getting a good seal on head and block was hard in combustion chamber area, especially with more supercharging raising cylinder pressures. Car style head gaskets often did not work in the 30s. The other thing is that separate cylinders had more flex than the one piece blocks and this became more important as cylinder pressures and higher rpm imposed higher loads. 3rd thing is that, depending on exact design, one piece (actually two on a V-12) had fewer cooling connections and/or less gasket area for less chance of leaks. One piece blocks also offered the opportunity of a slightly shorter engine and a slightly shorter engine offered slightly less weight and/or a stiffer crankshaft.

In the 20s and much of the 30s engine design was almost as much by intuition as by "knowledge". US engine designer Henry Miller (designer of what became Offenhauser engines) bankrupted a 1919-1921 car maker with one of his early designs. Got the vibration pattern wrong and they cracking/busting crankshafts all over the place in as little as 6 months.
Sometimes an engine company (designer) came up with a good engine but didn't know why it worked. So they only wanted to change things a little bit at time while they figured it out.

 

[Dogwalker]

Different countries had somewhat different limits.
US aircraft industry expanded at around 3X for several years until 1944 when they started to level off.
The US had large machine tool base which also expanded and the US machine tool base was also partially suppling Canada, Britian, and Russia.
What the US found was a problem was good managers. Helped by the US using management from the large auto industry and other domestic goods industries. By 1943/44 the US had a management shortage. Building huge factories and filling them with people was not giving the results expecting with poor management.

They aren't the only ones. US Navy pretty much refused to use liquid cooled engines during the 30s and 40s on principle. They bought a few prototypes to check if they were missing something. Too many navy pilots had to ditch due to Liberty engine failures in the 20s and when these junior pilots became senior officers their 'experience' over road and 'data' from the liquid cooled engine makers.
I have always found it interesting that several nations demanded air cooled engines for use in the desert to reduce water consumption. You need around 10 men per single engine aircraft (or how many men per truck?) and if each man needs 10 liters per day? Hopefully the liquid cooled engine was not leaking 10s of liters per day.
Technology was also part of this. For WW I and the 20s liquid cooled meant water. Glycol only started in the early 30s. Glycol permitted smaller radiators with less drag so the water vs air cooled difference wasn't a great. But once a 'regulation' was in place it took a lot to change it.

Mind that 1944 is wartime, when expenses are made without limits.
1934-1938 is, mostly, peacetime (for Italy there is the intervention in Spain and the Ethiopian war, but they are not comparable to WWII).

Yeah, in that same period, in Italian university engineering classrooms there were teachers that talked about the superiority of radial engines over inline ones. The decision of the Regia Aeronautica to switch to radials had not been taken in the void. But that has little to do with casting, or not, cylinder blocks.

It can be said that, at the start of the '30s, Italian inlines were slightly below the curve (The Allison V-1710 run for the first time in 1930, the Hispano-Suiza 12Y and DB600 in 1932, the RR Merlin in 1933, the Isotta Fraschini Asso XI in 1934), but it was surely easier to recover 1-2 years of development than starting from scratch with radials.

And, yes, it was a period of transformation, form the early engines designed by "intuition" to the later designed by technical knowledge. In Alfa Romeo, IE, this change came with the replacement of Vittorio Jano (the designer of the famous 8C competition cars and engines), that had not an engineering degree, was but someone that learned how to design engines "on the job", with Wilfredo Ricart, that was a trained engineer, in 1937.

Last. it was not like, in early '30s, Italian engineers didn't know what were the theoretical advantages of cylinder blocks. Fact is that, had they consider really necessary to use cylinder blocks, they could have done that. It was not an alien technology. Simply they felt that it was still not really neded. Their crankcases didnt' flex, their heads didn't leak. Their engines were not significantly longer or heavier. It's not the only case where, when someone introduces a new technology that has some advantage, someone else decides to stand with the old one, taking it to the extreme, and manages to stay competitive for years, or decades. OHV vs. OHC someone?

 

[Shortround6]

Mind that 1944 is wartime, when expenses are made without limits.

I could be wrong but P&W was having trouble finding good management for the Kansas City plant in 1943-44. Ford, Chevrolet and Nash (and Buick for R-1830s) were all licensed plants with their own management. But good management had been sucked into all war production, not just aircraft engines so there was no pool of management personal anymore to draw from. You can't even find tractor plant management or even plumbing fixture management (at least good ones).
Throwing money around doesn't solve the problem, it just makes it worse. Poor management is going waste money in terms of items produced, from airplanes to socks.

Yeah, in that same period, in Italian university engineering classrooms there were teachers that talked about the superiority of radial engines over inline ones. The decision of the Regia Aeronautica to switch to radials had not been taken in the void.

The early and mid 30s saw a lot of progress made just in drag alone with both liquid cooled and air cooled engines and the advantages were shifting back and forth. Things were moving quick and sometimes a company or country had to pick a side and stick with it rather than keep flip flopping. Things were not helped manufacturing wise with the advancement if fuel. 1930-33 you were lucky to get even 77 octane fuel. You can't use very much boost and you can't use high compression even with a very low boost supercharger. You are limited as to the amount of power you can make in on cylinder so that limits the power you can make in a V-12 compared to a 14 or 18 cylinder engine (also explains the W-18s).

It can be said that, at the start of the '30s, Italian inlines were slightly below the curve (The Allison V-1710 run for the first time in 1930, the Hispano-Suiza 12Y and DB600 in 1932, the RR Merlin in 1933, the Isotta Fraschini Asso XI in 1934)

You are mostly right . The Hispano was behind the curve and shows the problem if the Italians had stayed with the existing Italian inlines. Hispano pretty much just stuck a reduction gear on the front of one of their 1920s engines and added a small supercharger to back. As fuel got better the Hispano was not strong enough to either rev higher or to use much more boost. Granted in the 1930s (at least until 1935-36) there was not a lot money for new engines and keeping the R&D costs down seemed like a good idea. Allison was under-funded for many years. But the US might have gotten stuck with a 1933-34 engine instead of a 1939-40 engine?
There was a lot of things people were doing wrong in the 30s. It is not enough just to use 3 or 4 valves instead of 2. You need to get the fuel/air from the intake to the valves, lots of twists and turns and shape corners may cancel out a theoretical valve advantage. Lets also remember that WW I and the 1920s some people went to 3-4 valve heads as much to keep the valves from warping as they really did for better breathing. Exhaust design was also in its infancy. Get the exhaust out. don't let cold air back in so it warps the valves (main reason for short exhaust stacks) and at times, don't kill the pilot/crew/passengers with the fumes.

 

[Dogwalker]

The early and mid 30s saw a lot of progress made just in drag alone with both liquid cooled and air cooled engines and the advantages were shifting back and forth. Things were moving quick and sometimes a company or country had to pick a side and stick with it rather than keep flip flopping. Things were not helped manufacturing wise with the advancement if fuel. 1930-33 you were lucky to get even 77 octane fuel. You can't use very much boost and you can't use high compression even with a very low boost supercharger. You are limited as to the amount of power you can make in on cylinder so that limits the power you can make in a V-12 compared to a 14 or 18 cylinder engine (also explains the W-18s).

Sometimes you are lucky. The Merlin was a "plan B" of RR, that hat the financial power to pay for at least its initial development by itself, while the DB600 was a precise request of the German government. The teaching is that you need a plan B. If you put all of your cards on radials, because they seem to have a slight advantage now, and then you discover the inlines had recovered all the disadvantage and took the lead, and you have nothing there, its over. Engines are the technical bit in an aircraft that takes more time to be designed, refined and industrialized. The Regia Aeronautica did this mistake two times, first In the early '30, and then cancelling the Asso L.121 when Isotta Fraschini already had two development stage planned (L.122 and L.123).

You are mostly right . The Hispano was behind the curve and shows the problem if the Italians had stayed with the existing Italian inlines. Hispano pretty much just stuck a reduction gear on the front of one of their 1920s engines and added a small supercharger to back. As fuel got better the Hispano was not strong enough to either rev higher or to use much more boost. Granted in the 1930s (at least until 1935-36) there was not a lot money for new engines and keeping the R&D costs down seemed like a good idea. Allison was under-funded for many years. But the US might have gotten stuck with a 1933-34 engine instead of a 1939-40 engine?
There was a lot of things people were doing wrong in the 30s. It is not enough just to use 3 or 4 valves instead of 2. You need to get the fuel/air from the intake to the valves, lots of twists and turns and shape corners may cancel out a theoretical valve advantage. Lets also remember that WW I and the 1920s some people went to 3-4 valve heads as much to keep the valves from warping as they really did for better breathing. Exhaust design was also in its infancy. Get the exhaust out. don't let cold air back in so it warps the valves (main reason for short exhaust stacks) and at times, don't kill the pilot/crew/passengers with the fumes.

The Hispano 12Y was a good engine in the early '30, and a good base for further development. Then Hispano took a nap, and didn't develop it as others did with their engines, so it was slightly behind the curve at the end of the '30s, but, IE, the Soviets developed the design. It was the base for the Klimov M / VK series. (and yes, it looks primitive, but when your inline engine produces 1800 hp, you can stand whatever look it has) and, when Hisano woke up, of the 1800hp 12Z .

 

[tomo pauk]

It can be said that, at the start of the '30s, Italian inlines were slightly below the curve (The Allison V-1710 run for the first time in 1930, the Hispano-Suiza 12Y and DB600 in 1932, the RR Merlin in 1933, the Isotta Fraschini Asso XI in 1934), but it was surely easier to recover 1-2 years of development than starting from scratch with radials.

(my emphasis)
100% agreed.

The Hispano 12Y was a good engine in the early '30, and a good base for further development. Then Hispano took a nap, and didn't develop it as others did with their engines, so it was slightly behind the curve at the end of the '30s, but, IE, the Soviets developed the design. It was the base for the Klimov M / VK series. (and yes, it looks primitive, but when your inline engine produces 1800 hp, you can stand whatever look it has) and, when Hisano woke up, of the 1800hp 12Z .

1800 HP for the 12Z might've probably been found in a sales brochure? Reality seems to be 1500 HP.

 

[Dogwalker]

Just using the R-2800 as bench mark to show my line of thinking. An R-2800 might have been good for 1700hp with 87 octane?
It is why I didn't list power, Just displacement and RPM.

What did the Italians have to do to make their 18 cylinder engines work and what would it cost? Weight?

High octane Fuel.

For how much the R-2800 was clearly a more modern engine with much better development possibilities than, IE, the Piaggio 18 cylinders, technically they don't seem SO outclassed. At least in comparison with the R-2800 A and B series (the C is a complete redesign).

The P&W R-2800-1 flies for the first time in July 1939, producing 1,500 hp at 2,400 rpm at 2,300 m.
The P.XII RC.35 flies for the first time almost at the same time, producing 1500 hp at takeoff, and 1350 hp at 2050 rpm at 3500m.
They are not so distant. The difference is that P&W will make other 4 iterations of that engines before the first production model. Piaggio didn't have the money to do that. The model that was omologated in 1939 was already definitive. The first modification of the P.XII will be the P.XV.

The R-2800-5 (first production series) produced 1,850 hp at 2,600 rpm at only 820 m altitude.
The Piaggio P.XV RC.15/60 (improved P.XII that mantained same bore, stroke and so displacement) produced, it seems, 1600 hp at takeoff, and 1500 normal power at 6000m, it seems (informations are unfortunately scarce, even if the engine was ordered for serial production) at 2250rpm.
And that's obtained with, at best, 92 octane fuel, like the one used by the P.XIX (improved P.XI).
But, since the stroke of the P.XV cylinders was 13.4% longer than that of the R-2800, and so the average speed of the piston was higher by the same percentage for any given regime, RPM have to be increased by the same percentage to have comparable stress for the engine.
So, 2250rpm of the P.XV count as 2550 rpm for the R-2800. It's not so incredibly different than even the 2700 rpm of the late models (and that rating, for the P.XV was for the "normal" power, not emergency power).
Consider also that, since the P.XV and the R-2800 had the same bore, but the P.XV had longer stroke, to fill the cylinder of the P.XV, more air/gasoline mixture had to pass for the same area of the valve, and that requires more time.
Considering, IE, that the P.XIX, using 92 octane fuel, instead of 87 octane like the P.XI, had a 16% increase in power and 500m increased critical altitude at the same RPM, more than what the R-2800 could to with 87 octane, one has to wonder what the Piaggio radials could have done with 100/130.

 

[Shortround6]

one has to wonder what the Piaggio radials could have done with 100/130

Blown up?
Somewhat sarcastic but 100/130 fuel was not magic and many air-cooled engines were operating much closer to the edge than liquid cooled engines. Many (all?) could NOT make more power or not much by pouring 100/130 PN fuel into the tank and fooling around with the pressure limits like you could on liquid cooled engines.
Sticking with the R-2800 because in English it is much better documented.
The main changes on the R-2800 to go from 1850hp to 2000hp (at sea level or close) were changing to the oil scavenging system in the crankcase and increasing the rpm from 2600rpm to 2700rpm. Increasing rpm by 3.8% does not increase power by 8.1%. Perhaps there was a small boost in manifold pressure.
The R-2800 was rated at 2000hp with 100/100 fuel in 1941. It stayed at 2000hp with 100/125 and 100/130 fuel. It only was allowed to go higher than 2000hp when they used water-injection to help cool the engine. They were pouring about 1 gallon of water/alcohol into the engine per minute for cooling. At the same time they cut the fuel flow to the engine by about one gallon a minute. They had been using the extra fuel as coolant. The R-2800 in the A & B form had hit it's cooling limit. It needed more fins or longer fins or both, or it needed water injection.
Now it does turn out that the R-2800 could stand up to about 2600hp in the cylinders if given the right cooling from water injection, The crankcase, cylinders, pistons and so on were strong enough to stand up to the extra strain. The extra weight did not increase performance until they figured out how to keep the engine cool. many P-47 engines were converted in the field as were some F4U and F6F engines.
Maybe the R-2800 was overbuilt in 1940-41-42 and was heavier than it needed to be. But that also means that it had a longer overhaul live than some lower weight engines.

The Italians did not have those luxuries. Much Italian 87 octane was strange stuff compared to US 87 octane (or British 87 octane) and not much is written about it/them.
At least in the early/mid 30s the Italians were mixing in a fair amount of Benzine/Benzol into the base gasoline to raise the octane rating. All fuels of the time were rated at lean mixture.
Straight Benzol is better than straight run gasoline from an anti-knock point of view when running lean. It is around 150% better when running rich. Benzol does have a few problems, like freezing at 42 degrees F. and having about 10% fewer BTUs per pound/gal. But an engine running 20% or more Benzol rich is not running 87 octane fuel as we (Americans) think of it. British were also using a lot of aromatics (unspecified) in their "87 octane" so their fuel was not the same as US 87 octane. Italians and British were in the low 90s (?) compared to American fuel?

I will also note that the early B-26 manual (March 1942) calls for a max of 49in of manifold pressure in low gear (2600rpm) and a max of 40.5in in high gear. Misprint or cooling issues?
Note that the P-47 engines maxed out at about 52in in late 1943 using 100/130 fuel unless they were using water injection.
The Italian engineers were far from stupid and if they knew they would have access to better fuels they could have/would have designed the engines differently. But there are many things to take into account. Types of steels, heat treatment, ability to manufacture the desired fin shapes/density and many other things.

I will also note that the P&W superchargers do not appear to have been very good in the late 30s and first few years of the 40s. One reason that they went for the two stage superchargers
Unfortunately once you have spent several years going down one path it is hard to change paths.

 

[Dogwalker]

Blown up?
Somewhat sarcastic but 100/130 fuel was not magic .

It was not gunpowder either nor it was something unknown to the Italian Engineers, that they didn't know how to use. Simply they didn't have high octane fuel available for regular use in aviation.
What they did passing from 87 to 92 octane fuel from the P.XI to the P.XIX was passing from 1/6 to 1/7 compression ratio, and from 860 to 880 mmHg manifold pressure (500m higher, so they did some modification to the supercharger also), and that increased power 16%. What would have they done with 100 octane? More of the same probably. The engine would have exploded in one million pieces had they tried, because, casually, 92 octane and 1160 hp were the extreme limit of that engine? No. It would have melted for excessive heating? Likely not. The cowling of the P.XIX engined Re.2002 was even more closed than that of the Re.2000, and those of the P.XII were extremely closed. Likely exactly because those were not really compact engines. Having long stroke for your displacement means having more cooling surface for any given density of fins. One or two pieces would have required strenghtening? Maybe. That's what development is done of.

BTW the Italian nomenclature for the 92 octane was "benzina etilizzata", that means that, in respect to the 87 octane, the octane number had been increased by mixing it with ethanol.

Caproni Ca.169 with Piaggio P.XII engine.

 

[Shortround6]

A few things

Having long stroke for your displacement means having more cooling surface for any given density of fins.

But a long stroke means the 'extra' fins are in an area that needs the least amount of cooling. Cylinder barrel temperature varies considerably from the dead area down the base. Most aircraft engines try to have most of the actual combustion finished before the Piston is more the 20% of the way down the barrel. Time the piston in the lower 20% of stroke is a lot less with less time for heat transfer. Yes, some heat can travel down the barrel itself but a number of engines were several hundred degrees cooler at the base than at the head. A lot of engines used smaller fins near the base than at the top of the cylinder. You don't want too much variation in temperature in the barrel due to different expansion.

BTW the Italian nomenclature for the 92 octane was "benzina etilizzata", that means that, in respect to the 87 octane, the octane number had been increased by mixing it with ethanol.

The Italians were trying a number of things to try to get around the fuel problem. Ethanol is one work around. It is not a good solution for weak mixture, but it is a very good solution for rich mixture (Ethanol is rather wide ranged in its resistance to knocking/detonation). It also absorbs heat much better than gasoline per gallon and cools the intake charge.
However it has about 60% of the heating value (BTUs per gallon) of gasolene and is a bit heavier per gallon than gasoline. You are trading peak performance for range.
None of this stuff was easy and for nations that were poor in raw materials that had to do what they could.

The engine would have exploded in one million pieces had they tried, because, casually, 92 octane and 1160 hp were the extreme limit of that engine? No. It would have melted for excessive heating?

A question is how close were they coming. The Big Piaggio's were closer to the Wright R-3350 in cylinder size and the R-3350 is rather known for overheating, at least for most of WW II.
There were more than few radial engines that combined melting with exploding into at least a few large pieces. Not all cylinders detonate at the same time. Some planes have managed to land with one cylinder having launched itself though the cowl and into space (or atmosphere around the plane). I believe the test house at Bristol managed to launch a cylinder out of the test cell, through the roof of the building and into the car park next to the building.
It is not one or the other, it is sort of a combination, and you only need the weakest link in the chain (cylinder running hottest or leanest) for a catastrophic failure. Switching to liquid cooled engines. One "test" (combat area) of P-38 engines out of a number of engines (mid teens?) that made it back just about all of them failed in the same cylinder (no 5?) in the same cylinder bank. Try to figure that problem out with single engine planes?
Bristol thought they had radial engines figured out with the Hercules in 1938-39. God had other plans Bristol did get a lot more power from the engine, using several new cylinder designs and over 7 different cylinder head designs and ended with copper alloy heads for better cooling. And a Hercules cylinder head basically had to stay stuck the top of the cylinder as it's only job. The valves were down in the cylinder barrels.

 

[Dogwalker]

But a long stroke means the 'extra' fins are in an area that needs the least amount of cooling.

Since the hottest part is the more external part, the larger diameter engine has more area for cooling exactly where it's needed.

A question is how close were they coming. The Big Piaggio's were closer to the Wright R-3350 in cylinder size and the R-3350 is rather known for overheating, at least for most of WW II.

But not the Piaggio engines. Those were known to be "cold" engines. Hence the very closed cowlings. The Wright R-3350 could have been known for overheating, but at 2200 hp, not 1800, or 2000.

As for the Hercules, part of the problem of sleeve valves is that the sleeve/cylinder is not in direct contact with the finning, and that reduces the thermal exchange.

Cant Z.1018 with Piaggio P.XII engines.

 

[Airborne2001]

Even with the higher ups cancelling liquid cooled engine development for a bit, Fiat actually was on track to get a good engine under development as the A.38. The problem is that the Regia Aeronautica higher-ups insisted that the engine be inverted based on the DB 600, and this caused the A.38 to be redesigned into an unecessarily complex engine. The original design inspired by the AS.8 would've been less complex, and maybe could've been powering at least some aircraft before the armistice.

FIAT A.38, A.40, and A.44 Aircraft Engines

The last piston aircraft engines designed by FIAT were distinct and innovative. However, the V-16, X-24, and X-32 engines never entered production due to WWII and because existing engines proved su…

oldmachinepress.com

EDIT: Below I will attach a link from secretprojects.co.uk showing the evolution of the Fiat G.55, which in turn shows how the A.38 developed. I will also show a photo of the earliest G.55 design with the original A.38 design.

The road to G-55 (with the special participation of the CS-38)

Planning for a new fighter built around the new 1250 HP in-line liquid cooled FIAT engine (tendered to the 1938-39 competition for new engines and designated A.38) started immediately. The job was trusted to the II Design Office (Gabrielli) in Turin. First result was a somewhat P-40-like design...

www.secretprojects.co.uk