Japanese Design Philosophy

[ThomasP]

We are hijacking the thread, but one more question - are you aware of any practical day-to-day reason why the people of Japan would prefer hydrogen to EV?

 

[Shinpachi]

Simply because Japan cannot produce oil and it is risky to rely on it from overseas forever.
Lithium is not only dangerous for the battery but also the resorce from overseas like oil.
The best choice is the hydrogen for Japan. This is what Japanese acknowledge well.

 

[ThomasP]

That makes sense. We (the US) have similar concerns re Lithium supplies. Otherwise, probably the most significant technical hydrogen vehicle problem for the US (I think) is how to store enough hydrogen in the vehicle to provide the perceived required drivable road range. Most Americans want a road range of at least 400-500 miles on a tank of gasoline.

 

[Shinpachi]

Japan is an island country, so Japanese do not have to immitate what the continent people do.
This is the lesson of ww2

 

[ThomasP]

Time for me to go to bed.

 

[SaparotRob]

Hydrogen gets a bad rep. Unlike fossil fuels, hydrogen blows up. Fossil fuels blow up, out and around. I guess they haven't figured out how to market safer explosions yet.

 

[Snautzer01]

Simply because Japan cannot produce oil and it is risky to rely on it from overseas forever.
Lithium is not only dangerous for the battery but also the resorce from overseas like oil.
The best choice is the hydrogen for Japan. This is what Japanese acknowledge well.

100 % right. Not only for Japan. The sooner the hydrogen fuel the better the world will get.

Cant by the life of me understand we change in Europa the dependency from oil states to the other that has a monopoly like China.
I really dont.
I also do not know why greenies push this scenario. Batteries are not green. And are finite in making because of materials used. Very poluting.
Better the Saoedi understand the have a sea of water, and more sunlight then others, and a deserts to win solar power from as nobody lives there. If they grasp that the money will flow, we have a clean fuel, they stay rich.
Give it some time.

 

[tomo pauk]

I maybe should have phrased it differently. It's that Japanese designs were simpler for the sake of less skilled workers, eschewing more intricate, and in some cases more sophisticated, technology in the process. Aircraft with liquid-cooled engines, such as the Ki-28 or the imported A7He, were rejected for their complex engines, among their other apparent deficiencies. Another example of a design rejected for its complexity was the Ki-94I.

Liquid cooled engines were probably not more complex that the 2-row radials?
Japanese manufactured and were using the Ki-61 and Ki-32, both powered by V12s. They also designed and manufactured complex 1-engined designs, including the carrier-capable aircraft and the aircraft to be operated from water. Number of designs were with sophisticated flaps and/or dive brakes.
Japanese deigns were far more complex that what Soviets made in 1941-45, let alone what the Italians made in 1941-43.

How about maximum (achievable) engine power, dash power, boost(?) or some other term I may be forgetting here?

I'd say that Japanese were specifying the max speed on the max power.

 

[Shortround6]

If you are deliberately using low powered engines you may have to stay with less powerful armament to keep performance in an acceptable area.

Where did the Japanese think differently?
The Ki-43 had about the least powerful armament of any fighter introduced in 1941.
The Zero used about the same armament as the Bf 109E of early 1940 did.
Ki-46 used crap armament for a twin engine fighter. And the list goes on................and on.................and on.
The late war Japanese Army fighter armament of two 12.7mm guns and two 20mm cannon was close in power to the American six .50 cal guns. The Japanese Army 12.7 gun about 3/4s the power of the American .50 cal and the Ho-5 cannon being about 2 1/3 times more powerful than the .50. The US .50 was a bit a better at deflection shooting and usually had more ammo.
The Ki-61 and Ki-100 put the 20mm guns in the fuselage and lost some effectiveness due to the lower rate of fire.

My point is, that from everything I've read online, in forum discussions and online encyclopaedias, the Ki-100 was, in essence, a slow P-51. Basically, Japanese aircraft were, in a sense, like uniquely slower variants of aircraft of other nations, which were not as slow.

The forum discussions and online encyclopedias are wrong.
The Ki-100 was a Ki-61 with an engine swap because the engines used in the later Ki-61s were both unreliable and no longer available due to a B-29 raid that heavily damaged the factory.
The Ki-100 was about as fast as a Ki-61 using the older Ha-40 engine (about 360mph at 5000mters) and being a bit lighter could climb a bit better. Slow sums it up rather well. Around 90mph slower even at 5000meters. At higher altitudes it gets worse. The climb isn't going to save the Ki-100.
The Ki-100 II with the turbo is a bit of phantom. Only 3 were built during the summer of 1945. Getting close to the performance of a 1943 P-51B/C isn't going to cut it. If the war had lasted longer (no A-bombs or other scenario) and had the Japanese actually been able to build few dozen Ki-100 IIs they could have wound up facing P-51Hs. Or F4U-4s/P-47Ns.

The problem was that the radial engine didn't really make enough power to overcome the drag, it came close and actually did better than the Ha-40 engine at higher altitudes. Higher is relative. The Ha-140 engine was pretty much a disaster. And does point out the problems with making engines that were too complicated. But perhaps for different reasons than some people think. One account claims that the Akashi plant making the Ha-140 engine was failing to met production quotas by a large margin due to problems casting cylinder blocks and crankcases. Compounded by about 50% of the completed engines failing to pass acceptance tests. You have to be able to build what you design. Something like 200 completed air frames were waiting for engines before the B-29 raid. Engineless planes on the ground do nothing for Japanese defense. Credit is due (a very large amount) to the Japanese that figured out the engine swap and did it so quickly and effectively. There was a 110 liter water/alcohol tank behind the pilots seat that may have improved performance over the "book' figures but with 1250hp at 6000 meters from the engine (without turbo) improvement in performance is not going to happen much over 20,000ft.

Basically the Ki-100 of the summer of 1945 was what the Japanese should have been building in the summer/fall of 1943.
It wasn't just the engines. In the summer of 1943 the Japanese were not building enough 12.7mm mgs and 20mm cannon.

 

[JoblinTheGoblin]

If you look at the pre-war evolution of the US. UK. German, and Japanese aircraft designs, it was fairly even across the board. In 1937 you could maybe say that Germany had the best fighter in the Bf109, in 1938 the US had the best [ insert here], the UK had the best [insert here], Japan had the best [insert here]. In 1939 the [insert here] had the best [insert here], etc.

I am mostly in agreement.

After 1939-40, the big change was the US and UK access to high quality 100/125 and 100/130 grade respectively. And they started to design their aircraft to use the fuel. Other than providing the same fuels to Japan, you would need to increase their population base, industrial base, and natural resource base, in order for the Japanese to do what the Western Allies did. One of the primary reasons that Japan and Germany went to war was to gain secure and ready access to strategic resources.

So in order to have the military aviation of another country such as the US, UK, or to a degree Germany, behave in a similar manner, you would remove access to high quality fuels, and reduce their population base, industrial base, and natural resource base.

Japan was not lacking in scientific, engineering, or military skills - they were lacking in resources to produce what was needed to fight a prolonged war.

I guess so. I mean, Germany managed to get rather dramatic performance gains with their fuel injection systems in aircraft like the Ta 152, though I've heard that German engines also suffered from problems with reliability similar to, if not greater than, those of higher power Japanese engines. From the criticism I've primarily heard in this forum of Soviet aircraft, their technological base was not much greater, but their aircraft seemed to have superior speed to equivalent Japanese 1800-2000HP engined aircraft like the J2M and Ki-84, if not exceeding the performance of Japanese aircraft with yet still more powerful engines (>2100HP) like the land-based, though heavily armed, A7M3-J Kai, albeit at the cost of armament, perhaps. I'm not entirely convinced that Japan, or another nation in its shoes, couldn't have done better with its aircraft, even with its own unique interests in mind. It's especially damning for Japanese aviation technology if what held back aircraft performance were minor issues like propeller lengths and pitch angles.

They also designed and manufactured complex...

Trustworthy online sources are not immediately accessible, but again, from what I've heard, designs such as the interwar liquid cooled engined Ki-12, and the late-war twin-boomed Ki-94I, were rejected based on their apparent complexity. Again, powerful engines such as the Mamoru and Homare suffered from constant issues with reliability that were never fully solved. Supposedly, the Japanese had trouble trying to grapple with the B-29's engine that they at some point managed to acquire an example of. The Kikka was designed with low skill labour in mind. These are some examples of the Japanese having difficulty working with complex designs, or rejecting or eschewing them outright based on potential difficulties. On a minor note, the Ki-84 and other similar Japanese aircraft were equipped with electric propellers (with low-voltage systems?) as opposed to an alternative technology like hydraulic propellers.

I'd say that Japanese were specifying the max speed on the max power.

Saburo Sakai claimed that the A6M2 had an "over-boost" speed of ~555 kph, greater than the official Japanese speed of about 515 kph. A 1944 intelligence document calculated a similar maximum speed for the "ZEKE Mark. 1", and even actual flight tests covered in that document yielded a figure of approximately 528 kph. That's only the Zero; other more advanced aircraft, like the Ki-84 and N1K2-J, also have varying speed figures, apparently because of their unreliable engines having to be de-rated for testing. The Ki-84's 624 kph speed was achieved with a Ha-45 with lower boost than normal, and differing figures of 631 kph, 634 kph, and an anecdotal 660 kph have been given. The N1K2-J's 596 kph figure was also achieved with a reduced power engine, and I've heard a ~620 kph figure listed as its top speed somewhere on this forum. Both aircraft, and their respective performances, have been the subject of much discussion on this forum, but I digress. You should see my point here.

The Ki-43 had about the least powerful armament of any fighter introduced in 1941.
The Zero used about the same armament as the Bf 109E of early 1940 did.
Ki-46 used crap armament for a twin engine fighter. And the list goes on................and on.................and on.
The late war Japanese Army fighter armament of two 12.7mm guns and two 20mm cannon was close in power to the American six .50 cal guns...

I was thinking moreso of Soviet aircraft and their armament, early to mid-war. To add, the Ki-46 was designed as a high-speed reconnaissance aircraft, and was forced into an interception role against the B-29 threat later in the war. Late-war Japanese prototypes, such as the J7W and Ki-83, were equipped with heavier 30mm cannons.

The forum discussions and online encyclopedias are wrong.

I'll throw them a bone and add '...at lower altitudes'.

Basically the Ki-100 of the summer of 1945 was what the Japanese should have been building in the summer/fall of 1943.

I don't disagree.

Edit: At a glance, the Ki-83 appears to be suspiciously slower than the similarly large and powerful F7F, which even has greater wing area. Yet another example of Japanese aerodynamic weirdness.

 

[SaparotRob]

Anybody else here converting those numbers into Freedom Units?

 

[Shortround6]

I was thinking moreso of Soviet aircraft and their armament, early to mid-war. To add, the Ki-46 was designed as a high-speed reconnaissance aircraft, and was forced into an interception role against the B-29 threat later in the war. Late-war Japanese prototypes, such as the J7W and Ki-83, were equipped with heavier 30mm cannons.

The Soviets used the most powerful for installed weight of any WW II aircraft guns. A single Soviet 12.7mm mg and single 20mm cannon are well under what the Soviets wanted to use but compared to the Japanese the Soviet 12.7mm gun was around twice as powerful compared to the 12.7mm Ho-103. The Japanese Ho-5 cannon was about 70% as powerful as the ShVAK cannon. A Soviet fighter with a single 12.7mm and a 20mm in the prop was about as powerful as a Japanese fighter with two 20mm Ho-5 cannon.
Japanese wanted a lot of things in 1944-45 but it was too late. IJA 30mm gun would have been useful but...............Fired a lighter shell than the German MK 108, fired about 2/3rds as fast. Didn't have a mine shell.

My error on the Ki-46. I was thinking of the Ki-45, the twin engine fighter, not recon plane and the Ki-45 had pretty crappy armament for a twin engine fighter.

I'll throw them a bone and add '...at lower altitudes'.

A lot remains to be discovered about actual performance of Japanese WW II aircraft. However the Ki-61 with the older Ha-40 engine was supposed to be good for 302mph at sea level.
The Ki-100 was supposed to be good for 317mph at 1000meters. I have no idea if they were both using T-O power or something less (or for the Ki-100 something using water injection).
The Engine in the Ki-100 was rated at 1500hp at 2600rpm for take-off and 1350hp at 2500rpm at 2000 meters in low gear. 1250hp at 5800meters.
The engine in the Ki-61 was rated at 1175hp for take-off and 1100hp at 4200 meters.
The Ki-61 was supposed to climb to 5000meters in 7 minutes and the Ki-100 was supposed to need 6.0 minutes.
P-51B in June of 1943 is supposed to have needed 5.1 minutes to climb 17,400ft using 60.5 in of boost (15lbs) and most likely the V-1650-3 engine. Later rated for 67in (18lbs).

The Ki-100 did have more power, but not quite difference that the take-off power indicates. The Ki-100 did have better performance but not that much better for being over 1 1/2 years later. It may have been much more reliable which may have given the pilots more confidence.

Edit: At a glance, the Ki-83 appears to be suspiciously slower than the similarly large and powerful F7F, which even has greater wing area. Yet another example of Japanese aerodynamic weirdness.

There is a lot that is suspicious about the Ki-83, or about many of the late war Japanese aircraft and engines in general. Not picking on the Ki-83 in particular.
My suspicion is that that the later Japanese engines never came close to the "rated power" listed for them, at least in flight. Now you might be able to do a lot by accepting short engine life.....But?
The engines in the Ki-83 were supposed to be 90.8% the displacement of the engines in the F7F and turn just 3.6% faster. Use worse fuel. be about 4.5 (114mm) smaller in diameter and weigh 91.6 as much. And use 350mm of boost (?) which around 1.46Ata or 44in or under 7lbs of boost?

Now peak power could very well rely on water injection to get around the low octane gas the stated boost may not be taking that into account but getting the same or more power out of engine that is not running fast enough to compensate for the smaller size or using enough boost (in the figures we have) to compensate does look suspicious.

 

[Admiral Beez]

- Smaller, weaker, but simpler and lighter engines.

I think Japan was forced to adhere to lightly constructed, protected and armed fighters because they did not have access to powerful engines. Once Japan had powerful engines they moved to fighters with armour, self sealing tanks and heavier armament, such as the 2,000 hp Nakajima Ki-84.

 

[yulzari]

Anybody else here converting those numbers into Freedom Units?

Imperial dear boy.Imperial.

 

[tomo pauk]

Trustworthy online sources are not immediately accessible, but again, from what I've heard, designs such as the interwar liquid cooled engined Ki-12, and the late-war twin-boomed Ki-94I, were rejected based on their apparent complexity. Again, powerful engines such as the Mamoru and Homare suffered from constant issues with reliability that were never fully solved. Supposedly, the Japanese had trouble trying to grapple with the B-29's engine that they at some point managed to acquire an example of. The Kikka was designed with low skill labour in mind. These are some examples of the Japanese having difficulty working with complex designs, or rejecting or eschewing them outright based on potential difficulties. On a minor note, the Ki-84 and other similar Japanese aircraft were equipped with electric propellers (with low-voltage systems?) as opposed to an alternative technology like hydraulic propellers.

You can compare Soviet, British and German engines and designs in 1941-45 and see who was making, in series, the more complex stuff. Especially, check out how the European countries were faring with complex engines (ie. more than 12-14 cylinders) vs. what Japanese were making. Japanese 4-engined designs vs. Soviet or German 4-engined A/C? Japanese carrier-borne A/C vs. European carrier-borne A/C?
Yes, Japanese series production was not on par what Europeans did, but still.

Or, compare what Japan was doing in 1941-43 vs. Italy in the same era (Italy was with even more serious problems in making the good stuff, abd in making a lot of stuff).

FWIW, Americans have had no problem with Homare in tests - perhaps because their 91 oct fuel was actually 91 oct fuel?

Saburo Sakai claimed that the A6M2 had an "over-boost" speed of ~555 kph, greater than the official Japanese speed of about 515 kph. A 1944 intelligence document calculated a similar maximum speed for the "ZEKE Mark. 1", and even actual flight tests covered in that document yielded a figure of approximately 528 kph. That's only the Zero;

Claims of servicemen, that most were honorable men, take second place when we have test figures. Test figures for the A6M2 note a bit over 330 mph, eg. here.
Over-boosting the engine on 91-91 oct fuel is not going to yield the same extra boost as it was the case when over-boosting was done with 100 oct, let alone with 100/130 grade fuel; lowe extra boost = a small gain in power = even smaller gain in speed.

other more advanced aircraft, like the Ki-84 and N1K2-J, also have varying speed figures, apparently because of their unreliable engines having to be de-rated for testing. The Ki-84's 624 kph speed was achieved with a Ha-45 with lower boost than normal, and differing figures of 631 kph, 634 kph, and an anecdotal 660 kph have been given. The N1K2-J's 596 kph figure was also achieved with a reduced power engine, and I've heard a ~620 kph figure listed as its top speed somewhere on this forum. Both aircraft, and their respective performances, have been the subject of much discussion on this forum, but I digress. You should see my point here.

Max power of 'established' engines is one thing; restricted power of newer engines, like the Homare family, is another.
I have no problems in accepting that, with a fully-rated Homare, the Ki-84 would've been making ~650 km/h, and the N1K2 a tad less.

 

[Shortround6]

Flying captured aircraft with different fuel might go easy and it might go hard.
Or even allied fuel.
Most fuel was about 18,700 BTUs per pound (or equivalent) but it might vary (mostly lower) by a few hundred.
The only ways to get more power is to over rev or over boost. But you can only over boost at altitudes where the supercharger can provide more air.

A lot of the anti-knock compounds had less BTUs per pound than gasoline and for the allies that often meant that 100/130 was as high as they could go without getting less range (more fuel burned per hour in cruise). What the Japanese wound up with is certainly subject to question.
The allies had trouble in 1942/43 just trying to make enough 100/130 and they had to go from 3cc of lead to 4 cc(?) and then to 4.6cc. Some spark plugs and engines got along pretty good and others would only run right (after a few hours) with certain brands/types of plugs. There was not a 100% certainty that just because Engine A liked spark plug WWW that Engine B would like it too. They often had to run the engines for a minute or two at high power in the middle of cruising to clear the plugs. Now Plugs can both oil foul and lead foul AND foul from additives that were supposed to keep the lead from sticking to the valves and valve seats.
Put some 100/130 into axis aircraft and you may be able to use more boost and get more power. Using the same boost should give the same power. 100/130 fuel in an engine that was supposed to run on 91 octane didn't do anything, except perhaps foul the plugs quicker.

Poor storage might degrade fuel at front line airfields. Extremes of heat or cold. Getting fresh or at least good condition spark plugs might have been hard. Making sure the wiring harness was up to spec is also a problem. Please note that at times new US aircraft had problems at high altitude with wiring harnesses and or cross firing in the magnetos. US resorted to pressurizing the magnetos on some high altitude aircraft. What was going on in planes that were picked up on forward airfields with not the best support?

Japanese engines are puzzle as they seem to have gotten a lot out them.
Maybe the US was doing something wrong?
R-2800 was 28% larger than the Homare, ran about 11% slower, used less compression, but used a bit more boost (or a lot?) 52in is about 1320mm of hg and the later Homare was supposed to use what for take-off? Use of a lot of water injection?
Homare was getting almost as power at 6400meters with a single stage supercharger as the R-2800 in the Corsair was using a two stage supercharger, and using less manifold pressure to do it? And using an engine that was only 72% as heavy?
Using 3000rpm for a 150mm stroke is just about the limit even for a V-12 although it may be OK for short service life (different for short term power).
The light weight is also questionable although again, short life may let them get away with it.

 

[NevadaK]

I'm not sure if this answers the OP's post, but my feeling is that the Japanese had some very good aircraft designers that were limited by resources overall and power plants in particular. Engine development in Japan strikes me as being similar to Germany in the desire to develop smaller displacement engines with very optimist power outputs. The failure to meet design objectives meant that Japanese aircraft performance was unable to keep up with newer US/UK aircraft. My two cents.

 

[tomo pauk]

Japanese engines are puzzle as they seem to have gotten a lot out them.
Maybe the US was doing something wrong?
R-2800 was 28% larger than the Homare, ran about 11% slower, used less compression, but used a bit more boost (or a lot?) 52in is about 1320mm of hg and the later Homare was supposed to use what for take-off? Use of a lot of water injection?
Homare was getting almost as power at 6400meters with a single stage supercharger as the R-2800 in the Corsair was using a two stage supercharger, and using less manifold pressure to do it? And using an engine that was only 72% as heavy?
Using 3000rpm for a 150mm stroke is just about the limit even for a V-12 although it may be OK for short service life (different for short term power).
The light weight is also questionable although again, short life may let them get away with it.

Japanese engines were getting pretty good power/weight ratios as a rule, Homare is nothing out the ordinary for them. The feather-weight Kinsei 60s were making 1600-ish HP with water injection, for example; the Ha 109 was also very light for a 1500 HP engine on 91-92 oct fuel and no ADI.
Later in the war, effect of direct and indirect Allied 'brake' to the supply of the raw materials (nickel, chromium, tungsten etc.) + bombing + suspicious octane rating of the fuel (91-92 oct was the 'book' value, the actual oct value was ??) + dubious supply of spare parts = it will be a miracle if the book values were obtained in everyday service.
Homare was noted as 'new tech' engine, perhaps the 'old-tech' 18 cyl Ha 104 was less susceptible to the glitches, while weighting 25% more - sometimes going conservative has it's appeal.

Western engines, like the R-2800 or BMW 801, might've been over-built? Nothing wrong with that, but it might result in the over-weight an/or over-sized fighters. The 2-stage B-series R-2800s were with small impellers, that were also not refined (the straight vanes, instead of the curved ones), so it might be argued that a more refined and big impeller on the Homare was as good as it gets.

 

[Shortround6]

I'm not sure if this answers the OP's post, but my feeling is that the Japanese had some very good aircraft designers that were limited by resources overall and power plants in particular.

It seems that the Japanese took quite some time to build 2 speed superchargers. Most don't seem to show up until 1942 ? Granted one or two showed up in limited aircraft earlier.
Armstrong Siddely marketed the the first engine with two speed supercharger but the engine was pretty much trash so maybe it didn't get the notice it might have?
However by 1938 (or the fall of 1938) Bristol was pushing the two speed Pegasus, RR had the two Speed Merlin X engine, Wright was offering 2 speed R-1820s and even retro fit kits (?)
The Jumo 210 had a two speed supercharger.
By 1940 the Soviets were building two speed superchargers on the M-105s and on the M-88 radials and planning them on the newer engines.
P&W had skipped the two speed in 1938-39 and worked in the two stage supercharger on the R-1830 but in 1940 they back tracked and offered a two speed single stage engine.
The French didn't get anything into production but they were planning on either a 2 speed or variable inlet one speed depending on brand of engine.
Not sure if/when the Italians did anything.

It does seem that the Japanese, once they decided to use two speed superchargers, made rather good ones. And/or with the lower octane fuel they equaled what some of the allied engines would have done with lower octane fuel. The two speed Sakae engines were good for 980hp at 6000meters. A two speed R-1830 was only good for 1050hp at 13,100ft (just under 4000meters) an R-1830 operating at 6000 meters would be done to just over 900hp?
Japanese problem was they were introducing the the 2 speed Sakae into service squadrons (JAAF) in Dec 1942/Jan-Feb 1943 And the US Navy was building F4Us and F6Fs and the Army was introducing P-40Fs, Ks, M, and Ns and P-38Gs are coming off the production lines.

How much was too much duplication of effort I don't know. I would note the P&W spent a lot of time developing only a very few engines during the war. They concentrated on the R-2800 and the R-1830 only got some trickle down stuff late in the war. The R-2000 was shoved onto the shelf as a "better" R-1830 for transport aircraft and there it stayed.
The R-4360 28 cylinder used R-2800 cylinders, heads (basic design) pistons and rods (mostly) and the end war R-2180 was 1/2 of a R-4360.
That was P&W R&D in nutshell. No jets, liquid cooled sleeve valve engines were canned in the fall of 1940.
The small 9 cylinder trainer engines may have gotten better materials/inspection but they ended the war at the same power levels they started with.

Now there was a lot of development at P&W to go from an 1850hp R-2800 engine in 1940 to a 2800hp R-2800 in late 1944/early 1945 and increase the service life at the same time.
But they didn't go off on wild goose chases.

 

[tomo pauk]

However by 1938 (or the fall of 1938) Bristol was pushing the two speed Pegasus, RR had the two Speed Merlin X engine, Wright was offering 2 speed R-1820s and even retro fit kits (?)
The Jumo 210 had a two speed supercharger.
By 1940 the Soviets were building two speed superchargers on the M-105s and on the M-88 radials and planning them on the newer engines.

I'd say that the Merlin X in 1938, as well as the 1940-vintage M-105 and M-88 with 2-speed S/C were very, very rare engine types.

The French didn't get anything into production but they were planning on either a 2 speed or variable inlet one speed depending on brand of engine.
Not sure if/when the Italians did anything.

Italians were certainly behind the curve, about the only non-1-speed S/Ced engine were of the German origin,
French were not just planing on the variable inlet, they put it in production and in service. Yes, their (G&R's) 2-speed S/C was too late for ww2.