Jack vs. Tojo - Which was better? Why?

[AerialTorpedoDude69]

Lots of great comments here, sorry to only address a few.

The simplest, though not the only, explanation for the greater number og Ki-44's, is that it was earlier, being in production before Pearl Harbour and entering (limited) service shortly after. The J2M was at least a year behind, and then the innovative features caused teething troubles. The Ki-84 and the N1K1-J may be said to be contemporary, so both interceptors had a more all round alternative ready at about the same time. Which one of those that were the most complex I can't say, they both had their share of problems.

I have to point out that Ki-44 production also terminated at the end of 1944 and had been slowed since early 1944. On the other hand, Raiden production, which had never been more than a trickle, reached their peak in June of 1944. But even at the peak of Raiden production, almost twice as many Ki-44s were being made. So even with huge demand for Raidens, and Ki-44s being phased out, more Ki-44s were being manufacturered.

IIRC, Allied bombers didn't begin hitting Mitsubishi factories and sub manufacturers until December of 1944. So the reason for Mitsubishi's inability to make more Raidens was (just as you say) multifold. Chief among these factors was the supply shortage caused by Allied raids on Japanese shipping. And the supply shortage is what led to greater emphasis on a cheaper fighter. Something that Japanese war planners had foreseen during the development of the Zero. An island nation that was dependent on imports would have to build cheaper, lighter aircraft if there were ever a disruption of the supply chain.

However, another major reason was that the Raiden and Ki-44 were designed for different purposes. The Ki-44 was designed with the ground war in China in mind. In fact, almost all Ki-44s were sent to Indo-China. The Navy, on the other hand, was still primarily engaged in combat that involved extremely long ranges and therefore a fighter like the Raiden wasn't in demand until Allied bombers were flying with impunity over Japan in the Summer of 1944. There were likely Ki-44s stationed in Northern Japan as well in order to protect against the Kuril and Hokkaido raids, but I know very little about this part of the war.

But more or less, I think you and Tomo are right that price alone wasn't a determining factor, but rather just one factor among many.

I agree with Just Schmidt - the Ki-44 was manufactured in much greater quantities because it's production started much earlier vs. how the war was long.
J2M cost to produce was probably lower than of the Ki-84 that used 18 cylinder engine, and certainly lower than the Ki-45 or J1N that were with two engines.

See above for the production numbers relative to Japanese production capabilities.

Unfortunately, I don't know how much the Kasei 23a production cost versus the Homare 21, but they weighed about the same and the 23a's fuel injection system was undoubtedly more complicated and expensive than a carb system (although the bowl-prime on the Homare 21 was regarded as having elements of a direct injection system). Maybe the Homare required more man-hours to produce, but it couldn't have been much more. Otherwise, the Ki-84's total manufacturing costs were supposedly almost half that of a Ki-44 or Ki-43 (IIRC, this is according to Richard Bueschel's book), which themselves were fairly cheap aircraft from a materials standpoint but required massive amounts of manpower to produce, as with all Japanese aircraft.

Keep in mind that a P-51 was like 2,000 man hours and a Spitfire was around 13,000 man hours. While there are no man-hour or cost numbers for a Raiden, we can guess that it was more complicated to build than a Zero based on its weight, extension shaft, and laminar wing. Also, to bolster your point, the Ki-61 had to have been one of the most expensive Japanese aircraft of the war given its weight, its high aspect wing, the absurdedly robust diving speed, and other advanced features and yet the Japanese built around 3,000 of them. Perhaps the Army's military planners were more likely to adopt expensive aircraft given that they didn't have to launch aircraft from carriers?

I can see that my thinking is overly reductionist in this regard. You are right that there is more complexity to Japan's aircraft design paradigm than just cost. Though, I do have some questions about the Ki-61. Like, why? The Ki-44 was available earlier and offered similar performance. It just didn't make sense to make the Ki-61. And on top of that, the Japanese had already added MW50 to a DB601A. The Ki-61 just seemed like too much effort for very little advantage over the Ki-44. And on top of that, the Ki-61 could have been a much better plane with just a little more effort and expense. But that is a conversation for a separate thread.

 

[special ed]

Since Imperial Japan was a maritime empire, it makes sense that they would have floatplane fighter designs early on.

The A6M2-N and N1K1 enabled them the ability to station and operate fighters in remote areas, often times just a protected lagoon.

Of course, as the fortunes of war turned against the Empire, floatplane operations were at risk and the need no longer existed, except for the M6A1, which was designed to operate from carrier subs.

Exactly why floatplane fighters were need in the early years. The Japanese plan was to take as many islands as possible, however the terrain was not always good for building an airstrip. Float fighters, docked at the piers where the supply barges would unload, could easily drive away the PBY recon. As the US took islands with airstrip possibilities, the floatplane became a disadvantage against land based fighters flying within patrol range.

 

[GrauGeist]

Exactly why floatplane fighters were need in the early years. The Japanese plan was to take as many islands as possible, however the terrain was not always good for building an airstrip. Float fighters, docked at the piers where the supply barges would unload, could easily drive away the PBY recon. As the US took islands with airstrip possibilities, the floatplane became a disadvantage against land based fighters flying within patrol range.

The USN's F4F-3S was developed for the very same reason: deploying to foreward areas that were unimproved. Much like it's Japanese counterparts, the F4F-3S suffered performance penalties due to the floats and only one was made.
The USAAF also considered a P-38E floatplane, but it was never developed.

 

[tomo pauk]

Otherwise, the Ki-84's total manufacturing costs were supposedly almost half that of a Ki-44 or Ki-43 (IIRC, this is according to Richard Bueschel's book), which themselves were fairly cheap aircraft from a materials standpoint but required massive amounts of manpower to produce, as with all Japanese aircraft.

I'd certainly love to see the manhour totals and/or analysis for the manhour and material cost to make different fighters.

Keep in mind that a P-51 was like 2,000 man hours and a Spitfire was around 13,000 man hours.

See here for manhours to make P-51s; in October of 1941, it was 12000. Yes, NAA was just starting to make them.
Granted, Spitfire cost in manhours was pretty high. In 1940, 15200 manhours to make one.
Looks like Zero was at 10000 mh mid-war.

Also, to bolster your point, the Ki-61 had to have been one of the most expensive Japanese aircraft of the war given its weight, its high aspect wing, the absurdedly robust diving speed, and other advanced features and yet the Japanese built around 3,000 of them. Perhaps the Army's military planners were more likely to adopt expensive aircraft given that they didn't have to launch aircraft from carriers?

Ki-61 was IMO nothing special in that regard, rather a simple aircraft. Talk Japanese P-40 or P-51, if lighter?
Ki-45 is when the Japanese went expensive.

Though, I do have some questions about the Ki-61. Like, why? The Ki-44 was available earlier and offered similar performance. It just didn't make sense to make the Ki-61. And on top of that, the Japanese had already added MW50 to a DB601A. The Ki-61 just seemed like too much effort for very little advantage over the Ki-44.

Ki-61 was a good idea at 1st, but execution of that idea was not. Vs. the Ki-44 it was much rangier and with lower wing loading, just like the IJA loved it. It took too much time for Kawasaski to have what is basically a 1100-1200 HP engine in series production, by what time Japanese in-service radials were at 1500-1800 HP (Allied engines were even better). The Ha 140 was a trainwreck, both in timing and capabilities.
Ki-61 with a radial would've been a far more useful fighter, but that happened way too late.

I'm not sure that Japanese have added water/alcoho injection to the DB 601A of their production, care to elaborate?

Kawasaki making only the radial engines makes far more sense in hindsight, ditto for Aichi.

 

[AerialTorpedoDude69]

Ki-61 was a good idea at 1st, but execution of that idea was not. Vs. the Ki-44 it was much rangier and with lower wing loading, just like the IJA loved it. It took too much time for Kawasaski to have what is basically a 1100-1200 HP engine in series production, by what time Japanese in-service radials were at 1500-1800 HP (Allied engines were even better). The Ha 140 was a trainwreck, both in timing and capabilities.
Ki-61 with a radial would've been a far more useful fighter, but that happened way too late.

I'm not sure that Japanese have added water/alcoho injection to the DB 601A of their production, care to elaborate?

Both Germany and Japan had been experimenting with adding MW50 to the DB-601A. I think in Germany they had added it to submodels of the DB-605. The Japanese modded a 601A in the 30s to incorporate MW50, predating the German use of MW50 in the 600 series by several years.

I can't help but feel that with better aerodynamic design of the wing and MW50, the Ki-61 could have been a much better fighter, with little more investment from the Japanese.
BTW, a Ki-63 in 1942 would have been a pretty outstanding aircraft. Probably superior to a Ki-61 with laminar wing and MW50 in cost and performance.

Ki-61 was IMO nothing special in that regard, rather a simple aircraft. Talk Japanese P-40 or P-51, if lighter?
Ki-45 is when the Japanese went expensive.

Is the only expensive thing about the Ki-45 that it had two (Sakae or Zuisei, which weren't exactly high-end) engines? I think perhaps the wing design is also more expensive as well but otherwise, it does not strike me as being all that advanced an aircraft. I wonder how it would have performed with two Kasei 23a engines.

Bombers are perhaps better examples of expensive designs as they all weigh more and cost more than the Nick. But that is their designed role. There's a reason why the Japanese didn't make heavy bombers: they cost too much.

 

[GrauGeist]

I can't help but feel that with better aerodynamic design of the wing and MW50, the Ki-61 could have been a much better fighter, with little more investment from the Japanese.

The KI-61 did become a much better fighter when they changed the engine.

 

[tomo pauk]

The Japanese modded a 601A in the 30s to incorporate MW50, predating the German use of MW50 in the 600 series by several years.

Interesting.
Do you have some good source about the Japanese modding the 601A with MW 50 in the 30s?

I can't help but feel that with better aerodynamic design of the wing and MW50, the Ki-61 could have been a much better fighter, with little more investment from the Japanese.
BTW, a Ki-63 in 1942 would have been a pretty outstanding aircraft. Probably superior to a Ki-61 with laminar wing and MW50 in cost and performance.

A fighter with 12m wingspan and Zuisei (even if it is the best version available) does not strike me as a performer. Perhaps comparable with mid-line Zeros and Oscars?
Wing on the Ki-61 was nothing special ( NACA 2R profile,16% t-t-c at root), so there a laminar wing or a 'classic' thin wing is certainly an improvement. MW 50 is certainly a boon, especially when the high-octane fuel is as good as impossible to get; MW 50 is of no help at high altitude unless the supercharger is also good for high altitudes (the Ha 40 and DB 601A have had a mediocre S/C past 1940).

Is the only expensive thing about the Ki-45 that it had two (Sakae or Zuisei, which weren't exactly high-end) engines? I think perhaps the wing design is also more expensive as well but otherwise, it does not strike me as being all that advanced an aircraft. I wonder how it would have performed with two Kasei 23a engines.

We can take a look at USAAF aircraft, yearly averages for complete aircraft (ready for service, with guns, radios). In 1943, USA were paying for P-40 $49449, and for a V-1710 $11268. For a P-51, $58824 and for a V-1650 (average price is for cheaper -1 and more expensive -3) $16919. Add a prop and cooling systems and the total powerplant percentage is easily around 30% of the whole aircraft, or perhaps 13-14K US$ on a P-40 and ~20K US$ on a P-51. Just the engine itself was perhaps single most expensive part of the aircraft?
V-1710 being cheaper than the R-2600, let alone the R-2800, if more expensive (and more capable) than the R-1830s the AAF was buying. In 1944, V-1710 (includes 1-stage and 2-stage versions; P-38 used 1-stage engine) went down to $10561, while the R-2600 went to above $15000.

A 2-engined aircraft will also have a bigger fuselage, bigger undercarriage, bigger and more elaborate fuel system, usually a cockpit for another crew member - all the things driving the price up.
The A-20 was a lowest priced USAAF attacker that I know the price of. In 1943 the average cost was $110324, with two R-2600 on average being $26902 (2 x 13451); again, add propellers and oil cooling system and the powerplant price is easy at $30000 on a $11000 aircraft.

tl;dr: number of engines was a big factor in the price paid for the end product; two smaller engines usually cost more than one big engine of similar layout, construction and technological level; from the Japanese (and German) point of view, fuel consumption was a big deal, again a twin-engined fighter is in disadvantage

Kasei 20 series (versions without the fancy reduction gear) were 500 lbs heavier than the Ha 102, and were using bigger propellers, so installing them on the Ki 45 would've been quite a task. An 1-engined fighter with Kasei in the nose seems to me as a more realistic proposal.

 

[GrauGeist]

Regarding the MW50, I understand that it was first used operationally on the DB605 around 1944 - not the 1930's.

 

[GregP]

The irony of the P-47 is that the role it is most notable for is ground attack in which the turbocharger was an unnecessary expense and in fact added weight. A Corsair optimized for a land-based role would have been less expensive and in view of the much, much lower take off distance would have required less airfield preparation and without the complexity of the turbocharger maintenance would have been simpler.

I think the P-47 was, by a large margin, the overall best high-altitude fighter of the war in terms of numbers and BEING there. It was MUCH more numerous than the very few high-altitude Fw 190s and Ta152s, and could maintain sea level power up above 25,000 feet, which is WHY the P-47's high-altitude performance was so good. Late version (P-47N) were very fast up high and were going to be major trouble for anything they encountered up there, including Me 262s since they weren't too good up high and had low service ceilings relative to the P-47. The fact that P-47s had great armament and were pretty good at ground attack was an added bonus to being one of the best of not THE best high-altitude fighter produced in decent numbers. Where they weren't quite so good was up in the 15,000 to 20,000 foot range.

 

[AerialTorpedoDude69]

Do you have some good source about the Japanese modding the 601A with MW 50 in the 30s?.

I'm pretty sure you know it better than I do. I think it was Japanese Secret Projects I, Francillion's book, the section on the Ki-78 Ken. The project began in the thirties at Tokyo University before being taken over by the military and scrapped in 1944 IIRC.

Kasei 20 series (versions without the fancy reduction gear) were 500 lbs heavier than the Ha 102, and were using bigger propellers, so installing them on the Ki 45 would've been quite a task. An 1-engined fighter with Kasei in the nose seems to me as a more realistic proposal.

The Ki-83, heavy fighter, used the 18-cylinder version of the Kasei. But it never went beyond prototype. They should have been building these kinds of fighters much earlier but only did so toward the end of the war. I think it used the Ha 214 Ru, which I think is the turbo version of the Ha-104, but I'm not sure. They look almost identical although there's a cooling fan on the Ha-214 Ru for some reason.

(EDIT) I forgot that the Ki-63 used the Zuisei and not the Kinsei. Thanks for the correction. Had it used the Kinsei, they would have had a Ki-100 in 1942.
(EDIT2) Getting back to what you mentioned about the Ki-61 having better range, Susumu Kajinami mentioned that the rear fuselage tank on the Ki-61 was removed in the field to prevent it from exploding, particularly when shot from behind. This mod reduced the Ki-61's range but provided a lot more safety (he claimed this mod saved his life). I don't know what the actual range was, but with that tank removed, it was likely similar in range to a BF-109, which had worse range than a Ki-44.

 

[tomo pauk]

I'm pretty sure you know it better than I do. I think it was Japanese Secret Projects I, Francillion's book, the section on the Ki-78 Ken. The project began in the thirties at Tokyo University before being taken over by the military and scrapped in 1944 IIRC.

Now I know about that, thank you for the tip
It was certainly shortsighted from the IJA not pushing for an earlier and wider proliferation of water-alcohol systems in the in-service engines once they were aware of the good results. Not just on the V12 engines, but also on radials, since the radials were in much greater supply and use; the 1st two Ha-40 seem to be delivered in March of 1942, and the whole 1942 saw only 61 Ha-40 produced (for comparison, just Kawasaki produced 1112 Ha-25 engines and 199 Ha-115 engines in 1942).

The Ki-83, heavy fighter, used the 18-cylinder version of the Kasei. But it never went beyond prototype. They should have been building these kinds of fighters much earlier but only did so toward the end of the war. I think it used the Ha 214 Ru, which I think is the turbo version of the Ha-104, but I'm not sure. They look almost identical although there's a cooling fan on the Ha-214 Ru for some reason.

Think that we can agree that Ki-83 was a whole new ball game when compared with Ki-45
Japanese/Mitsubishi can build any quantity of airframes they want, unless they also have the engine to power them, these airframes will be collecting the dust in front of factory - the Ha-43 was manufactured in meager numbers, and Japanese were not exactly shelling out the turbochargers like GE did across Pacific.
Nobody prevented Japanese from making, in good quantities, an 1-engined fighter around the Ha-42 - an 18 cylinder engine that was in a far greater supply.

(EDIT) I forgot that the Ki-63 used the Zuisei and not the Kinsei. Thanks for the correction. Had it used the Kinsei, they would have had a Ki-100 in 1942.

Bingo.

(EDIT2) Getting back to what you mentioned about the Ki-61 having better range, Susumu Kajinami mentioned that the rear fuselage tank on the Ki-61 was removed in the field to prevent it from exploding, particularly when shot from behind. This mod reduced the Ki-61's range but provided a lot more safety (he claimed this mod saved his life). I don't know what the actual range was, but with that tank removed, it was likely similar in range to a BF-109, which had worse range than a Ki-44.

Yanking out the rear tank was certainly a way to reduce a range of an aircraft
A good feedback with company might've probably seen the introduction of cooled exhaust gasses being routed to the tank (like on the La-5 for the wing tanks), CO2 purge as on the early F4Us, or perhaps installation of a smaller tank that is also better protected, or a combination?
I don't think that even with a fuselage tank removed the Ki-61 would've had a shorter range then the Ki-44, the later was outfitted with just 128 US gals + 2x35 US gal drop tanks, while the Ki-61 arried 2x50 US gal drop tanks (200 L types), and started with 199 US gals with the rear tank.
(just why the Ki-44 used 35 US gal drop tanks is a mystery to me that aircraft was too good to pass for the IJA, yet they somehow missed the possibilities there)

 

[AerialTorpedoDude69]

Think that we can agree that Ki-83 was a whole new ball game when compared with Ki-45
Japanese/Mitsubishi can build any quantity of airframes they want, unless they also have the engine to power them, these airframes will be collecting the dust in front of factory - the Ha-43 was manufactured in meager numbers, and Japanese were not exactly shelling out the turbochargers like GE did across Pacific.
Nobody prevented Japanese from making, in good quantities, an 1-engined fighter around the Ha-42 - an 18 cylinder engine that was in a far greater supply.

Yes, you are right! The Ki-83 also required a lot of wind tunnel testing because the newly formed Rikugun had to study the aerodynamics of high horsepower engines on a twin.

I do not understand why the Ha-214 or Ha-104 weren't used on a single engine aircraft. It may have been because the Japanese strategic planners subscribed to the belief that certain engines were more feasible for use on bombers rather than on fighters. And as a result, fighters like the Ki-83 hadn't had sufficient amounts of development in 1942, when the Ha-104/214 were available. NASM stated that production of the Ha-214 began in 1940 but my guess is that's an error or it refers to when development began. Or it refers to the Ha-104, which seems to have been the base model, but IDK.

But there is some evidence here that Japanese war planners were heavily influenced by fears of supply interruption by the Allies because they consistently show preference for smaller engines over larger ones. Low weight and cost doesn't consistently dominate their thinking but it has a strong influence on it.

61 arried 2x50 US gal drop tanks (200 L types), and started with 199 US gals with the rear tank.
(just why the Ki-44 used 35 US gal drop tanks is a mystery to me that aircraft was too good to pass for the IJA, yet they somehow missed the possibilities there)

That is a good observation and I do not know. The numerous design variants of the Ki-61 also complicates this picture. From what I can tell, the Ki-61-Ia (ko) would have had a 550 liter fuel capacity with the rear fuselage tank removed. Which would mean it had a 150 liter advantage over the 109, plus large drop tanks. So you are, again, right that it would have had a longer default range. But then on top of that, the Ki-61 had better streamlining compared to the 44.

Even with the rear fuel tank removed, it probably had several hundred miles longer range. So was it range that influenced Japanese war planners? I think it was likely both performance and range considerations.

Regarding, the Ki-44's tiny drop tanks, test pilots had complained about the Ki-44's high landing speed (and probably a high takeoff speed as well). So you can imagine that any added weight and increase in frontal drag would have had additional adverse effect on takeoff. Throughout the war, JAAF advanced airbases had very poor runways in New Guinea. My guess is that larger tanks would have adversely impacted take-off runs to the point where they couldn't function in New Guinea or on any forward airbase which might explain why only the Ki-61, Ki-45, and Ki-43 were used in that theater whereas the Ki-44 only flew from China and probably northern Japan which had better airfields. But I have no evidence on this.

Also, from what I've read, when the Ki-61 was trialed against the Ki-44, it was tested against the Ki-44-I with a 1,200 HP engine, not the Ki-44-II. There is a good chance that when the IJA made the strategic decision to not use the Ki-44 in New Guinea, it was based on the 1,200HP version of the Ki-44, which was pretty much outperformed by the Ki-61. And then when field conditions in New Guinea showed serious defects in the Ki-61, the Ki-44-II had already been committed to air groups that weren't concerned with long range missions. A Ki-44 with slightly more development effort, such as provision for larger drop tanks, MW50, thrust stacks, and better designed wings would have been a tough competitor in New Guinea. But low-turbulence airfoils are difficult to use on short runways such as those found in New Guinea and other roughly hewn landing strips.

I've got to imagine that part of the reason the J2M wasn't used on many forward IJN airbases outside of Guam might have had to do with its high landing speed and long takeoff run and the poor state of forward Japanese airbases. However, US test pilots had a different take on the J2M, so I might be wrong about this. Even so, as you say, cost, weight, and other infrastructure and supply factors may have taken a backseat to other concerns.

 

[EwenS]

The first J2Ms went to the 602nd Hikotai of the 381st Kokutai to provide air defence for the Balikpapan oilfields around the end of 1943. The first air raid on Balikpapan by Australia based B-24s had taken place in Aug 1943 (the Shady Lady raid Shady Lady (aircraft) - Wikipedia). By Feb 1944 they had 10 on strength but little hope of getting more.

 

[tomo pauk]

I do not understand why the Ha-214 or Ha-104 weren't used on a single engine aircraft. It may have been because the Japanese strategic planners subscribed to the belief that certain engines were more feasible for use on bombers rather than on fighters.

The Ha-104 was almost as good as the 2-stage versions of the R-2800 B series, without the added complexity, drag and required volume for intercoolers. It was also lighter, 2080 lb vs. 2480 lb. The R-2800 was at 52.5 in diameter, vs. 54 in for the Ha-104.
Ha-42 familiy was one of rare late-war Japanese engine designs still running okay with 87 oct fuel, this should've rated it very highly by the Japanese planers. Granted, Mitsubishi was not making the Ha 42 in really great quantities.

 

[Passenger_57]

Wow, I had to look up the Metroliner. Why haven't they been grounded; that is a lot of crashes. Very TU-104esque.

 

[Passenger_57]

One place the Japanese had a lead was aerial torpedoes. Of course, almost the entire world had better torpedoes than we did when WWII started.

The Japanese were able to design an aerial unit that could be dropped into Pearl Harbor without hitting the bottom of the harbor. At the time, U.S. torpedoes were not very good and were never able to be dropped in quite as shallow water.

Those very successful torpedos were also a real threat to the ship as they were filled with oxygen and required extra oxygen storage. The explosives in their warheads were also much more susceptible to being detonated by shock. At least one IJN cruiser was lost when it torpedo tubes were struck.

 

[AerialTorpedoDude69]

Those very successful torpedos were also a real threat to the ship as they were filled with oxygen and required extra oxygen storage. The explosives in their warheads were also much more susceptible to being detonated by shock. At least one IJN cruiser was lost when it torpedo tubes were struck.

This is a misconception. The Japanese used a world-class torpedo, of conventional design, as its standard aerial torpedo, during World War II. The oxygen-propelled torpedo (of which there were several variations) was a radically different technology than what was used in conventional designs of that era. And it was not loaded onboard carriers (at least as a munition for a torpedo bomber). There's a good reason for that: You would not want an oxygen-fueled torpedo anywhere near a combustion engine.

There was a plan to create an oxygen-propelled aerial torpedo, but these things were huge and only Japan's four-engine flying boats could carry them. Of course, these plans were scapped because you just couldn't risk putting such a volatile system near a combustion engine. And they were absolutely gigantic, which is why their range was off the charts.

 

[GrauGeist]

Yes, the Type 93 (Long Lance) torpedoes were indeed large: 6,000 pounds and 31.5 feet long.

Which is a bit large to be carried by an aircraft.

As an aside, the Type 93 was large enough, that with some modifications it became a series of manned (suicide) torpedo.

 

[cherry blossom]

The Ha-104 was almost as good as the 2-stage versions of the R-2800 B series, without the added complexity, drag and required volume for intercoolers. It was also lighter, 2080 lb vs. 2480 lb. The R-2800 was at 52.5 in diameter, vs. 54 in for the Ha-104.
Ha-42 familiy was one of rare late-war Japanese engine designs still running okay with 87 oct fuel, this should've rated it very highly by the Japanese planers. Granted, Mitsubishi was not making the Ha 42 in really great quantities.

I agree that the Ha 104/Ha 42-11 was a reliable engine that might have seen more use but the dry weight that I have is 1140 kg or 2513 lb. Mitsubishi seems to have achieved reliability by running a fairly heavy engine with a large swept volume at relatively low revs giving 1900ps at 2450 rpm for takeoff and 1810ps at 2200m at 2400 rpm or 1610ps at 6100m at 2400 rpm.

There was a redesigned version called the 18E by Mitsubishi and Ha 42-21 or Ha 214 by the Army (MK10 by the Navy), which was heavier at 1235 kg or 2723 lb. Only photographs of those survive (from the crashed Ki-93 prototype when the rear cowling panel came away) but Goodwin and Starkings argue that Mitsubishi used the ideas from the Ha-43/MK9 such as driving the valves from two cam-rings rather than from the front as in the Kasei and Ha 104. That is said to have given 2500ps at 2600 rpm for takeoff and 2300ps at 2000 m and 2500 rpm or 2000ps at 6500 m and 2500 rpm. However, the Wikipedia article on the Ki-93 Rikugun Ki-93 - Wikipedia states that only 1970 ps was actually available.

Both the Ha-43/MK9 and especially the Homare were lighter (980 kg or 2160 lb and only 830 kg or 1830 lb).

 

[tomo pauk]

I agree that the Ha 104/Ha 42-11 was a reliable engine that might have seen more use but the dry weight that I have is 1140 kg or 2513 lb. Mitsubishi seems to have achieved reliability by running a fairly heavy engine with a large swept volume at relatively low revs giving 1900ps at 2450 rpm for takeoff and 1810ps at 2200m at 2400 rpm or 1610ps at 6100m at 2400 rpm.

The 2080 lb is the figure from the big TAIC manual. The Ki-67-specific TAIC report notes the weight of the engines as 2190 lbs (994 kg; it also mentions the water injection jets FWIW). The Bunrin Do book about the Ki-67 says 946 kg (2086 lbs).