Either of these engines will me making 1250 HP at 5.5 km or more. A far cry vs. the Sakae making 950 HP there, and Zero was reasonably combat effective with that engine in the nose in that time.
We'd been giving up mostly the low price, since the next-gen fighter will not be as cheap as the Zero.
Range/endurance is a thing of how much of the fuel is carried vs. the engine power (consumption), a thing that bigger tanks were solving from the Wright Flyer days. Point of the more powerful engine in the nose is that one needs to sacrifices less, not more, so protection should be mandatory.
Well, the Homare was
supposed to make a lot more power, so lets look at the power at altitude and the weight of the engines.
Sakae 12...................950hp.....................4200 meters.......................530kg
Sakae 21...................980hp.....................6000 meters.......................590kg
Kinsei 54.................1100hp....................6200 metes.........................-------
Kinsei 62.................1250hp....................5800 meters.......................--------
Ha-109.....................1220hp...................5200 meters.......................720kg
Kasei13....................1300hp....................6000 meters.......................------
Kasei 15...................1280hp....................6000 meters.......................------
Kasei 21...................1410hp.....................4200 meters......................------
Homare 11..............1460hp...................5700 meters......................830kg
Homare 21..............1620hp...................6200 meters......................830kg
R-1830 -86..............1040hp...................5600 meters......................710kg
My copy of "Japanese Aero-Engine" is missing 4 pages, corrections/additions welcome.
What Japanese engines were coming available when in 1942/early 1943 is very important. The Kasie engine used in the J2M2 took quite a while to sort out. Perhaps the Bomber version of the engine could have been used or one of the bomber engines that were used in the G4M series of the time, which is why I threw in the Kasie 15.
The Improvement from the A6M2 to the A6M3 was significant. However it is sort of overshadowed because the A6M3 didn't have the range needed to fly the Rabaul to Guadalcanal missions (at least not at first) and with the destruction of the Japanese carriers there were only two carrier battles after Midway in 1942 in which the forces involved were much smaller than at Midway. After the Battle of Santa Cruz there was an 18 month gap in carrier battles.
There was a lot of Island to Island combat and there was US carrier vs Japanese Island combat going on.
The Zero spiraled down as the Sakae 31 engine never gave the increased power promised and any/all improvements hurt the performance of the A6M5 aircraft.
The Kinsei 54 might have held up the Performance of the A6M with the improvements but not increased it by much.
There is a fine line where a 1220-1300hp engine is going to give the needed performance in late 1942 and 1943 (F6Fs don't begin to show up until Aug 1943?) to allow the Japanese to retain superiority over the US Army fighters in the Island to Island fighting.