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The only change I would make is relative to the effects that high grade 100/130 fuel could have had if available at the beginning of the war.
Using the Sakae 12 as an example. There is no reason that the Japanese could not have had ~1100 BHP at about the same 13,000 ft altitude where it had 950 BHP in real life. As it was with 87/92 grade the Sakae was limited to +3/+4.8 lbs, which was basically pre-war MAP for US and UK radials.
Obviously this is not a war winner, but the A6M2 would have gained about 15 mph at ~15,000 ft.
Somewhat address in previous post.Interesting discussion regarding fuels and japanese engines. What kind of power would the Sakae-21 do on 100 octane, and potential speed increase for A6M3/5? And same question for all variants of Kasei, Kinsei, Ha-41/109 etc., pretty much all major japanese engines. I know it's a lot, but i'm very curious about this subject. Is it a percentage increase? And how about the methanol/water injected late-war japanese engines running on 100 octane fuel, like Homare, Kasei-20 or Kinsei-60 series etc.?
I have read that one of the reasons they resorted to water/methanol injection (which brought all kinds of complications) for instance in the design of the Homare as early as 1941 i believe was the very lack of 100 octane fuel.
You did, basically altitude and cooling.I know there are many engined experts here, but if the above would be true, how do we explain the Merlin-III going from 1030HP on 87 octane to a whooping 1310 HP with 100 octane, almost 30% increase (there might be time and altitude limitations though)? I don't recall reading about any major modifications made on the engine.
If we go by a similar radio the Sakae-12 would do something like 1200HP on 100 octane fuel! And applying a roughly similar ratio we get something like 1400 HP for the Sakae-21?! But maybe i miss something.
Hey Shortround6,
re "You are not going to get 1100hp at 13,000 from the Sakae 12 because the supercharger won't supply enough air. You could get 1100hp at lower altitude though this assumes the engine will take the power and will cool at the higher power levels.
You can change the supercharger (bigger) to make 1100hp at 13,000ft on the Sakae . . ."
Or you can change the SC impeller ratio (Merlin 45 at 9.089:1 vs Merlin III at 8.588:1) and/or the impeller Ø (Merlin 46 at Ø10.85" vs Merlin III/45 at Ø10.25") - or both if the fuel allows the charge temperature increase - which I am pretty sure it would. A combination of the above would allow the relatively minor increase in MAP and power I am talking about for the Sakae 12. I have no way of knowing if the Japanese SC designs were of comparable efficiency to the 'Hookerized' types used on the Merlin, but the SC on the Sakei 12 and 21 were more efficient than the standard engine mounted SC designs used by the US radials and the V-1710 at the start of the war.
Again, you are I believe mostly correct in that changes would have to be made. Again however, I have to add that if 100/130 grade fuel had been available at the start of the war there is no reason I can think of that we would not have seen improvements in the Japanese engines similar to what occurred with the US and UK engines - particularly incremental improvements in strength and cooling. But I have no way of predicting what the Japanese Air Ministry would have prioritized, or if there were enough industry resources available.
My thought is that the 1942 A6M2 and Ki-43 had basically 1940 performance and armament. It did not get a lot better as the war went on. Perhaps they closed the gap to one year?
Criteria are in squadron service aircraft, not prototypes or service test.
The early fighters had great range, they sacrificed things to get it (firepower and protection).
The Japanese did face several handicaps. One was fuel quality, but you can't just pour in Allied fuel and get allied power levels. You often need better materials (another short coming ) and better cooling, which also may require changes in tooling and/or basic structure.
Interesting discussion regarding fuels and japanese engines. What kind of power would the Sakae-21 do on 100 octane, and potential speed increase for A6M3/5? And same question for all variants of Kasei, Kinsei, Ha-41/109 etc., pretty much all major japanese engines. I know it's a lot, but i'm very curious about this subject. Is it a percentage increase? And how about the methanol/water injected late-war japanese engines running on 100 octane fuel, like Homare, Kasei-20 or Kinsei-60 series etc.?
See the TAIC for this data.Does anyone have the supercharger impeller ratios and impeller diameters for the Sakae 12 and 21?
Kind of/sort of? we are crossing over. Most radials used a considerable amount of fuel for internal cooling at high power. The higher octane fuel, as you say, does not provide any additional cooling over a lower octane fuel. P & W R-2800 cut back the fuel by at least 1 gallon per minute when the water injection kicked in even though the engine was making more power.Unlike ADI, high oct fuel does not provide internal cooling, even with engines running overly rich.
The 3 British engines had the most minimal amount of work possible to get them to run on higher octane fuel, again you just can't grab the can/drum of high octane fuel and dump it in the fuel tanks and take-off. In some cases it was more to allow a plane to refuel if only high octane was available.Mercury XV went for some 20% increase in output, 100 oct vs. 87 oct. Pegasus was more modest, Perseus even more modest.