My referrence to the 'past discussions' has no bearing on making the Ki-84 in AH 'better'.
You mentioned:
A Captured Ki84 was brought up to over 420 (430?) mph in the US on US fuel.
The use of 100 octane fuel in that captured Ki-84 may have been used to simulate water/methanol.
Higher octane fuel detonates at a higher temp / pressure and should allow for a higher boost. But high Octane fuel run in an engine with a low compression ratio would not burn as clean and you would end up with a dirty intake and not much of a performance boost. Engine wear would be a problem as well because of the higher temp. Its not clear that simply putting US 100 octane gas in the Ki-84 tank would mean greater performance.
If the Ki-84 is without water/methanol then MAP limits for 87 octane will indeed mean a much slower plane then one with 100 octane or one with 87 + water / methanol. It wouldn't make sense that the US would have tested the Ki-84 with higher MAP settings then were used by the Japanese with 87 + water.
My point being is that the Ki-84 didn't necessarily need 'US fuel' to be a 'top performer'. Fuel is only one issue.
Below is a quote I provided from another forum (J-Aircraft Forum) in a past Ki-84 discussion on this A & V forum:
My argument is to eventually show that the American test claim of 427mph @ 20,000ft was quite naturally to be expected of a FRANK powered by the Homare Model 21 (and-it W-A-S a Model 21...), if the (older) figure of 388mph was derived from a prototype powered by Homare Model 11, and that it could have hardly done otherwise if the later model engine, in fact, did fully-attain its intended "design-to" power-level, especially @ higher altitudes.
Had the Americans captured some very early FRANK (especially-if powered by the (first) Model 11 engine...and, obviously, without the exhaust augmentation...), its "fame" would be nonexistent as we know it today; its max speed would hardly differ from that already quote in Rene Francillon's book:
“During the flight trials, the Ki-84 reach a speed a speed of 388 mph..."(pg.231)
I assert that the obvious difference in the two max speeds - merely shows the steady but intensive Nakajima effort at improving the "total" power plant output, by whatever means - more then the use of American avgas. (Although, ultimately, it may have needed to depend on the very high-octane gasoline-only the Americans had-to reach its "design-to" power-level, especially @ higher altitudes. Perhaps fortunate too was a "good" (production sample) engine that happened to be found in the FRANK example falling into Yankee hands...)
Anyway, here's a profile of how the two Homare models markedly different in their respective power levels @ all altitudes (AIREVIEW's General View of Japanese Military Aircraft in the Pacific War, Vol.1, pg.320):
Ha-45/11 NK9-B (IJN-nomenclature)
HP (T.O.): 1,800 @ 400mmHg & 2,900rpm
HP (2,000m/6,562-ft): 1,650 @ 250mmHg & same-rpm
HP (5,700m/18,701-ft): 1,460 @ 250mmHg & same-rpm
Ha-45/21 NK9-H (IJN-nomenclature)
HP (T.O.): 2,000 @ 500mmHg & 3,000rpm
HP (1,800m/5,901-ft): 1,860 @ 350mmHg & same-rpm
HP (6,400m/20,997-ft): 1,620 @ 350mmHg & same-rpm
Notes:
1- The Ha-45/21's more-oft quoted T.O.HP is: 1,990, in most other literature and the less often quoted (fully) 2,000Hp was more reserved for the "finally-arrived & matured" Ha-45/22, as the very next step, i.e., that the Model 21 was "almost" the Model 22.
2- Manifold Pressures (given in "inches") following the "boost” pressures (I translated the Japanese practice of merely quoting only the "boost” pressures (i.e., “gauge" pressures / above Standard Atmosphere (980mb), instead of the "total" pressure - that the Americans call: “Manifold Pressure"-which already includes the basic: 29.92-within their figures, become-translated:
Ha-45/11: (1st-speed): 400mm= 45.7" (2nd speed): 250mm= 39.8"
Ha-45/21: (1st-speed): 500mm= 49.6" (2nd-speed): 350mm= 43.7"
From this(and other sources...I also assert that the (earliest ) Homare (-11) engine can best be "profiled" as an:"1800/1400"engine, at best(meaning:
1,800Hp@S.L./1,400Hp@20,000-ft. (This is just my way of "stereotyping" these engines, for sake of illustration...)
Yet, Nakajima's goal was really "the mature Homare," as a fully arrived: "2000/1700"engine (meaning:2,000Hp@S.L./1,700 Hp@20,000-ft), and this power goal was to be "attained" by the Model 22. (Further power-improvements were also forthcoming, also w/more sub-models w/different blower-schedules, but I think "everyone" would just finally be happy when the "genuine" (and reliable...)"2000 / 1700" Homare, finally arrived...
Now, I do understand that these are (likely) “design to” goals, specified by contract as figures to-be-attained for a given production assignment, and not what really resulted in delivered products, to the field.
But anyway - so, what would (ideally) happen? Just what were the "simple" consequences of bringing your horsepower, up, from: 1,400 to-say...1,700? Well, if you did-388mph (on just 1,400Hp...), than by the simple cubic-root/law, you must now go-414mph! (In fact-you couldn't help it...)
So the next step remains: How do you finally get to: 427mph?
Simply by increase your "horsepower" to: 1,866. That's only just another 166Hp-would give that extra: 13-mph... So, where’s another way to get that extra boosting - without putting your engine in the garage?
That's all for now,
Robert
P.S. Tomorrow, I want talk about :
1- Exhaust Augmentation w/"actual"(likely) figures of: “pounds-of-thrust" including its real effect on speed...
2- Why power must still "drops / increasing altitude, even @ constant manifold pressure & rpm / delivery, and perhaps why high octane may be more efficacious here @ these higher altitudes, more than the lower-altitudes... (Although I think the two "engine" experts...we all know about...can explicate this better than I can...)
3- Further (more advanced) Homare models @ their (internal) dynamic specs...
4- What "may have happened" to the hapless Homare Model 22 engine in the original Reppu an (unexplained?) first class disaster for Nakajima (I was a propulsion-engineer / junior officer @ Wright Patterson AFB - and I know a "performance event / catastrophe" when I hear of one...)
Remember, I don't necessarily have the answers, but I want to bring attention to certain things, in certain ways...
Anyway my point was that you seem interested in the Ki-84 and I thought you may have an interest in the past discussions. I figured it be easier to point you in that direction then re-posting the above here once again.
I read the current discussion completely and can only wonder given your last reply:
What are you on about?
