Originally posted by SgtPappy
haha, well that's interesting stuff, CPW. Where did you manage to find that information?
I also read somewhere that the Ha-42-21's being produced in wartime were also, like the airframe, of relative poor quality. It was meant to produce extra power but most of the Homare engines were built in such a way that they had to be modified to run with the 100/130 grade octane the U.S. was using.
I could be wrong, I'll look up the source from where I found it.
I bought some books and learned some Japanese:D
Actually from a Japanese military magazine which publicated in 1950-60s,the most serious problem on ki-84 was landing gear and hadn't described about any engine failure. So, it may solved before war end.
Originally posted by Elfie
I'm not so sure how accurate that is. Car engines can produce more power w/ higher octane fuel so why couldn't a radial aircraft engine do so as well? Both are internal combustion engines.
I searched for this in Japanese , Chinese and English webs, and they told the same answer.
For instance from IL-2 sturmovik game web:
For the case of the Ki-84 engine , the fact that you use higher octane fuel on it doesn't change anything AFAIK , it's still the same rate of air/fuel mix injected in less than 1 second going in the carburator , same rate of compression ..... it really doesn't change anything because the engine is not designed to accept higher octane fuel , engines need a minimum octane indice , but using a higher octane than what the engine has been designed for is useless , trust me this is for sure
link:
http://forums.ubi.com/eve/forums/a/tpc/f/63110913/m/4881000825 ----------------------------
Besides,octane too high would cause some problems(from WWII aircraft net):
Problems associated with the use of 150 grade fuel. 150 grade fuel P-38
Spark plug leading was increased. The extent of this leading was such that plug change was required after approximately 15 hours flying. This conditions was aggravated considerably by low cruising powers used to and from target areas, while trying to get the maximum range possible. It was found, however, that regular periods of high power running for a minute of two in most cases smoothed out any rough running engines unless the cause was other than leading.
P-51
The same type of lead fouling as described in a and b above happened in the case of the P-51 except that is was probably more serious than in either of the other two types. Using 130 grade fuel with 4?cc. of lead, the average operational P-51 could last 5 missions (roughly 25 hours) before the fouling required plug change. With 150 grade fuel containing 6 cc. of lead, 10 to 12 hours, or normally 2 missions, was the average length of time between spark plug changes or cleaning. At various times in the six months of operation of P-51 aircraft on 150 grade fuel many other maintenance difficulties were attributed to the fuel, but final analysis proved that the only real effect of the fuel was the lead fouling. Some units maintained that they had some deteriorations of seals, but this was not borne our throughout the command, nor was there any concrete evidence that it existed in the units.
The excessive fouling of spark plugs usually exhibited itself in roughing up of engines after a couple of hours of low power cruising. Periodic bursts of high power in most cases smoothed the engine out. However, if the engine was allowed to go too long a period without being cleaned out, the accumulation of lead bromide globules successfully withstood any attempts to blow them out. In some instances, long periods of idling while waiting for take-off and a failure to use high power on take off resulted in loss of power during take-off run and in some cases caused complete cutting out with subsequent belly landing. The cases of cutting-out on take-off definitely attributed to excessive fouling were comparatively few, although numerous enough to list it as an effect of the extra lead.
As a result of several months operational use with the fuel, an SOP ?designed to reduce power failures on take-off, leading troubles in flight, and other things which were causing early returns and abortive aircraft ?was published. This is inclosure no. 1. Almost immediately after this section published this SOP practically all of the troubles then existing ceased, although it was necessary to change plugs after each two missions or thereabouts.
P-47
Spark plug fouling was the only maintenance difficulty encountered during the period in which 150 grade fuel was used. Spark plug life was reduced by about 50%, the same low power cruising as described above being the principle cause for the extra fouling. No deleterious effects on diaphragms, fuel hose or any other rubber of synthetic rubber materials were noted.
