Ki-43 Hayabusa & Engine Performance - Grok Edition

[Laurelix]

I basically went and got the official numbers for Ki-43-I and Ki-43-II and Ki-43-III Ko and the engine power curves and got Grok to calculate it all, so now we have better idea of the power at other altitudes the sources don't state but are based off the real test flight speeds.

And now for the Grok Stuff

Now for the Max Speed and Climb Rates
Note: Ki-43-I and Ki-43-II only have Military power, WEP is purely take off power - 1 min rating. Only Ki-43-III Ko has water-methanol boost - 10 mins
(This is why the source gives Military power max speed for Ki-43-I and Ki-43-II but then gives WEP speed for Ki-43-III Ko)

Grok Estimated Sustained Turn Times (not max best time, not 1 circle instantaneous turn) - No Flaps Used
Ki-43-I ~13.5 seconds (Military Power) / WEP strictly 1 min for take off
Ki-43-II: ~16.0 seconds (Military Power) / WEP strictly 1 min for take off
Ki-43-III: ~16.5 seconds (Military Power) / ~16.0 Seconds (WEP)
[Note: This is at SL-1000m altitude]

Other Sources used for the Grok to put the engine power curves and performance data together:

Credit: ブログ内性能記事リンクまとめ : WW2航空機の性能:WarbirdPerformanceBlog

Ki-43 Nose variations

Honourable Mention -- Ki-43-III Otsu

 

[AerialTorpedoDude69]

I agree with you that synthetic numbers can be useful if we also have data from primary historical records.

I've wondered about the Ki-43-IIIKo's top speed of 558KPH? It seems a little slow for a refined version of the Ki-43 with MW50 injection. I originally assumed that this speed was the top military speed, without water injection, because IIRC it's mentioned that it was faster than the Zero in one of the Japanese publications, but 558 is slower than the A6M5.

 

[Laurelix]

I agree with you that synthetic numbers can be useful if we also have data from primary historical records.

I've wondered about the Ki-43-IIIKo's top speed of 558KPH? It seems a little slow for a refined version of the Ki-43 with MW50 injection. I originally assumed that this speed was the top military speed, without water injection, because IIRC it's mentioned that it was faster than the Zero in one of the Japanese publications, but 558 is slower than the A6M5.

Ki-43-III Ko's Ha-115-II engine at military power offers more or less identical power as Ki-43-II at 6000m at military power. So you can imagine why 555-560km/h at 6000m would be unrealistic to be at military power, even the most refined Ki-43-II does 535-540 at 6000m at military power at best.

A6M5 has 565km/h at 6000m at military power, the Ki-43-III Ko needs to use 10 min boost to achieve 558km/h.
That being said, the A6M5 has no WEP. A6M6 on the other hand is A6M5 with Sakae 32 engine with WM Boost

 

[AerialTorpedoDude69]

Ki-43-III Ko's Ha-115-II engine at military power offers more or less identical power as Ki-43-II at 6000m at military power. So you can imagine why 555-560km/h at 6000m would be unrealistic to be at military power, even the most refined Ki-43-II does 535-540 at 6000m at military power at best.

The source that you have mentions that the purpose of MW50 injection on the Sakae 31 was not to improve performance but I think for fuel "reliability" so to reduce knock and fuel fouling of the engine. So everything you say makes sense.

 

[taly01]

My thoughts on the Ki43-III MW injection, is that it boosted speeds mostly at below critical altitudes (as it allowed higher pressures then).........however the peak speeds were not that much higher as they were at the supercharger critical altitude (where pressure could no longer be reached) but combined with thin air it did reach peak speeds then etc. So i don't really agree with the guess-timation the grokAI used to make those tables, but I agree they are a rough baseline.

P.S. i have built flight models for the Ki43 series in il2-1946 and they basically match the final data you show there. I will find my .xls of the results tomorrow.

 

[Laurelix]

My thoughts on the Ki43-III MW injection, is that it boosted speeds mostly at below critical altitudes (as it allowed higher pressures then).........however the peak speeds were not that much higher as they were at the supercharger critical altitude (where pressure could no longer be reached) but combined with thin air it did reach peak speeds then etc. So i don't really agree with the guess-timation the grokAI used to make those tables, but I agree they are a rough baseline.

P.S. i have built flight models for the Ki43 series in il2-1946 and they basically match the final data you show there. I will find my .xls of the results tomorrow.

the 550-560km/h at 6100m is the official speed by japanese sources.

 

[taly01]

Here is my il2-1946 ki43 tuned flight models.

NB: I did air starts at 100m for climbs so add some +15 seconds to them.

When I get back to il2-1946 I may do 1000m interval speed tests esp. for ki43-III vs Ki43-IIKai, it should have larger speed differentials the more below critical altitudes are, that is the FLAW in GrokAI, it just gave a flat 20kph over all heights.

 

[Laurelix]

Here is my il2-1946 ki43 tuned flight models.

NB: I did air starts at 100m for climbs so add some +15 seconds to them.

View attachment 894763

When I get back to il2-1946 I may do 1000m interval speed tests esp. for ki43-III vs Ki43-IIKai, it should have larger speed differentials the more below critical altitudes are, that is the FLAW in GrokAI, it just gave a flat 20kph over all heights.

Ki-43-IIa is listed as only 515km/h at 6000m, 3:30 to 3000m rate of climb, 5:49 to 5000m

 

[mad_max]

From what I've read through many years about MW by use Japan was the fuel octane was incredibly low in the later years and it was used to save the engines from coming apart from cylinder detonation pressures.

They had to work with 87 octane, or even sometimes mixed with a volatile oil extracted from pine tree roots that lowered the fuel to 85 octane. It was so contaminated with impurities that American Jeeps that used this fuel during occupation suffered engine failures.

 

[taly01]

They had to work with 87 octane, or even sometimes mixed with a volatile oil extracted from pine tree roots that lowered the fuel to 85 octane. It was so contaminated with impurities that American Jeeps that used this fuel during occupation suffered engine failures.

Very amusing

That Ki43 Oxygen Injection Flight Test (....weird translation somehow I'm sure) I believe is for a very early Ki43-II. There is also talk that the early Ha115 was derated a bit.

My il2:1946 Ki43-IIa data is maybe more of a hybrid IIa-IIb with streamlined cowl but side exhausts. As I made it for 43-44 scenarios, Captain Nango said in his diary then that it made 550kph! The good thing with il2:1946 is that it is with real aero equations (even if simplified). I am sure AI could come up with good data, if it had actual aero equations etc otherwise its probably just doing some averaging.

The consensus for the Japanese terms for Ki43-II are now initial, early, middle, late, final. I should really call my Ki43-IIa a Ki43-II middle,

Roughly defined as-
Initial- long wings and cowling horseshoe oil cooler
early-shorter wings and enlarged undernose oil cooler
mid- streamlined nose cowling and backseat armour
Late-backward facing exhausts and wing landing light
Final/Kai-multiple Ejector exhaust stacks and underwing bomb racks outside of landing gear

 

[SaparotRob]

Very amusing

That Ki43 Oxygen Injection Flight Test (....weird translation somehow I'm sure) I believe is for a very early Ki43-II. There is also talk that the early Ha115 was derated a bit.

My il2:1946 Ki43-IIa data is maybe more of a hybrid IIa-IIb with streamlined cowl but side exhausts. As I made it for 43-44 scenarios, Captain Nango said in his diary then that it made 550kph! The good thing with il2:1946 is that it is with real aero equations (even if simplified). I am sure AI could come up with good data, if it had actual aero equations etc otherwise its probably just doing some averaging.

The consensus for the Japanese terms for Ki43-II are now initial, early, middle, late, final. I should really call my Ki43-IIa a Ki43-II middle,

Roughly defined as-
Initial- long wings and cowling horseshoe oil cooler
early-shorter wings and enlarged undernose oil cooler
mid- streamlined nose cowling and backseat armour
Late-backward facing exhausts and wing landing light
Final/Kai-multiple Ejector exhaust stacks and underwing bomb racks outside of landing gear

Zero it is.

 

[AerialTorpedoDude69]

From what I've read through many years about MW by use Japan was the fuel octane was incredibly low in the later years and it was used to save the engines from coming apart from cylinder detonation pressures.

They had to work with 87 octane, or even sometimes mixed with a volatile oil extracted from pine tree roots that lowered the fuel to 85 octane. It was so contaminated with impurities that American Jeeps that used this fuel during occupation suffered engine failures.

The US military declassified the official report on Japanese fuels (this document is available online). I believe that after the US cut Japan off from high quality oil as well as hard-to-make fuel doping chemicals, the IJN/A were forced to use highly aromatic fuels from numerous other locations. In addition to this, they also were forced to use synthetically created, pine root oil as a fuel additive. It was probably used as an additive because its 95-octane rating functioned as an octane booster (this is not explicitly states in the report) when mixed with lower octane fuels.