Japanese Piston Engines

Thanks, I liked the one I mentioned as a good quick refrence, kind of like this Junkers website The Hugo Junkers Homepage

Hi Shinpachi,

>We regard the site itself as an edited data base because it covers not only Japan but U.S.A, Germany, Britain, France and Italy widely as if a volume of a book.

Ah, I see - thanks a lot!

Have you ever seen Japanese WW2 aircraft or engine manuals that state the operating parameters of the powerplants?

Such manuals appear to be the best source for reliable data, but so far, I've only seen a translated Ki-44 manual once which mentioned boost pressures and engine speeds.

As there seems to be quite a bit of confusion regarding the operating parameters of the various A6M models, it would appear that the manuals would help us out of this difficult situation, so any hint you might have would be appreciated!

Regards,

Henning (HoHun)

I'm kind of interested in finding out more on the Japanese inline engines.

Not so much the Ha 40/140/240 (dirivatives of DB 601/605), but the lesser known V-12's (the Ha 2-2, Ha 4, Ha 9, Ha 21, and Ha 46), the Ha 9 being pretty much the only one to see significant use. (though the Ha 2-2 was, somewhat unsuccessfully, used on the Ki-1 bomber)

Particularly the origins of the designs. (what the're based on, coipis/license built, or dirvatives of other engines, or if they're indigenos designs)

Hi HoHun.

I will translate descriptions about Sakae 21 from A6M3 Operation Manual.
Please give me a few days.

I fully understand your enthusiasm.
Thank you for asking me.

***********

Hi kool kitty89.

I'm also much impressed with your good knowledge about the Japanese engines. Please keep in touch with me as any information will be coming up

Well before reading that site, all I really knew of (besides the DB based engines) was the Ha 9, I foun out about the Ki-1 after doing a quick search on the Ha 2-2.

Thanks for the info and any more to come.

There's an english portion of that website too, WarBirds Is the database not accessible there?

Hello kool kitty89.
There seem no secrets about Japanese web sites today.
You are checking them very well
I know the site but not checking so well.
Thanks for the info.

Hi HoHun.
Here is my translation about the Sakae 21.

**************
Aircraft Engine

Name: Sakae 21

Number: 1

HP:
Nominal:
1,080 @1st stage of supercharger(on the ground)
1,100 @2nd stage of supercharger(alt. 2,850meters)
980 @2nd stage of supercharger(alt. 6,000meters)
Lift-off:
1,130


RPM:
Nominal: 2,700
Lift-off: 2,750

Manifold air pressure(Mercurial column in milimeter):
Nominal: +200*
Lift-off: +300

Nominal altitude(meter):
2,850 @1st stage of supercharger
6,000 @2nd stage of supercharger

Reduction Gear Ratio:
7/12 (0.5833)

Fuel:
Specific gravity: 0.72
Type: Aviation type92 volatile oil



Data Source: "A6M3 operation manual" at Japan Center for Asian Historical Records [Reference Code] A03032271200


*Note: Description about Manifold air pressure is indistinct.
It can be read "Nominal (0.25kg per square centimeter) +200 more or less with normal max(---) common for nominal 1st stage and 2nd stage" by Shinpachi's eyes.

Wishing any help for you

Hi Shinpachi,

>Here is my translation about the Sakae 21.

Thanks a lot! That is great stuff, very useful in improving the accuracy of our knowledge of the A6M

>1,080 @1st stage of supercharger(on the ground)
>1,100 @2nd stage of supercharger(alt. 2,850meters) <- actually 1st stage?
>980 @2nd stage of supercharger(alt. 6,000meters)

This is highly interesting - I had thought that the US TAIC engine data was based on guesswork (being war-time intelligence information), but their data was in fact identical to the Japanese rating you quoted. Here is the TAIC information:

Sakae model 21, TAIC 1944 p. 852
Take-off 1115 hp/2750 rpm/41.7" SL
WEP 1115 hp/2750 rpm/41.7" SL
WEP 1180 hp/2750 rpm/41.7" 7500*
WEP 1040 hp/2750 rpm/41.7" 18000*
MIL 995 hp/2700 rpm/37.8" SL
MIL 1085 hp/2700 rpm/37.8" 9350 ft
MIL 965 hp/2700 rpm/37.8" 19700 ft

Analysis:

TAIC and Japanese MIL rpm: match
TAIC and Japanese MIL boost: match (37.8" Hg = +200 mm Hg)
TAIC and Japanese MIL full throttle height: match
TAIC WEP and Japanese take-off rpm: match
TAIC WEP and Japanese take-off boost: match (41.7" Hg = +299 mm Hg)

At the first sight, the quoted powers do not seem to match, but it's important to remember that the international HP was 735.5 W while the Imperial HP was 745.7W, so the power figures match, too.

There is one value that is an exception, though:

>1,080 @1st stage of supercharger(on the ground)

This appears like a value that might be achieved at increased boost ... for +200 mm, 2700 rpm it seems to be too high as it almost matches the 1100 HP at 2850 m of the MIL rating, but mechanically-supercharged piston engines lose power as altitude decreases below full throttle height.

>*Note: Description about Manifold air pressure is indistinct.
It can be read "Nominal (0.25kg per square centimeter) +200 more or less with normal max(---) common for nominal 1st stage and 2nd stage" by Shinpachi's eyes.

Hm, this sounds like an important comment, but I don't entirely understand it ... could you explain it again, please?

Regards,

Henning (HoHun)

Hi HoHun.

You are checking everything.
Much impressed.

1. >1,100 @2nd stage of supercharger(alt. 2,850meters) <- actually 1st stage?

Yes, it was my mistype. It had to be typed as you pointed out.

"1,100 @1st stage of supercharger(alt. 2,850meters) "


2. >*Note: Description about Manifold air pressure is indistinct.
It can be read "Nominal (0.25kg per square centimeter) +200 more or less with normal max(---) common for nominal 1st stage and 2nd stage" by Shinpachi's eyes.

When I read them very carefully, contents look very simple as follows.

"Manifold air pressure(Mercurial column milimeter)
Nominal 225* * normal max (1st stage)
+200 @ nominal 1st stage, 2nd stage
Lift-off +300 "

Here attached my work-table images for your references.

Wishing any help for you!

I've been looking around for info on the varoius japanese V-12's, but haven't gotten anything really conclusive.


As the Ha-9 seems to have had been the most used (Ki-10 and Ki-32) I've been most interested in it, but still with little to no solid information.


It seems to be a copy or a development of the BMW VI engine, but there are still a couple problems with this. A couple sourses claim that the Ha-9 is a copy of the "BMW IX" engine. Through some other refrences I found that the BMW VI is somtimes erroniously called the "BMW IX" (including that Japanese engine site previously listed on the site).

The other problem is that the stroke given on that Japanese site (the only data I could find) is given as 170 mm instead of the 190 mm of the BMW VI. (the stroke being 160 mm) However, the volume given is 45.8 L, which would be correct for an engine with a 190 mm stroke, with 170 mm it should be 41.0 L. (note that the Ha-4 V-12 is also given 160x170 mm, but is listed with 41.0 L volume)



To make matters more confusing the Junkers L88 V-12 has identical bore and stroke to the BMW VI and has similar dementions and weight. (though in physical apearance it's quite different, being a cast-block engine with 4 valves per cylinder equipped with a reduction gearbox and doesn't have the prominent V in the top of the engine cowling)


Junkers Engines - L88
I mention the L88 as it was aparently lisenced by Mitsubishi for use on the Ki 20 bomber, additionally Ha-9's were used in the test program for the Ki-20. (which may be the Ha-4, but the listed stroke and volume don't match, as mentioned prevously)



Additionally the Mitsubishi Ki-1 was engined with 2x Ha-2-2, which seems to be the only other used of a liquid cooled V-12 by the Japanese. (other than the copies of the DB-601) The Ha-2 is listed as having a bore and stroke of 150 and 170 mm which would seem to imply that it is an indigenous design. (and due to the timeframe of its usage, it would seem to predate the L88, at least predate the lisence agreement with Mitsubishi)
Also, oddly, several sites (encluding en.wikipedia) list the Ha-2 as a "liquid cooled radial engine."


This immage shws the engines faily clearly, but at this angle it's difficult to discern much else about the engine. (if there is a prominant cylinder bulge V like the Ha-9's cowling, and it's difficult to tell if reduction gearing is used)





It should also be noted that the Soviets lisence built the BMW VI as the M-17, which lead to the development of the indigenous cast block AM-34 with identical bore and stroke to the BMW VI as well. This lead to the development of the AM-35 (MiG-1/3), AM-38 (Il-2), AM-42 (Il-10), and several similar dirivatives that didn't enter production.

It seems Kawasaki took a particular interest in the prospects of a liquid cooled V-12. Producing the Ha-9 and and developing several aircraft powered by it. With the Ki-10 biplane fighter and the Ki-32 bomber reaching production.
There was also a few other designs, most promising IMO being the Ki-28 fighter, the only Japanese fighter of the time to rival performance of the best contemporary European designs. (Mitsubishi's Ki-33 was also quite competitive
though)

And of course they eventually put this experience into the Ki-60 and subsequent Ki-61.


Mitsubishi showed some intrest as well, with their Ha-2 (as well as the Ha-4 and later Ha-21) along with the K-1 and Ki-20 bombers. Also the A5M3a with Hispano-Suiza 12X engine. (It seems odd that they didn't try their own Ha-2, though there seem to have been reliability issues)

kool kitty89 said:

And of course they eventually put this experience into the Ki-60 and subsequent Ki-61.

Click to expand...

Not to mention Yokosuka in its D4Y dive bomber. Japanese aviation has been an interest of mine for almost 30 years. Unfortunately, Japanese aero engines have never really held my interest beyond very basic information and are not my forte. However, my understanding is that the KI-60/ 61 and D4Y used licensed derivatives of the Daimler Benz DB 601. I wonder what the chances are that the info on the German engines would be similar to their Japanese counterpart?

I knew of the lisencing of the DB 601, I was more interested in finding out more about the "indigenous" Japanese liquid cooled engines and their origins. Or if they (or some of them) were simply licensed copies as well. (of older Junkers of BMW V-12 engines)

All that I can tell you is that there were no "indigenous" Japanese liquid cooled inline engines to the best of my (limited) knowledge of the subject.
Radial engines were generally viewed by the Japanese as reliable for ocean expanses and the elements for which the aircraft was expected to endure.
Simple. Reliable. Easy to maintain. Easy to repair. This was the focus.
The Japanese simply lacked the technological and logistical know how to operate complicated liquid cooled inline engines efficiently and reliably. They dabbled. This is why all inline engines from circa 1930 on were some version of a licensed built Daimler Benz knock off. It is also why- without exception- every Japanese inline engined aircraft was plagued with problem after problem (it is also a part of the reason why the KI-100 and D4Y3 was born). Not that their aircraft were necessarily inferior, mind you. But their technicians were too few, and inline engines were sort of a novelty for them that eventual war conditions would not allow them to develop the way that other nations had.
America had its Allison prior to the war.
Germany had its DB-600 series.
Britain had its Merlin.
But Japan had the nimblest fighter that the world had ever seen at that time- a radial engined fighter that became a legend.

As for the Japanese ever using Junkers derivatives, I have never heard of that. It certainly is possible, and some early aircraft certainly have that Junkers Jumo shape. Please share any knowledge of this that you may run across.

Well as I mentioned there were the Ki-10, which was the many army fighter prior to the introduction of the Ki-27. And the Ki-32 bomber Both bulit by Kawasaki using Kawasaki's Ha-9 water-cooled V-12.

I know they had many problems with production and reliabillity of the DB-601 copies, but I haven't seen much mentioned about problems on these 2 aircraft. (save a mention of cooling difficulties)

These engines would apear to be far simpler than the DB 601, though I haven't seen any pictures of the bare engine, it at least lacked reduction gearing and was very large (~2800 cubic inches in volume).

It may have been a copy or dirivative of the BMW VI engine (some refrences to the Ha 9 mention it being a licened version of the "BMW IX," for some reason several Japanese refrences call the BMW VI the BMW XI). But there are also the Junkers L55 and cast-block L88 of identical bore and stroke. (not to mention the Russian Mikulin engines dirrived form the BMW design, though developed considerably further)


If it's the BMW VI, the design if a development of the WWI vintage 6-cylinder inline BMW IV. Basicly 2 BMW IV's joined to form a 60 degree V-12. A simple design using individual steel cylinders with 2 valves per cylinder. No supercharger was used and no reduction gering was fitted. (running below 1,800 rpm, though the Ha-9 ran considerably higher at ~2,200 rpm and produced significantly more power)

I laud your knowledge of Japanese aero engines, kool kitty89. The KI-10 "Perry" predates my interest in Japanese WWII aviation (as do the others that you have mentioned). Research can be such a huge pain, sometimes. I often have to try several different tacks to get what often turns out to be a simple answer to a simple question. Detailed information on Japanese equipment is severely lacking, compared to U.S. and German items it seems.
Perhaps researching the specific aircraft (the design team, etc.) might assist you. I found it interesting for example to learn that the KI-10 "was designed by Japanese aeronautical engineer Takeo Doi, who had succeeded Richart Vogt as chief designer for Kawasaki".

Richard Vogt (aircraft designer - Wikipedia, the free encyclopedia)

Richart Vogt? A European chief designer for a Japanese aeronautical company (from 1923 to 1933)? He had nothing directly to do with the KI-10 (or probably any of the others), but I bet that his legacy did.
He returned to Germany in 1933 and accepted an offer with Blohm Und Voss. So the engines used in the aircraft that you mentioned were most likely of European design, but built to Japanese standards.
Anyway, good luck with your research. I encourage anyone who has knowledge and/ or data on this subject to kindly share it with all of us.

My understanding of the Ha-40 / Ha-140 series engines was that they were not DIRECT copies of the Daimler Benz equivalents but were lightened and had additional Japanese adaptions. I was told that the Japanese had issues with very large castings that would be required for Inline engines. Radials don't have very long castings.

Back to an earlier subject, the Nakajima Sakae series engines:
I have gotten from different sources that the compression for these engines is somewhere between 7.0 to 1 and 7.2 to 1. Which is correct? The US source for the 7.0 to 1 appears to be crude measurements of the engine of a captured A6M3 Model 32.

Is there similar data for the Sakae 12?

Thanks.
- Ivan.

If the castings were a major cause of the problems, that would explain why there weren't such issues with the Ha-9.

Though like I said I don't have many specifics on the engine, though the BMW VI would be the most logical to be the basis for it, given its prominant use in Germany in the 1930's.

In some sources is mentioned that prototype Ki-1 flew with Rolls-Royce Buzzard engines.

Wasn't Mitsubishi Ha-2 a development of Buzzard?