Japanese Engine Research, Page 2


Tentative Identification — Army Type 98 450Hp Radial (Army Ha13 "Ko")

This engine is a member of the Amakaze 20 series family of engines. Its Navy specification counterpart would be Amakaze 23. While this engine has a heavy preservative coating on it that doesn't make for "pretty" photographs, its similarities to A19670090000 are apparent. The differences stand out too. The adapted constant speed prop system in not there; it has a simple two speed prop control. Pushrod tube design is a little different and the ignition harness is installed on the aft side of the cylinders.

NOTE: The "Tentative" identification status is only a reflection of its lack of a data plate. The engine accessories and construction details match the information listed in the Army manual for the Army Type 98 450hp engine. The missing data plate may have been "souvenired" prior to its arrival at NASM or may have been removed by Technical Intelligence unit personnel at the time of its capture. Tech Intel units gathered data plates throughout the war with the goal of identifying possible targets for production sites. Large serial number ranges reflected large factory outputs, and therefore large potential targets for U.S. bombers. I have seen copies of leaflets distributed to Allied troops that warn against "souveniring" in the combat zone, so this information could be collected by Tech Intel teams. Personally, I am still holding out hope that somewhere, in some government warehouse, that there is a large crate full of Japanese data plates! It could answer a lot of my questions!


Ha31-21 (Zuisei 21, Army Type 1 -- 1,050 hp Radial, Army Ha 102)

Right engine for NASM's Ki 45 Kai Hei "Toryu" (Dragon Killer)
Allied code name: "Nick"
Displacement is 28.0 l, two speed supercharger, 1.118 m diameter and 565 kg dry weight.
Sources say 7,852 Zuisei 21s were built for both the Army and Navy. (This should be considered an approximate number and has yet to be confirmed)


I wish they were all this easy. Identified by stampings in the nose case and confirmed by the carburetor data plate. It is confirmed as the right engine because it is fitted with a hydraulic pump; the left engine is fitted with a vacuum pump. (Nick installation)
Note the use of ejector stacks instead of an exhaust collector ring as in earlier Zuisei 21s.


Ha32-21 Mitsubishi Kasei Model 21 (MK4P)

Displacement: 42.1 Liters
Bore: 150mm, Stroke: 170mm
1,850Hp (Metric) @ Takeoff
1,680Hp (Metric) @ 2,100m Low blower rated with Anti-Detonation (water) Injection (ADI)
1,570Hp (Metric) @ 5,500m Rated high blower with ADI
Double planetary spur reduction gear, Ratio: 0.538
Dry weight: 780kg
Diameter: 1.340m

Available in about 18 different models, the Kasei was one of Japan's most produced engines. Approximately 9,323 Kasei Model 20 engines were built during the war. The Model 21 powered the Mitsubishi G4M2-22 Navy Type 1 Attack Bomber (Allied code name: "Betty 22") and others.


Ha32-22 Mitsubishi Kasei Model 22 (MK4Q)

Displacement: 42.1 Liters
Bore: 150mm, Stroke: 170mm
1,850Hp (Metric) @ Takeoff
1,680Hp (Metric) @ 2,100m Low blower rated with Anti-Detonation (water) Injection (ADI)
1,540Hp (Metric) @ 5,500m Rated high blower with ADI
Planetary bevel reduction gear, Ratio: 0.500
Dry weight: 750kg
Diameter: 1.340m

The nose case tells the story. This is a Kasei 21 redesigned to accept a larger diameter four-blade propeller. Specifically for the Kawanishi H8K2-12 Navy Type 2 Flying Boat (Allied code name "Emily12").


The Kanji on the nose case reads "Kasei 22 Model".
The numbered photo points out a few details in the ADI system and the ignition system.
#1) Points out the ADI discharge control valve. The same on all ADI equipped Kasei's. Directly connected to the manifold pressure regulator, it controls the flow of water/methanol mixture at boost numbers over +160 mm/hg.
#2) Manual control of ignition advance. This is a feature of all Kasei models and allowed the pilot an adjustment of about 8-10 degrees in the ignition timing depending on the magnetos installed. (32 degrees BTDC maximum advance on all engines).
#3) Line connection for the ADI manifold. This is a horseshoe shaped manifold with the open end of the shoe at the bottom. Inlet on the top as you see it and drains on the bottom. If the engine has this fitting it is equipped with ADI.

Army Type 1 1,050 hp Radial (Army Ha102, Mitsubishi Zuisei 21)

Information is the same as the Nick engine, but I can't say for sure what this unit was installed in. The presence of a data plate and the early 1944 production date suggests this engine may have been equipped with an exhaust ring. Other applications for the Zuisei 21 were early versions of the Army Ki-46 (code name "Dinah") and the Mitsubishi MC-20v (code name "Topsy")

Note the identification is confirmed on the carb data plate and the minor change in float level compared to the Nick engine.


The accessory case photo shows a good view of carburetor detail. On top is a manual mixture control (via float chamber vent control) and an automatic manifold pressure regulator. The blank entry on the carb data plate under "economizer" is due to the fact that the manifold pressure regulator performs this function.