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Jun 5, 2013

Chi Ri II - Japanese tier 6/7 medium

Author: Soukoudragon (US forums)

A practical merging of the Chi Ri and Chi To

With the name Chi Ri II, the patterned way of thinking would figure that this Chi Ri II would be a better tank than the Chi Ri.

Well... yes and no.

Let’s look at Germany. The Tiger 2, the Jagdtiger, the Maus…bigger is better was the trend. But bigger meaning better is highly debatable. What if Germany made more of less complicated and lighter fighting machines? Well, the E-series was apparently going to help with that… a little.

With that concept in mind, the Chi Ri II was designed to be more practical than the Chi Ri. The designers were considering the final desperate battle for the homeland of Japan. They imagined destroyed bridges and railroads, the need to transport over water with landing craft, limited resources, and so on. A simplified Chi Ri sounds like a good idea, thus a better tank…for this kind of dire situation. However the war ended before development could begin.

The other point is that the Chi Ri II took many characteristics from both the Chi Ri and the Chi To while removing some characteristics from the Chi Ri. It could be said that it is as much a Chi Ri II as it is a Chi To II.

Characteristics to be borrowed from the Chi Ri (likely a none exhaustive list)

   Electrically moved Turret rotation.
   The wide 600mm treads.

Characteristics removed from the Chi Ri

   Secondary 37mm cannon.
   Large H9II gasoline engine. This enabled reducing the size of the hull.

Characteristics borrowed from the Chi To (production model).

   Similar 7 road wheel style coil spring suspension
   Upper front hull armor sloped (Chi To production model still has a better slope)
   400 HP diesel engine supercharged to 500 HP for the Chi Ri II.
   Very similar turret.

Main armament was the Type 5 75mm cannon.
Shell Weight: 6.615 kg
Muzzle Velocity: 821 m/s
Kinetic Energy: 2229 kj
Historical Pen: 75 mm (1,000 meters) goal (met), 80 mm (1,000 meters) expected

There is really nothing innovating about this tank. Bringing the good points of both the Chi Ri and the Chi To together created a stable and sound tank design.

In terms of WoT, the answer to the question “better” is where the “no” comes in. The simplification and practicality delivers a tank that is somewhat less, or perhaps, equally potent to the Chi Ri. Therefore the Chi Ri II could be either a tier 6 or tier 7 tank and not a tier 8 tank.


Front Upper Hull: 75mm
Front Lower Hull: 50mm
Side Hull: 35mm
Top Hull: 20mm
Rear Hull: 35mm
Bottom Hull: 16mm

Front Turret: 75mm
Side Turret: --
Top Turret: --
Rear Turret: --

Estimated values for optional cannons

Tier 6 Type 5 75mm model II (no auto loader)
AP Damage: 135
AP Penetration: 137
Rate of Fire: 14.5 r/m
Accuracy: .36

Tier 6 Type 5 75mm model I (single tray auto loader)
AP Damage: 135
AP Penetration: 137
Rate of Fire: 19 r/m
Accuracy: .36

Tier 7 Type 5 88mm cannon
AP Damage: 220
AP Penetration: 144
Rate of Fire: 10 r/m
Accuracy: .38

The 88mm cannon may be a bit of a squeeze but looks feasible, especially for WoT purposes.

Weight is about 35 tons. The 500 HP supercharged Mitsubishi AL Type 4 V12 diesel engine gives a 14.2 hp/ton rating. This is undoubtedly the weak spot in the Chi Ri II as far as game implementation is concerned.


It is quite a bit smaller than the Chi Ri and thus a common size medium tank.

Length: 6,492
Width: 3.05
Height: 2.792


The weak spot is the hp/ton rating. With 14.2hp/ton, it just cannot compete with the other tier 7 medium tanks in mobility. All the other attributes such as firepower, armor, and soft stats are workable in tier 7 if mobility was good enough. The weak engine bumps it down to tier 6 quality. There are no other engine options available for the Chi Ri II. The large H9II engine would be too large to fit in the Chi Ri II, thus shutting access to the H9II’s rich de-tuned upgradability.


Maru [丸] 2011 October magazine edition. 平成23年10月一日発行 
WoT Discussion forum: Japanese Tank Tree & Guns Discussion: posts by Daigensui


  1. A supercharged diesel engine? Really?

    Sounds weird to me. Probably this is supposed to be turbocharged instead?

    1. Diesels have been roots-type supercharged before.

      SO a Turbo-charged engine would give more power...

      HOWEVER. In my own research into aircraft engines supercharged can mean turbo-charged. And it can get insanely confusing as to which type of supercharger they are talking about even with the primary source. Only a careful reading of the source can tell us, in context, which supercharger it is.

      Turbo is usually mentioned as a Turbo-charger. And what we think of as a normal supercharger is a Roots type supercharger.

      However a 3ed type exists. a Turbo-supercharger. Which uses both types to allow an engine with a turbo charger to be efficient due to the bend in the turbo piping. As best I recall, the air passes through the turbo through the cooler and into a supercharger then engine then back to the turbo.

      More Reading:

      Yah I know its a bit "over-the-top" But it should answer most of your questions.

      The reason I even have any of this stuff on hand is because I have been researching about the XF-12 "RC-12" "Rainbow" by Republic Aviation. A sexy looking plan even by today's standards. I also have flight manuals discussing, in 1942 and 1954, supercharging and problems and solutions for aircraft engines. Its a hobby. One of many.


    2. No Problem. I am into turn of the century tech in terms of cars. The Vanderbilt Cup got me hooked into research and cars and then it went off from there.

      So now I cover
      Guns 1840 to 1900.
      Cars 1900-1971.
      WW1 and WW2 Tech.
      WW2 Submarines being my largest hobby currently
      XF-12 and its tech.

      I also have a growing collection of books on engineering (1903-1950s) but my digital collection is much bigger... passed 30gigs in digital books. Just for engineering and design. Another 7 gigs on novels. =)

    3. Leopard 1 has a supercharged diesel engine too. Thats why it sounds so awesome (not ingame).

    4. The Leo I doesn't have a native diesel engine though. It did have at the beginning but multifuel was planned and eventually equipped later to all of them. But I don't want to be pedantic. Basically you are right! Twin supercharged even.

      And thanks to Nemo for the hints.
      It is not so much that I had any questions about it. I just wanted to be sure that this isn't a mistake. I have never heard of supercharged diesel engines before and I could think of some good reasons for not supercharging a diesel engine.

      But all right, it is correct. A supercharged diesel engine.

    5. It works. But a turbo is much more efficient at giving the engine power. A roots-supercharger uses engine power to add power. However it also add that power over the whole engine curve. But a turbo adds power at, usually calculated and designed, a specific rpm.

      And with a diesel you can have the Tubos create a lot of power at very low rpms. High speed, as in 5k rpm, diesels don't really exist until like the 60's 70's due to how a diesel works.

      What was the most Powerful Tank Diesel used by America during WW2?

      Also with tank engines in the Panther through Tiger II they were limited to 3k rpm. I have seen reports of over revs to 3200 which meant that the Germans started putting a governor on the engines to preserve engine life.

      A diesel has very low horsepower without any supercharging for its displacement and adding a supercharger only adds to the mechanical problems that could occur not to mention cost to build. A turbo also adds cost to maintenance on top of, like a roots type, the additional heat and stresses on engines (Maybach HL230) that already had almost every corner cut on it to ease production stress and still give power.

      Plus one source of fuel kept things simple. Which is why the USA used gasoline for the most part.

      The M10 tank destroyer did use the:
      General Motors 6046 Twin Diesel 6-71 375 hp (276 kW).
      Power/weight, 12.5 hp/ton.
      Weight 29.6 metric tons (65,000 lb)

      Considering that even the Panther:
      Maybach HL230 P30 700 PS (690 hp, 515 kW)
      Power/weight 15.39 PS/tonne (13.77 hp/ton)
      Weight 44.8 tonnes (44.1 long tons; 49.4 short tons)

      And that you need a lot more engine to get an equal power from a diesel compared to a gasoline... Its no contest. Plus gasoline engine does have the advantage of higher rpms, which was needed on the German tanks due to the engines being directly connected to the turrets. Plus the added advantage of one engine design for over 7800 tanks is an ease on manufacturing. Diesel engines also need more metal in them due to the extra forces from compression ignition.

  2. >The 500 HP supercharged Mitsubishi AL Type 4 V12 diesel engine
    >A supercharged diesel engine? Really?

    December 1945 - US Naval Technical Mission to Japan - Japanese Navy Diesel Engines - INDEX No. S-42, p34

    "Limited production had been begun on V-12 Type 4 tank engine, and two pilot models were completed.
    (These were commandeered by U.S. army for shipment to the United States for further study.)

    The engine was built with supercharger and is air-cooled. The boost was 320mm of mercury and prodused 500 hp.
    The engines were to be used in the army's largest tank, the Type 4."

  3. Tier VII prem much? Could easily work with limited MM, and if the mobility is not quite enough, it could simply be given great terrain passability. -Platypusbill

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