I-211 / Mig-9E - Very Questionable Performance

[Laurelix]

Everywhere I look… it says
670km/h at 7,100m and that it's powered by M-82F engine

I have many issues with believing this…

Let's begin with I-210 which is also a Mig-3 but not aerodynamically refined like the I-211 was. It's powered by M-82A engine which has same engine power as M-82F, the difference being it can't use 1700hp continuously and is mostly limited to 1400hp but the engine power curve is identical and both engines do not have "WEP" past altitude of around 3500m.

I-210 is rated
475km/h at Sea Level - 1400hp
507km/h at Sea Level - 1700hp
565km/h at ~6000m

I-211 top speed is rated at 7,100m when M-82A / M-82F engines are usually rated to achieve top speed at 5800-6200m is my first issue. Second issue is that M-82F powered planes have roughly 58km/h difference between sea level and optimal altitude… etc La-5F with 561km/h at SL , 619km/h at 5800m… if I-211 had 670km/h at optimal altitude, that would roughly translate to roughly 612km/h at sea level max speed for I-211 which seems absurd to me when the I-210 with same 1700hp engine power can only do 507km/h at Sea Level.

What's more is that the inline engine and aerodynamically refined Mig-3 also known as I-230 or Mig-3U is rated to achieve 505km/h at Sea Level with 1350hp.
1700 / 1350 = 1.25926
Cube Rooted = 1.07987
505 x 1.07987 = 545km/h

So basically even a aerodynamically refined Mig-3 with inline engine would only be capable of 545km/h at SL with 1700hp, never mind doing 612km/h at SL

Realistically what I would estimate for I-211 with M-82F engine would be around
545km/h at SL
603km/h at 5800m

Edit…
Unless the I-211 airframe was made so clean that it has La-7 equivalent drag since both planes have similar wing area and roughly same type of engine. Then 670km/h at ~6000m could be possible

 

[wells]

Gordon and Khazanov, on pg 74, say the I-211 had a boosted engine, compared to the MiG-9. Start there. If the flight test data doesn't make sense, you probably don't have all the data, and neither do I.

The question that needs to be answered, is "How was the engine boosted?" Because, it must have been to achieve 670 km/h @ 7000 m and climb to 5000m in 4.0 min. I'll see what else I can find....

 

[bf109xxl]

The major difference between the M-82F and M-82FN was the fuel system: the first was equipped with a carburetor, while the second used direct injection. Theoretically they should have the same altitude performance, but in practice the carburetor worked abominably and caused up to 10% power loss (usually much lower).
The I-211 ("E") had modified design of the cowling and oil coolers in comparison with the MiG-9, in addition, the I-211 was lighter by 300 kg. Only its small combat load - only 390 kg for ammunition and fuel - is questionable, but not its flight performance. It was slightly better than that of the La-7 due to a more advanced design with less aerodynamic drag. The mentioned book by Gordon and Khazanov has good photos demonstrating the careful finishing of the I-211("E").