Il-2 Sturmovik
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Thread: Il-2 Sturmovik

  1. #1
    Hello folks,
    I prefer to separate the Il-2 Sturmovik thread from the other Russian aircraft Im
    planning to build, so Ill use this thread for it as soon as I start building it.

    At the moment Im preparing the .air file, and I seem to be having trouble with
    the single speed supercharger, probably because of the information quoted in
    the source I found may not be exact, or my interpretation of it may be wrong.

    For non-WEP values of 47.2 inches of mercury, the models performance curve
    tallies acceptably with
    specifications, even with the lower performance of
    900 Hp at 16000 ft.


    However, as soon as I enter the extra 6.3 in. Hg WEP boost, for the full 53.54 MP
    that the supercharger gave, the models performance goes way above
    realistic
    values, by more than 50 Hp at S.L. and more than 300 Hp at 16000 ft.

    At 2500 ft there should be 1720 Hp at 2350 RPM, with full boost, but far too much
    comes out. Then, with 47.2 in. Hg boost, I get the correct 1500 Hp, but not at
    2050 RPM - that stays at 2350 RPM, but I recall its difficult to deal with.

    At the moment Im trying out different Boost values to see where the correct
    boost-perfomance lies. Correcting WEP Boost MP to get rid of the 50 Hp difference
    at low altitude, still leaves it at over 200 Hp too fast at altitude. This doesnt sound
    new, and I seem to remember something similar happening before on some older work,
    and in some posts it was mentioned that a compromise must be reached.

    I wonder how complicated it will get with the other Russian plane, with the 2-speed
    supercharger. That will probably be even more difficult, but Ill deal with it when
    the time comes
    .

    Anyway.... more later!
    Cheers,
    Aleatorylamp
    Last edited by aleatorylamp; May 14th, 2018 at 14:52.

  2. #2

    Record 505 Emergency Power Change Rate (Minimum 0.528 ???)

    Hello Folks,
    The obscure Emergency Power Change Rate parameter does have some useful effects.
    There is a comment in AirEd that it should be set to a minimum of 0.528, but in some
    cases it can be completely misleading, probably for low Boost Gain values.

    Max. Manifold Pressure is set at 47.2, WEP Manifold Pressure is set at 6.3, and normal
    Supercharger Boost Gain is at 1.835.

    This gives me the desired non-WEP power of 900 Hp at 16000 ft, the desired non-WEP 1500 Hp at 2500 ft and the desired WEP 1720 Hp at 2500 ft.


    Now, if the Parameter in question is set to the commented minimum of 0.528, it causes an ever growing undesired increase in WEP power at altitude. At 10000 ft I was getting an excess of 360 Hp for WEP!

    It appears that this Parameter exists to avoid this.
    Trying out different values, Ive got it at 0.178 now, and I am getting a much more realistic 16000 ft WEP power of 1017 Hp. It has also corrected the excess WEP power at most of the lower heights, down to 6500 ft. Further below values remain expectedly closer to the 1500 non-WEP and the 1700 WEP Hp.

    I thought this was very interesting indeed!
    Cheers,
    Aleatorylamp
    "Why make it simple if you can also make it complicated?"

  3. #3
    Hello all!
    I was fine tuning the Mikulin AM38F engine this morning, and
    came up with some very satisfactory results:

    Aim:
    S.L. : 1720 Hp at 2350 RPM and 53.53 in. Hg MP
    2500 ft: 1500 Hp at 2050 RPM and 47.24 in. Hg MP

    Reference:
    Mikulin engine power chart. The orange lines refer to the AM38F engine.
    The WEP line overlaps with the red line of the AM38 engine.

    Performance results, all at 2348 RPM:
    S.L.:
    1718 Hp 248 mph 53.5 MP Hp OK!
    1472 Hp 238 mph 47.2 MP Hp OK!

    2460 ft:
    1747 Hp 259.5 mph 53.5 MP Hp +2.5 mph
    1498 Hp 242.2 mph 47.2 MP Hp v.g!

    3280 ft: (1000 m)
    1708 Hp 258.4 mph 52.2 MP +88 Hp
    1509 Hp 244.0 mph 47.2 MP +59 Hp

    6560 ft: (2000 m)
    1509 Hp 252.3 mph 46.1 MP +209 Hp
    1343 Hp 242.1 mph 42.2 MP +183 Hp

    10000 ft: (3000 m)
    1316 Hp 247.1 mph 40.3 MP Hp OK!
    1167 Hp 238.8 mph 36.8 MP Hp v.g!

    13100 ft: (4000 m)
    1156 Hp 242.4 mph 35.7 MP Hp v.g!
    1021 Hp 235.3 mph 32.5 MP Hp v.g!

    15800 ft: (4800 m)
    1029 Hp 238.2 mph 32.0 MP Hp v.g!
    906 Hp 206.5 mph 29.2 MP Hp v.g!

    19000 ft: (5800 m)
    890 Hp 222.3 mph 28.2 MP Hp OK
    781 Hp 192.2 mph 25.7 MP Hp OK

    Probably not too bad...
    Cheers,
    Aleatorylamp
    Attached Thumbnails Attached Thumbnails mikulin-engines.jpg  
    "Why make it simple if you can also make it complicated?"

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