ATA in Inches Hg

Discussion in 'Engines' started by Ivan1GFP, Nov 4, 2010.

  1. Ivan1GFP

    Ivan1GFP Member

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    Hello All,

    This issue has confused me for a while:

    What is the conversion from German ATA manifold pressure settings to American Inches Hg?

    Thanks.
    - Ivan.
     
  2. Shortround6

    Shortround6 Well-Known Member

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    Roughly 30 in Hg = 1.0 ATA so 42 in HG would equal 1.4 ATA.

    British measured in pounds of boost above sea level Atmospheric pressure. Sea level pressure being 14.7lbs or rounded off to 15lbs. so 6lbs of boost is equal to 21lbs total pressure or 42in Hg or 1.4 ATA.

    Again, roughly with some decimals rounded up. :)
     
  3. Ivan1GFP

    Ivan1GFP Member

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    Hi Shortround6,

    I actually need a much more precise number than this.

    I believe the number is around 28.8 to 29.2 but don't know the exact conversion or why.

    The British measure in pounds boost above 14.696 pounds.
    The Americans measure in absolute pressure inches of Mercury.
    The Japanese measure in mm Mercury above 760 mm.

    The Germans measure in multiples of Atmospheric Absolute pressure but I don't know what their base number for 1.0 ATA is. I know it isn't 760 mm because the conversions don't work out for the values I have found listed.

    - Ivan.
     
  4. jerryw

    jerryw Member

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    Ivan1,
    Standard Atmos. Press at Sea Level is:
    760 mm Hg at 0 degC
    29.921 ins Hg at 0 degC
    14.696 lb/sq in.
    So, 1 ata is any one of these.

    Can you give us some examples of the conversions you have found that don't convert?
     
  5. jerryw

    jerryw Member

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    Ivan1,
    Standard Atmos. Press at Sea Level is:
    760 mm Hg at 0 degC
    29.921 ins Hg at 0 degC
    14.696 lb/sq in.
    So, 1 ata is any one of these.

    Can you give us some examples of the conversions you have found that don't convert?
     
  6. krieghund

    krieghund Member

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    Here is a equivalent boost pressure chart from my TAIC manual
     

    Attached Files:

  7. Ivan1GFP

    Ivan1GFP Member

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    Hi Krieghund,

    Thanks for the chart, Very useful, though I will still need a number to do som mathematical conversions. I can estimate very well with this chart though.

    Hi JerryW,
    Krieghund's chart pretty much illustrates what I was asking about.

    - Ivan.
     
  8. Milosh

    Milosh Well-Known Member

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    1 ATA = 14.223psi
     
  9. Ivan1GFP

    Ivan1GFP Member

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    #9 Ivan1GFP, Nov 5, 2010
    Last edited: Nov 5, 2010
    Is there a metric value equivalent? I figure if this is used by the Germans, they must have based it on some metric value.
    This looks to be very close to 1 kg / cm^2.

    - Ivan.
     
  10. Milosh

    Milosh Well-Known Member

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  11. Ivan1GFP

    Ivan1GFP Member

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    Next Question:

    Why doesn't this match up with the chart that Krieghund posted?

    - Ivan.
     
  12. mikewint

    mikewint Well-Known Member

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    #12 mikewint, Nov 5, 2010
    Last edited: Nov 5, 2010
    1 atmosphere is 14.69583 pounds per square inch or 101.325 kilo Pascals or 1033.21910 grams per square centimeter or 760 mm of Hg or 760 Torr of pressure. The Bar is equal to 100 kPa so it is almost 1 atmosphere. it is off by 1.325 kPa or 9.938317 torr or mm of Hg. Since an English inch is 2.54 cm 760mm of Hg is 29.92125984 inches of Hg. do these give you enough accuracy?
     
  13. Ivan1GFP

    Ivan1GFP Member

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    Hi Mikewint,

    Precision wasn't the last question. I already wrote up a spreadsheet since Milosh's first post. By my spreadsheet (and calculator), 1.00 ATA should be 29.06 inches Mercury. If you look at Krieghund's chart, the number looks to be slightly UNDER 29.0 inches. I was wondering why that was the case. I tried out a few other numbers. They're all fairly close, but the conversion factor here doesn't quite seem to agree with the chart that was posted.

    Perhaps the chart is incorrect??? One or the other must be incorrect. I don't know which and that is why I am asking.

    - Ivan.
     
  14. vintage radials

    vintage radials New Member

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    Temp should be warmer, around 59 F for standard day with inches of Mercury HG, and I think the chart might not have the temp included. Or temp might be included for some but not all. I always get air temp alt when we are checking power to air speed to correct for density altitude.
     
  15. wells

    wells Member

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    German ata may have been measured in bars,

    1 atm = 101.3 kPa
    1 bar = 100 kPa

    Therefore,

    1 atm = 1.013 bar

    or

    1 bar = 0.987 atm
     
  16. Ivan1GFP

    Ivan1GFP Member

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    #16 Ivan1GFP, Nov 5, 2010
    Last edited: Nov 5, 2010
    Playing with units for conversion is always fun.

    If we measure everything in Torr, we have
    1 ATA = 735.56 Torr
    1 atm = 760 Torr
    1 bar = 750.06 Torr

    With these conversions, these values show that 1 ATA is greater than it appears on the TAIC table that Krieghund posted. That means to agree with the TAIC table, 1 ATA is somewhere UNDER 753.56 Torr....
    If it were equal to 1 bar, it would be even larger, so the correlation would be even worse.

    - Ivan.
     
  17. BikerBabe

    BikerBabe Active Member

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    1 ATA = 14.7 PSI = 760 mm/hg = 1.01 Bar.
    Was that any help?
     
  18. Ivan1GFP

    Ivan1GFP Member

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    Hi BikerBabe,

    From prior posts, we already know that is inaccurate. Look at Krieghund's posted table. So far the closest is 1 kg/cm^2 and even that seems a bit high.

    - Ivan.
     
  19. BikerBabe

    BikerBabe Active Member

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    Okay :lol: Sorry, I didn't bother to check the data, it's "something with numbers". :p
     
  20. mikewint

    mikewint Well-Known Member

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    #20 mikewint, Nov 8, 2010
    Last edited: Nov 9, 2010
    Ivan,
    The ATA (Technische Absolut Atmosphare) was designed so that 1 ATA or at = 1 kilogram per 1 centimeter squared. which is an incorrect unit since pressure is defined as FORCE per unit of area and kilogram is a mass unit. Nonetheless it is convertible to other pressure units:

    1 at = 1 kg/cm squared
    = 14.223343307119565 pounds per square inch
    = 0.9678411053540588 atm or standard atmosphere
    = 28.95902519867009 inches of Hg (0 degrees Celsius)
    = 735.5592400690826 Torr or mm of Hg

    I would not expect a printed chart to be as accurate as a mathematical conversion since printing registers could be off.
    mike
     
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