N/A Help

Discussion in 'PSI Superchargers Tech Questions' started by spitzerscott, Apr 4, 2012.

  1. spitzerscott

    spitzerscott Member

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    I read and hear alot about Water Grains Per Pound of air. Is this something I need to consider with a normally aspirated injected engine or is this for the blown engines? Thanks, Scott
     
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    spitzerscott, Apr 4, 2012
  2. Mike Canter

    Mike Canter Top Dragster
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    It is important to all type of motors except nitrous. We had a water grain count of 113 at ADRL in Houston this past weekend. Not much you can do other than increase the compression or advance the timing. The water molecules take up all the room so you have a hard time filling the air with atomized fuel. If I read Patrick Hale's great book, Motorsports Standard Atomospheres And Weather Correction Methods, it also lessens the cooling ability of the alcohol. To use Patrick's example of swamp coolers...they do not work in a wet, humid climate.
     
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    Last edited: Apr 4, 2012
    Mike Canter, Apr 4, 2012
  3. WANNABE

    WANNABE New Member

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    With a general N/A engine, you really can follow either. Water grains or relative humidity. And you just need to know that when the water is in the air, you need to start the spark earlier. More water, more advance. And there really isn't much more that you can do. But once you know where your engine likes to be at different amounts of water in the air, you are set. It is really not rocket science.
    If you get WAY into it, you can start to look at both, but that is like pro stock stuff where one thou=a mile!
     
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    WANNABE, Apr 4, 2012
  4. Mike Canter

    Mike Canter Top Dragster
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    Just to make sure there is no confusion here. Relative Humidity is different from Water Grain Content.
     
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    Mike Canter, Apr 5, 2012
  5. spitzerscott

    spitzerscott Member

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    Thanks Mike and Wannabe, I was hoping for my mild set-up I could just go with Relative Humidity as I can measure that with what I have. Just wondering, what do you need to measure Water Grains per Pound? Thanks again for your help Mike. Scott
     
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    spitzerscott, Apr 5, 2012
  6. Mike Canter

    Mike Canter Top Dragster
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    I use Davenport's Jetsize Software but somewhere I have the formula. If I remeber correctly it is too complicated to work simply at the track unless you program a spread sheet. You only need to worry about water grains if they are over 100. I know that the Computech RaceAir Weather station calculates it also.
     
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    Last edited: Apr 5, 2012
    Mike Canter, Apr 5, 2012
  7. WANNABE

    WANNABE New Member

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    The nicer weather stations will give you water grains.
    But there is so little you can do with a standard N/A engine to account for it, it is really not worth chasing it too far. (We don't slap different rod lengths in between runs, or head gasket thicknesses, fuel percentages, etc. Pretty much what we've got is what we've got.)
    Relative humidity IS different from water grains, but is much more available with inexpensive weather stations. But just choose which you want to follow and get a general adjustment on your tune-up for that and follow it.
     
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    WANNABE, Apr 6, 2012

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