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D.I.Y. Manometer.

Discussion in 'Chat & Tech Info' started by Charlie J, Oct 26, 2010.

  1. Charlie J

    Charlie J Cruisin' Guzzisti

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    I have looked on these forums (but obviously not in the right spot) for articles on home made manometers,regarding conversion of inches vacuum (mercury)to whatever fluid you may use in your own. If the specific gravity of Mercury is 13.56 and the specific gravity of Auto Trans Fluid is 0.87 ,does that mean that 1 centimetre of mercury is equal to 15.6 (13.56 divided by 0.87) centimetres of Auto Trans Fluid ?
     
  2. Mike.C

    Mike.C GT Reference

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    Um not sure why you would want to know, other than intellectual interest which of course is a noble pursuit. If you make a manometer for balancing the throttle bodies, it works by comparing the level in the two tubes that are joined in a "U" fashion, the vaccum in one "fights" against the vaccum in the other and when the two are equal equlaibrium reigns and the columns will be level and the TB's are in sync.

    Here are some tips on building one. Start with a 6m length of high quality pvc tube. Cut it in half exactly and re-join it with a Tee junction at the bottom of the loop. Fit a short silicone tube with blanking screw onto the Tee and use this for filling with oil using a syringe. Clip the tubes to the front of a board, loop them over the top and clip them about 2/3 of the way down the back. Fit a small length of silicone tube into the ends of the tubes where they will fit onto the take-off nipples, which get too hot for pvc tubing to stay tight. (I use left over model aeroplane engine fuel silicone tubing which also comes in handy when bleeding brake and clutch nipples too.)
     
  3. DanPez

    DanPez Cruisin' Guzzisti

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  4. Charlie J

    Charlie J Cruisin' Guzzisti

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    I was just curious as to the difference. Id made my first manonmeter out of 6 mm clear plastic hose and 2 drilled cap screws but the manometer showed weird vacuum bias. So I made another one.stiffer hose, a tee for filling and used engine oil (not used engine oil)for a medium. But bugga me if that one didnt show weird stuff happening too. So guess what, I made another one. Off to Pirtek (a hydraulic hose company) I went and bought some 6x4 mm PVC hose a "quick fit "Tee and plug and 2 M6 screw in "quick fit " fittings. I used ATF,painted the backing board white,marked a zero point and increments of 10 mm above and below zero to 350 mm.The screw in fittings have a bore of about 1.5 mm. This looks all very resplendant, does not leak, is quick to fit and hang above my bike but it shows strange happenings as well!!!! Maybe I should buy a digital one
     
  5. Kevin.NZ

    Kevin.NZ Cruisin' Guzzisti

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  6. DanPez

    DanPez Cruisin' Guzzisti

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    One thing for sure that will cause irratic values ...... whether liquid U-tube or digital.
    Vacumm Leaks
    Fitting / Connections have to be well tight.
     
  7. Kevin.NZ

    Kevin.NZ Cruisin' Guzzisti

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    With the 1st one I made, where the plastic pipes connected to the throttle body they got hot and softened and the engine vacuum caused them to close up giving dodgy reading so I joined the plastic pipe to a 50mm length of firm hose to put like a thermal barrier there.
    Kevin
     
  8. Mike.C

    Mike.C GT Reference

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    If you use a short length of model aeroplane silicone fuel tubing between the throttle body nipple and the manometer tube it will not pop off with heat.

    Ask for the thick walled stuff, not all hoby shops keep the thicker walled version. As always the cheap stuff is so thin walled that it easily pops off with a bit of sideways twist if the manomenter tubes put a bit of weight on them.
     
  9. Charlie J

    Charlie J Cruisin' Guzzisti

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    My manometer does not leak. The quick fit fittings use an O ring on the thread and jaws to clamp the outside of the hose. I hang the gauge above the back of the bike and it does not move arond. I have also swapped sides with the hoses and get the same readings. There are no vacum leaks/air leaks on the inlet side,verified with ether in an aerosol. I dont let engine temp get over 90 degrees C
     

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