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Thread: Home made manometer question.

  1. #1
    It's a way of life! oldnslow's Avatar
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    Home made manometer question.

    Going to make my own manometer out of tubing. Going to work on my 98 R1100RT. The question is, do the lengths of the tubes, that are above the liquid, running to 'carburetors', have to be of exact equal lengths? Or will vacuum not know the difference in the length?
    Mike Davis
    "Old n Slow" It's a way of life!
    1985 K100RT

    1998 R1100RT

  2. #2
    Registered User David13's Avatar
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    I don't know. And I don't need to know. As I have the widely touted Harmonizer. So I just take it out of the box, and hook it up, and balance.
    I know there are quite a few who like to stick with the old ways, so they perhaps can and will answer.
    I do shun some modern devices, sometimes, and go back to the ancient ways, for recreation.
    But maintenance on my bike is serious business to me, and I have fun doing it.
    dc

  3. #3
    IBA #44567 Ken F's Avatar
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    Mike,

    The one I made, I used about 5' of hose going up, and about 5'going into the loop & 5' back up. In other words 20' of tubing.
    The fluid will seek it's own level in the "loop" of tubing, and equalize. The vacume will pull the fluid to one side or the other, whichever has the most vacume.

    If you would like to call me, I've got one made that you are welcome to that already has the fluid in it!.
    .....or you would be welcome to use my Harmonizer if you would like...or both.

    Ken F
    IBA #44567 Pres. Springfield BMW Roadriders
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  4. #4
    It's a way of life! oldnslow's Avatar
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    I know there are electronic devices, but making the thing and showing my son how it works is part of the process. Plus, I get a kick out of 'old skool' stuff that works well!
    Mike Davis
    "Old n Slow" It's a way of life!
    1985 K100RT

    1998 R1100RT

  5. #5
    IBA #44567 Ken F's Avatar
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    Mike, I understand exactly what you are saying.
    Try this link, I think you will have a pretty good understanding.
    Ken

    http://www.powerchutes.com/manometer.asp
    IBA #44567 Pres. Springfield BMW Roadriders
    "Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe."
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  6. #6
    R100GS, '89 Guenther's Avatar
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    According to physics gas pressure is the same everywhere in an enclosed chamber.

    So unequal lengths of the tubes do not make a difference.

    /Guenther

  7. #7
    It's a way of life! oldnslow's Avatar
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    Quote Originally Posted by Guenther View Post
    According to physics gas pressure is the same everywhere in an enclosed chamber.

    So unequal lengths of the tubes do not make a difference.

    /Guenther
    Bingo! Thanks.
    Mike Davis
    "Old n Slow" It's a way of life!
    1985 K100RT

    1998 R1100RT

  8. #8
    Small road corner junkie pffog's Avatar
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    Quote Originally Posted by Guenther View Post
    According to physics gas pressure is the same everywhere in an enclosed chamber.

    So unequal lengths of the tubes do not make a difference.

    /Guenther
    What he said.
    2010 F800GS Full Ohlins package, '04 R1100S Replika
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  9. #9
    Long Range Rifleman
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    Quote Originally Posted by David13 View Post
    I don't know. And I don't need to know. As I have the widely touted Harmonizer. So I just take it out of the box, and hook it up, and balance.
    I know there are quite a few who like to stick with the old ways, so they perhaps can and will answer.
    Why did you even post this self aggrandizing drivel?

    The OP asked about tubing for a homemade manometer, not a braggadocios "I'm cooler than you" post.

    Jeeeeezus!

  10. #10
    Registered User jad01's Avatar
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    I've been thinking about this same homemade manometer idea, although I don't have a good educational reason- I'm just cheap... I think I'm going to try to make one of these manometers using bottles rather than the single tube full of fluid version:
    http://www.youtube.com/watch?v=GaTRyHxvneY
    http://www.youtube.com/watch?v=2PiQBr20kM8.

    I like the idea that the liquid in the manometer can't get sucked up into the carbs in this version (plus it looks way cooler!).
    Last edited by jad01; 12-26-2012 at 05:33 PM.
    Jim
    '78 R80/7 and '84 R100RS (Blues Brothers), '86 K75C (Icy Hot)
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  11. #11
    Tourmeister gr8ridn2's Avatar
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    The length of the tube to each throttle body does matter. While I don't argue against the physics mentioned, that is not the whole story. It is also matter of reading short vacuum pulses being applied to the balanced liquid or media. Unequal feeds will result in unequal readings in this application due to unequal timing. This is why BMW techs are advised to insure the lines to their factory balance instrument (sensitive to one millibar) are equal in length. I have seen results vary if the tubes are unequal from the equal length. It's just as easy to construct a manometer using equal length tubes to the throttle bodies, so I see no reason not to do this. I use water in my manometer and it has worked well and accurately for over 5 years. Have fun with your project!
    2013 R1200 GSW

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  12. #12
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    I made a two bottle manometer and it works great on my K75 and a friend's R80 and R1100.
    Ron

    91 K75RT ABS

  13. #13
    Registered User 36654's Avatar
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    Quote Originally Posted by Guenther View Post
    According to physics gas pressure is the same everywhere in an enclosed chamber.

    So unequal lengths of the tubes do not make a difference.

    /Guenther
    Since you're making a measure of an unsteady pressure, it would be preferable to have the tubes of equal length, as short as possible and restrict their moment. On small differential pressure measurements, tube vibration can be problematic due to the inertia of the fluid column.

    Typical test practice is to mount your transducer as close as possible to the measurement point.
    Cave contents: 99 R11RS, 2013 Toyota Tacoma, 03 Simplicity Legacy, 97 Stihl FS75, Dewalt DW625 & DW744

  14. #14
    Registered User 36654's Avatar
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    Quote Originally Posted by jad01 View Post
    I've been thinking about this same homemade manometer idea, although I don't have a good educational reason- I'm just cheap... I think I'm going to try to make one of these manometers using bottles rather than the single tube full of fluid version:
    http://www.youtube.com/watch?v=GaTRyHxvneY
    http://www.youtube.com/watch?v=2PiQBr20kM8.

    I like the idea that the liquid in the manometer can't get sucked up into the carbs in this version (plus it looks way cooler!).
    Cooler, perhaps, but also a much greater chance of leaks. I would go with a long loop of tubing and shorten to the required length.

    But, that's just me.

    BTW - 1 inch of Hg = 13.6-inches of Water. So, don't hook the manometer to only one intake unless you have a 25-ft tall loop. The intake vacuum could be on the order of 21 in of Hg or 10~11 psi.
    Cave contents: 99 R11RS, 2013 Toyota Tacoma, 03 Simplicity Legacy, 97 Stihl FS75, Dewalt DW625 & DW744

  15. #15
    Aspiring Profligate jeff488's Avatar
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    I made mine from about 20' of plastic tubing from Lowe's mounted with zip ties to a cool yellow aluminum yardstick.
    With center of the tubing at the bottom of the stick, the tubing runs up each side to the top of the stick and then to each throttle body.
    Tubing is filled with ATF, which is red and looks good with the yellow yardstick(very important).
    I hang it above the bike and there's about 7' of tubing to run to each TB.
    With the ATF level at the halfway point on the stick, there's time to correct the setting or shut the engine off to prevent the atf from going over the top, if the tb's are too far off.
    It's just a big U shape hung on a stick.
    Total cost; about 12.00 bucks.
    '04 Silver R1150RT "Big Oel"
    '08 Suzuki DL650 "Screaming Yellow Zonker"
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