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Thread: Joining small diameter pipe

  1. #1
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    Joining small diameter pipe

    I want to make some exhaust gas backpressure measurements, and plan on connecting to the exhaust via existing O2 bungs.

    From what I've seen, people do this by attaching a length of brake pipe or similar to a blanking plug that sits in place of the O2 sensor. The question is, how to join the pipe to the blanking plug? The EGT runs at up to 800 degrees 50mm out from the head, so I'm not sure if brazing is an option. I don't have a TIG.

    I was thinking maybe a normal brake pipe and nut, but I would need to have a nipple inside the bung for the flared bit of pipe to push onto, and that's probably beyond my machining skills.

    Any suggestions?

  2. #2
    . crack's Avatar
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    just cut the steel fitting of a brake hose / cut up a steel t-piece / ect. and pay the man to tig it on

  3. #3
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    Quote Originally Posted by crack View Post
    just cut the steel fitting of a brake hose / cut up a steel t-piece / ect. and pay the man to tig it on
    You, Sir, are a genius. In fact I could weld a fitting that big myself with the MIG.

  4. #4
    are hairy Dogsballs's Avatar
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    Buy o2 bung drill and tap 1/8", then screw in cut up brake hose
    Quote Originally Posted by 50RTD View Post
    Dave, have you uploaded the data from the carby?

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    Quote Originally Posted by Dogsballs View Post
    Buy o2 bung drill and tap 1/8", then screw in cut up brake hose
    Thanks Dogsballs, I had considered this, but I'm not convinced a brake hose is going to withstand the heat. I think this is why others use a length of pipe, to give the heat a chance to dissipate.

  6. #6
    are hairy Dogsballs's Avatar
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    O2 bungs should be down a bit off the header

    How you going to measure pressure? Won't that get effected by heat as well
    Quote Originally Posted by 50RTD View Post
    Dave, have you uploaded the data from the carby?

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    The bung hole I want to use is the one I welded in for the wide band, it's about 300mm from the head.

    I've got a spare 1 bar MAP sensor, I was going to run some vacuum hose into it, then connect it to the data logger. I figured that because the exhaust gas isn't actually flowing through it, if the pipe and vacuum hose are long enough it shouldn't get heat affected. If that doesn't work I'll hook up a guage, which is what others seem to do.

  8. #8
    Non Compos Mentos Gammaboy's Avatar
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    Knock the porcelain and centre electrode out of a sparkplug, weld tube into that.
    "Where can we get hold of a Vincent Black Shadow?" "Whats that?" "A fantastic bike," I said. "The new model is something like two thousand cubic inches, developing two hundred brake-horsepower at four thousand revolutions per minute on a magnesium frame with two styrofoam seats and a total curb weight of exactly two hundred pounds."

  9. #9
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    Why don't you buy the correct fitting with an olive and buy the correct size pipe and a flaring tool? flaring tools from china are very cheap.
    Quote Originally Posted by Lord_fahrquhar View Post
    The au put the fucking tunnel in with the bullbar. Even Chuck Norris respects the ability of the au coon.

  10. #10
    Non Compos Mentos Gammaboy's Avatar
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    Quote Originally Posted by Rdyno View Post
    Why don't you buy the correct fitting with an olive and buy the correct size pipe and a flaring tool? flaring tools from china are very cheap.
    Because a fucked spark plug and some welding wire is cheaper?
    "Where can we get hold of a Vincent Black Shadow?" "Whats that?" "A fantastic bike," I said. "The new model is something like two thousand cubic inches, developing two hundred brake-horsepower at four thousand revolutions per minute on a magnesium frame with two styrofoam seats and a total curb weight of exactly two hundred pounds."

  11. #11
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    Way it's been done in the past, AN sleeve and tube nuts, 37* flares, several feet of stainless tube - coiled so it's not half over the engine bay - MSCN should have annealed stuff to make that easier.

    Something to go into a 18 x 1.5 bung shouldn't be too hard. Honeywell have something that might be better than running vacuum hose to a MAP sensor off some sort of nipple...no doubt npt though!

  12. #12
    Registered User Euronymous's Avatar
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    What about, cut a section of steel line, run a die over one end, and then tap the o2 bung the same and just screw the line in. Can ad a few nuts to lock it in place if required?

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