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  1. #1
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    Improving the Howerton Silicone Meth Bung

    So after using one last year, I swear my WGDC increased by 6-10%, giving me a small boost leak. Maybe it didn't, but I wanted to create a better seal anyway. A gap is seen in the picture below.

    Click here to enlarge

    I purchased weld bungs, only to find that there is no appropriate location on my Helix V1. A custom up-pipe also proved challenging due to spacial constraints.

    So I designed some couplers to secure the bung outward, while simultaneously preloading the bung against the silicone to seal any boost leak. It was two semi-circular halves which also formed to the 2.5" silicone. So there I was in the machine shop, and after about 10 minutes on the mill, I saw the end of the ballscrew and then it struck me. I'll let the picture speak for itself.

    Click here to enlarge

    5/8" e-type circlip. 0.048" thick, just enough to take up the slack.

    As a sidenote, I'm sure the full pin clip would work as well, but I didn't have any around.

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    I wonder why they didn't design the bung in two pieces, with each piece having threads such that the two halves clamp the silicone coupler.

    I like you solution though, simple and cheap. Have you thought about putting some rtv under the lip on the inside, or do you think the force of the inner lip against the inside of the coupler is good enough? Guess it would be easy enough to test.
    Eppur si muove.

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    The bungs come in various sizes for various silicone hose wall thicknesses. What looks to have happened here is you may have used a 5mm bung on a 4mm thick silicone coupler. Possible? It'd make sense to me as 0.048" of your spacer is 1.2mm which would explain why it'd seal better.
    Click here to enlarge

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    Click here to enlarge Originally Posted by ajm8127 Click here to enlarge
    I wonder why they didn't design the bung in two pieces, with each piece having threads such that the two halves clamp the silicone coupler.
    Imagine what would happen if the bung pieces would loosen...your engine would swallow one of the pieces and it would be destroyed.

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    Click here to enlarge Originally Posted by cstavaru Click here to enlarge
    Imagine what would happen if the bung pieces would loosen...your engine would swallow one of the pieces and it would be destroyed.
    Loctite 242.

    The thread diameter would be around 3/4" to 1". If you put Loctite on the threads, the bung would never come lose by itself. I imagine it would be difficult to remove period. You would want to design the bung so a wrench or socket could be placed on either half to remove it.
    Eppur si muove.

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    Using RTV is not ideal since I'd rather minimize the amount of material that has the potential to be ingested into the engine.

    @dzenno, No, this is the 4mm bung. It sits okay by itself, but the problem is that not all silicone couplers have an even thickness all around, combined with wear on the coupler itself and a narrow top securing diamater for the bung.

    To get that clearance on top of the bung, you have to push from the back. Since the back is tapered, it only seals better. Hell for less than $0.50, why not.

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    Click here to enlarge Originally Posted by Tzu Click here to enlarge
    Using RTV is not ideal since I'd rather minimize the amount of material that has the potential to be ingested into the engine.

    @dzen no, No, this is the 4mm bung. It sits okay by itself, but the problem is that not all silicone couplers have an even thickness all around, combined with wear on the coupler itself and a narrow top securing diamater for the bung.

    To get that clearance on top of the bung, you have to push from the back. Since the back is tapered, it only seals better. Hell for less than $0.50, why not.
    Ok, makes sense. I'll bring this up with Howerton. You're sure this isn't 3mm thick silicone? Have a way of measuring it with a caliper?
    Click here to enlarge

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    Click here to enlarge Originally Posted by Tzu Click here to enlarge
    Using RTV is not ideal since I'd rather minimize the amount of material that has the potential to be ingested into the engine.
    RTV is one of those things that is in no way better if you apply more. The proper amount would not be squeezed out forming a bead that could be sucked up. An o-ring with a soft durometer would be another option, but it may not be necessary due to the coupler itself being so soft. McMaster has some with a durometer of 50A. Just things to think about if you encounter future leaks.
    Eppur si muove.

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    @dzenno I can measure over the weekend. I did measure the section at the IC connection, and it varied from 3.5 to 5mm. It's a contributor to the cause no doubt.

    @ajm8127, the real solution would be welded bungs. I'm still looking into it as an option. As long as my WGDC isnt not increased, this solution is all gravy.

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    @Tzu, I've checked with Howerton. He says he doesn't remember making that bung in that color and it looks to be a 5mm bung. It'd be good to check both I guess. FWIW I've used these on my installs as well as my own car a number of times without issues but if that silicone hose varies that much in thickness I guess it could use some additional support on the outside like you've done. Don't see anything wrong with that as long as its on the outside.
    Click here to enlarge

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    I don't know, I ordered one a year or two ago and it was light blue, and I ordered another one about 2 months ago and it was silver. Both are 3.4mm working length for 4mm tubing. The variable for my situation was the thickness of the silicone, which was closer to 3.3mm instead of the advertised 4mm.

    To further my original post, here is a silver 4mm meth bung with an e-clip on it which slipped on just fine. The e-clip is black, on the bottom bung.

    Click here to enlarge

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    Click here to enlarge Originally Posted by Tzu Click here to enlarge
    I don't know, I ordered one a year or two ago and it was light blue, and I ordered another one about 2 months ago and it was silver. Both are 3.4mm working length for 4mm tubing. The variable for my situation was the thickness of the silicone, which was closer to 3.3mm instead of the advertised 4mm.

    To further my original post, here is a silver 4mm meth bung with an e-clip on it which slipped on just fine. The e-clip is black, on the bottom bung.

    Click here to enlarge
    What size jets are you running? HFS-4?
    2008 135 GIAC Stage II Race File
    2011 335d Stock

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    Click here to enlarge Originally Posted by Tzu Click here to enlarge
    I don't know, I ordered one a year or two ago and it was light blue, and I ordered another one about 2 months ago and it was silver. Both are 3.4mm working length for 4mm tubing. The variable for my situation was the thickness of the silicone, which was closer to 3.3mm instead of the advertised 4mm.
    Did your fuel trims improve with the new nozzle location? I'm gearing up to move mine in a couple of weeks.

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    Click here to enlarge Originally Posted by Edogg218 Click here to enlarge
    What size jets are you running? HFS-4?
    Modified PWM kit, which is essentially an HFS3.

    Click here to enlarge Originally Posted by DCAFS Click here to enlarge
    Did your fuel trims improve with the new nozzle location? I'm gearing up to move mine in a couple of weeks.
    Still doing testing. I lost about 50-70 ml/min due to the check valve. Trunk mount tank also introduced high line losses, also reducing flow. Ask me in a week or so and I'll have some better data. I'm on a low boost map right now for initial testing.

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