Testing QEVs

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  • Trbo323
    MCB Member
    • Jul 2020
    • 6358
    • Vancouver WA
    #1

    Testing QEVs

    Ok. Bit of an odd scenario here.

    For a while my cocker has not been happy. Mq2 valve, e2, resurrection ram and eclipse QEVs, the cube style ones not the rectangular ones are the highlights that likely pertain to this situation.

    What happens is when you get after the trigger it starts stumbling and has massive shoot down. Single shot it's fine but it won't manage anything over about 6bps or every shot is at 100fps at best. You can really clearly hear it as well, it's like shooting with a barrel swab in the barrel. You didn't even have to have paint in it, dry firing you can hear it as well

    At first I thought it was the timing, went all over chasing it but it doesn't matter what I do it won't shoot above 6ish bps. So I started wondering if it could be the QEVs. Pulled them off tonight and I'm thinking they are the problem, if I blow into them they seem really stiff, not flowing well and I'm not sure they are exhausting either.

    When I got these I had to pull them apart to switch the input and exhaust sides for my build, long story, but I'm wondering now, are both ends just screwed in all the way or are they supposed to maybe be gapped back a bit to allow the diaphragm to move?

    Can anyone think of a good way to test them?

    Thanks in advance

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    • flyweightnate
      MCB Member
      • Jul 2020
      • 1853
      • Dallas, TX
      #2
      Leave them off and see if it runs better without them?

      It sounds more like you're starving the gun. What reg, how much volume up front, what's your tank pressure? MQs can be very thirsty, and it depends a lot on pressures, tolerances, and dwell.
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        • Trbo323
          MCB Member
          • Jul 2020
          • 6358
          • Vancouver WA
          #3
          Originally posted by flyweightnate
          Leave them off and see if it runs better without them?

          It sounds more like you're starving the gun. What reg, how much volume up front, what's your tank pressure? MQs can be very thirsty, and it depends a lot on pressures, tolerances, and dwell.
          Oh I'm aware. But I've had it running fine in the past with very similar parts on board. I actually had a customers marker before that ran a mq2 with the exact problem you are talking about but in his case he was running it mini ed and the result was it would not shoot above 260 at any point

          It's hard to describe the sound it makes but I'm about 95% sure it's firing with the bolt half closed when this pops up

          Karni front block so I've actually extended the front grip out, cp v2 hpr, ram is from a resurrection, jackhammer 2 lpr

          Son 4ms

          I forget the rest of it right now, like I said though I've been all over the timing map and nothing changes this issue

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            • flyweightnate
              MCB Member
              • Jul 2020
              • 1853
              • Dallas, TX
              #4
              In that case, the test is to push air through the inlet, and see where it comes out "most naturally". Then push air through the outlet and see where it wants to come out. Inlet should dump to outlet, outlet should dump to vent.

              I'd run an LPR to the inlet, and leave hoses off.
              Then, barb the LPR abs run it to the QEV outlet, and see if it wants to come out the inlet or the vent.

              Personally, I never ran any autococker fast enough to benefit meaningfully from the QEVs. Used them anyways...
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                • Trbo323
                  MCB Member
                  • Jul 2020
                  • 6358
                  • Vancouver WA
                  #5
                  Originally posted by flyweightnate
                  In that case, the test is to push air through the inlet, and see where it comes out "most naturally". Then push air through the outlet and see where it wants to come out. Inlet should dump to outlet, outlet should dump to vent.

                  I'd run an LPR to the inlet, and leave hoses off.
                  Then, barb the LPR abs run it to the QEV outlet, and see if it wants to come out the inlet or the vent.

                  Personally, I never ran any autococker fast enough to benefit meaningfully from the QEVs. Used them anyways...
                  For this build I decided to run my front block hoses over the top of the barrel rather than under it so there's about double the hose length that needs to be vented, hence the QEVs. I may try going without them and see what happens first though

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                    • Trbo323
                      MCB Member
                      • Jul 2020
                      • 6358
                      • Vancouver WA
                      #6
                      Ok. Took the QEVs off today and ran without them, can confirm they are the problem. They are slowing down the ram.

                      So what's up? I've taken them apart, the diaphragms look fine, I even had a second qev I took apart and swapped in the diaphragm from it to check and no change.

                      My best guess at this point is the two "sides" to the qev (the hose from the noid and the exhaust side) are too close to each other and not allowing the diaphragm to move as much as it should. If that is the case I'm not really sure how to get the "correct" spacing.

                      The diaphragm is the only thing inside right? I wouldn't be missing any parts

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