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  1. #1
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    johan851's Avatar
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    Intake Restriction

    If you're trying to cut down on intake restriction in your pump, how big of a reservoir do you need right before the intake? I'm planning on doing a little bit of a modification to my Mag 3's intake, and stretching a tube over the outside of the inlet barb. I have some 3/4" ID Clearflex 60 that works just fine for this. Right before that, however, I'm going to adapt it down to a 1/2" hose barb. Is just increasing the intake size for the pump going to make a difference, or would I actually need a longer length of 3/4" tubing to make it worthwhile?

    Basically, if I could theoretically stretch 1/2" ID tubing over the inlet barb, would it increase flowrates at all?
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  2. #2
    Member LabRat23's Avatar
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    I am guessing that you just unscrewed the barb and intend to stretch a hose over the outside of the fitting.

    I have never done this, but if you could get the 1/2" tube to stretch over the inlet, you would see a difference. A lot of the backpressure in any system is caused by the blunt end of the barb that the water has to flow against. Eliminating that by stretching a hose over a fitting with a larger inside diameter than the hose does wonders. Pumps seem to respond very well to larger intakes. I would try it, since this doesn't necessitata a permanent mod. The worst that could happen is you would have to put the barb back on.

    I saw an article on this before. I'll try to find it for you.

  3. #3
    Member LabRat23's Avatar
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    Here is a link of the mcp350 mod. The mcp had a pretty bad flow restiction to begin with so I don't think your results will as good, but it does give you some idea of what can happen with better hose connections.

    http://www.systemcooling.com/mcp350_mod-01.html

  4. #4
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    Thanks for the link. So really the biggest factor is the diameter of the intake, not the availability of water in a low pressure environment like a reservoir?

    *EDIT* Yeah, really good review. That helps a lot.
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  5. #5
    Member kbtat2's Avatar
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    I did the mcp350 mod but I used a 1/2" to 3/8" fitting and it does work. The flow rate is quite a bit higher and my temps went down 2c. Not great but still better.

  6. #6
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    2C is still a pretty decent difference.
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  7. #7
    Member Craptacualr's Avatar
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    doing what you propose johan will increase your fowrate for 2 reasons... The first is because it will increase the diameter of the inlet. Just about all centrifugal pumps respond very favorably to increased inlet sizes. Remember, centrifugals can greate decent positve pressure, but very poor negative pressure, so increasing inlet diameter means more flow at that same low pressure.

    Also, putting a resevior right before the inlet to the pump very often increases fowrate as well. If the resevior is large enough and has a thin layer of air in it, the water there helps add head pressure to the system if the inlet of the pump is at the BOTTOM of the resevior. The fluid dynamics of such a proposal are very complicated, but generally speaking a resevior with a top-down surface area of at least 4 square inches with the inlet pump fitting at the bottom will increase your fowrate. How much is nearly impossible to predict, and more importantly, would the increase be cost-effective? Another difficult question. My vote would be for no, it's not cost/time effective, but thats just me.

    Remember, that if you use or create a poor resevior you can actually decrease your flowrate by causing more restriction at the pump inlet...

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