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Why does a high CFM 140mm fan on my CPU heatsink increase my CPU temps

As the name of the thread states, I am baffled by the effects of placing a 140mm fan on my heatsink. I used to use a CM R4 (120mm "90"CFM version) and when I replaced it with a Yate Loon D14SH-12 the Average temp rose about 2-3 degrees. The heatsink is a Venomous X Black in push pull configuration.

Could someone explain to me this. It doesnt make sense that a stronger fan would mean higher temps right?
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  1. Best answer
    Well the heatsink is designed for a 120mm fan. You put a bigger diameter fan, did you build ducting so all the additional airflow (outer diameter of fan) flows through the cooler fins?
  2. Thanks for the reply rolli.

    None yet but planning to (any suggestion with the material to be used?). It just feels weird since i have another 140 mm fan (enermax apollish vegas) that would keep my temps the same as the stronger 120 fans with less noise but transferring to the higher cfm yate loon worsens my temps. Im not sure but my initial thoughts of this would be turbulence.
  3. Yes I can agree with the turbulence airflow theory.
  4. Most of the good CFMs are towards the outer part of the fan. So if you switch to a higher CFM, although the other lower CFM kept it the same, it may not have the same CFM.

    In honesty you need to get a heatsink that has matching fans or fans that fit it. Trying to "MacGyver" stuff never works properly.
  5. @rolli
    ill try the shroud first then if it doesnt work then i guess its turbulence. if it does work then the theory of jimmy may be a bit more accurate.


    Hmmm you might be right on the airflow at the edges. I was playing with the fans the other day and it seems that the enermax blows in a more concentrated column compared to the yateloon which has a wider spread. I guess this does confirm one of the threads i read on the 65 fan test on the megahalems. I would still like to try the fan shroud thing but will need to look for a good enough material. (I guess the acts of "MacGyver" ing these stuff is part of the fun of building computers.)

    @rolli and jimmy

    Thanks for your ideas. if you have suggestions on the material to be used for the shroud please tell me. So far ill just test it out with a card and velcro hahahahah.
  6. What material to use depends on how handy you are, thin aluminum or plastic would be my choice.
  7. those would be my choices too but im a bit hesitant with aluminum being conductive and all and plastic dont really know where to get or better yet what to get (plus no tools yet except for my pocket knife and screw drivers and wrenches)
  8. I haven't yet made a fan shroud but i have changed the 140mm fan to another 140mm fan with a more concentrated airflow and it has worked as good as my 120mm fan (140mm with lesser noise). Ill still create a shroud and see if it works hhehehe.
  9. Best answer selected by shoot you.
  10. This topic has been closed by Mousemonkey
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