Can you have too much CFM?

[stymee]

Here's the skinny.

I had the stock YS-Tech 26cfm fans on my Globalwin VOS32 (see sig) and was seeing load temps (Prime95) of around 35°C (ambient of 20°).

I thought one of the YS-Techs was crapping out so I ordered up 2 new Papst 33cfm fans, put 'em on and, HUH?, 45°C? I figured I must have messed something up handling the CPU so I remounted the HSF (with ASII, of course). Still temps in the 43° to 45°. I remounted the HSF like 2 more times, trying a little thinner coat of ASII, a little thicker coat of ASII and couldn't get the temps anywhere near where they were before.

So just for the helluvit I yanked the Papst's and put the YS-Techs back on, and the temps are back at 35°. Hmmmm, the Papst's definately felt (and sounded!) like they were pushing more air than the YS-Techs, and I had them both plugged into the same molex plug (and the Antec 400W psu should be plenty, right?).

Can one have TOO much air? I always thought more is better!

edit: Oh yeah, I'm running at 1.9V in case anyone's wondering.

[Neco]

You did happen to put your papts on the HS upside down or anything did you..

I accidentaly did that with my stock AMD HS/F when I had took it apart, and the difference in temps was noticable.

[stymee]

I should have mentioned that I did make sure they were on the right way (blowing, not sucking), and they were moving some serious air, felt like quite a bit more than the YS-Techs.

[moonunit]

No such thing as too many cfm. :) unless you can't hear yourself think that is.
Maybe it's a turbulence problem, or it's getting trapped in its own heat pocket or something. How are you getting the temperature? It could be the extra wind is not carrying into the socket thermistor.

[francisamf]

I remember reading somewhere that pressure within the case should not be too high, meaning CFM in should not be too much over CFM out. The reason being that if more air comes in, and gets heated due to the HSF, video etc, but less of it is going out, then your ambient will go up. In the end it is less effective. What's your ambient with the Papst fans.

You could try using one Papst and one YS-tech, see if that makes a difference. Compare against keeping the case wide open, etc.

Cheers,
F

[stymee]

I'm getting my temps off the on die thermal sensor, so that souldn't be an issue. I didn't notice any difference in case temps with the Papst's on there, and didn't change any of the other fans.

I'll try one of each and see what happens, I may even try putting them in backwards just for fun.

[tyshy]

hey those temps are really good for air cooling

how much airflow do you have? I get 45C but i have stock HSF and no good compound. I think i found the best fan! A 300cfm Aluminum blade fan that is mainly used for clearing hazardous areas of chemicals and gasses. I almost shredded my hand in the thing.

[Maximus Nickus]

Ouch, having that on your CPU would be awesome!!!!

[francisamf]

Is it at all possible that you're running out of available wattage, and using the new fans results in not enough power going to the heatsink fan?

I'm just thinking out loud here so don't ask me where these ideas come from.

Cheers, and continued luck!
F

[Patchmaster]

I don't know if this really applies in your situation, but on my BP6 I noticed when both fans were blowing in the same direction (either sucking or blowing -- didn't matter which way) they seemed to interfere with each other. It's like there wasn't enough room for the air to escape and the fans just ended up fighting each other. I got better results setting it up so one fan sucked air out of the heatsink and the other blew air into the heastsink. (I've since replaced both heatsink fans with one GIANT fan that moves enough air to overcome any resistance within the heatsink or the other components on the M/B.) You might want to give the push/pull idea a try.