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Case air flow dilemma

Last response: in Overclocking
April 13, 2001 5:05:03 AM

I have been doing a lot of testing and I have figured out that without my case side on, my cpu temp is about 6-8 deg C cooler than with the sides. Once the side is off it doesnt even matter that I put a huge box fan blowing into it, it will never drop below 38C. Then I left the sides off and placed the open side next to my desk which is its normal spot. The idle temp increased by 3 deg to 41C.
So it seems I have a problem with air flow in my case. I already have one fan in front with a vent in one of the bays and i have a dual exhaust fan in a pci slot. I was thinking of getting two (2) big 120mm fans to put in the side of the case, one blowing in one sucking out. Im not worried about noise, I already have a pretty loud FOP 32. So do you guys think this will work or is there a easier alternative?

Even a broken watch is right twice a day...

More about : case air flow dilemma

April 13, 2001 1:25:44 PM

I have a 1.2/266 Tbird on Asus A7M266, Geforce2 Ultra with(original, not very good heatsink fan (HSF)), Silverado HSF on cpu, 1 80mm fan in power supply, and 2 * 80mm Papst fans in case, 1 at front sucking air in, and the other at rear exhausting air. I have noticed the same thing: with one side of case removed cpu temp is 38C when system is lightly loaded, with same load and case side on the temp goes up to
43C. Your idea sounds to make sense to me. I was considering doing similar to my system. Also I've read 120mm fans move more air and are quieter, due to having larger diameter blades that turn slower. Let us know how you get on. P.S you could try replacing wide IDE disk cables with round profile ones, that might impede air flow through your case slightly less. Every little thing helps.
April 13, 2001 3:00:59 PM

I was gonna get the rounded IDE cable, hehe funny you said it. The only tough thing is finding a place that can keep them in stock. Ill let you all know, and since this is my first adventure in case modding Ill probably be posting here a few more times before Im through.

Even a broken watch is right twice a day...
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a b K Overclocking
April 13, 2001 5:49:55 PM

have you ever thought of rounding them your self, no knife needed just zipties, or electrical tape (colored looked cool) mine are orange with neon green zips for affects

The squirl is out!
April 13, 2001 10:38:49 PM

You don't have to run those fans at full 12V if you don't want to. You can run them at 5V, 7V, or rheostat them. You can also get an AC fan, and rheostat them down to 25V or so, and it's right next to silent while still pulling a bit-o-air.

You can round your cables yourself too. Zip ties work well, just don't crank the UHHHH! out of them, and it won't interfere with signaling.
a b K Overclocking
April 13, 2001 10:47:10 PM

Remember that hot air rises, there fore any exhaust fans you put in your computer would do a better job near the top of the case, and all intake fans should be at the bottom. One thing you might want to check on is the amount of air that is coming in through the front intake fan. I had to drill some extra holes in my case to improve the airflow. Another thing you could do if you really wanted to get in the heavy of it, is put a big 120mm fan at the top of the computer. (You would of course have to cut an exhaust hole in the case) A major factor is the clutter in the case, move all the extra wires and crap out of the way of the airflow. Also you could check out and get one of the card coolers, they do a great job at lowering the whole case temp.


Those who do not know, speak. Those who are silent, know.
April 15, 2001 3:08:49 AM

well i used electical tape to roll up my ribbons as much as possible, but it hasnt made that much difference. Im kinda reluctant to get the big fans because the open case is workin so well. I have a compressor to blow it our so im not that concerned about dust.

Even a broken watch is right twice a day...
April 16, 2001 3:00:19 PM

Hot air rises - but a serious case shouldn't give it a chance. If natural convection is a major force in your case, then you ain't pumping air fast enough! :o )

I would have thought air should be pulled in the front and up over the cpu, and then out the rear a the cpu exhaust rather than drifting up to the top of the case...

-* This Space For Rent *-
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April 16, 2001 4:14:24 PM

Yea - had hi case temp in a coule of cheap mid-tower boxes!
Fixed the problem with those cheap little drive cooler units - the plastic inserts with 2 small fans that go into the front of full sized bays.

Turn the fans around so they blow out(exhast) and put it into the very top full sized drive bay...
(may have to move everything down in the full sized bays so the top full sized is empty)

WOW - droped my case temp(and all temps)signifigantly!
(from about 112-115F to 98-100F)
A quick, cheap, effective fix if ya have an open full sized bay!
a b K Overclocking
April 16, 2001 11:45:13 PM

Obviously in the best case scenario the cool air would come in from the front case fan, and move quickly up and past the processor to be ejected my the rear fan and/or the power supply fan, but it seems that this is not the best case here, and if his case is small there might be pockets of hot air, just chillin' (sorry about that one) in the case


Those who do not know, speak. Those who are silent, know.
April 17, 2001 1:23:34 AM

actually intake fans are not necessary. in fact they increase the temp. just put in the exhaust fans and the pressure difference will pull the air in

Bill Gates? Never heard of him! :cool:
April 17, 2001 1:35:08 AM

<<actually intake fans are not necessary. in fact they increase the temp. just put in the exhaust fans and the pressure difference will pull the air in>>

Well, that's a new one - 'almost' every case person I've read from does it this way.

I cannot see how blowing air into a case increases temperature, unless you are doing it at 40psi and expecting the pressurisation effect to heat the air?

Drawing air into a case by exhaust is not at effective as trying to push air in. Generally it requires much more effort to get the air into the case. Therefore you may have 2 or 3 fans blowing in to create the required pressure increase.

-* This Space For Rent *-
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April 17, 2001 3:08:08 AM

Ok that staement about intake not nessesary and that it actually increases temp is absolutely bogus. Where the hell did you hear that, or did you make it up?

- Tempus fugit donec vestrum relictus tripudium. Autem amor praeterea magis pretium.
April 17, 2001 3:47:19 AM

If you sealed the hell out of the case with duct tape, and silicone, you're right. That would work, although it's not terribly efficient. As a matter of fluid dynamics, it's <font color=red> always</font color=red> more efficient to push rather than pull a fluid. Either way, you'd want the majority of your intake air from the bottom side of the largest volume of ambient air.

Along that line, you're better off pumping 140cfm into your case, then opening 'blow-holes' to vent the air. Exhaust fans aren't really meant to add any extra cfm to your case. Instead, they help shape the airflow through the case so you don't have any static pockets.
April 17, 2001 5:38:12 AM

Actually Im talking about CPU temperatures and NOT motherboard temps. Right now with my case off, I have 36-38C idle temps. With the case on, I get 44-46C idle temps for CPU. My motherboard temps are always between 26-28 no matter if the case if off or on. SO there obviously isnt enough air flowing across the cpu because i think my PSU fan is blowing in and not sucking out. My case if a full tower with one 80mm fan intake int eh front, a PCI slot dual exhaust fan and a open bay at the top. Come to think of it, my so called exhaust may just be pulling all the air from the fron of my case right back out the back as soon as it gets in. Ill keep doing expirements and report back.

Even a broken watch is right twice a day...