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Is 104cfm in and 79cfm out enough?

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AllGore

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Joined
Oct 26, 2002
Location
England
I am having a little problem with airflow at the moment, the case im using isnt the largest and when i get all the fans in there wont be enough room for any more except a PCI blower. Here is an image of what i want it to look like (please excuse paint, i dont have too much time on my hands at the moment)
case1.gif


as you can see its er... stuffed, I have no room for more exaust fans unless u have any ideas... I was thinking about a PCI blower but i dont think it can push enough cfm's. The only fan im willing to change is the psu exaust and 120mm intake.
 

TLKfatman

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Joined
Sep 2, 2002
Location
Concord NC
i would have to say u would want 200 cfm coming in the front and about 100 going out

u can alwas get the psu with the fan that sucks hot air from cpu hs and out works good

can alwas put in a blow hole

?are u planing to oc
?what hs u gunna put on that
?what vid card

and welcome to the forum
 
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AllGore

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Oct 26, 2002
Location
England
1. thanks
2. yes i am planning to oc
3. by saying hs u mean the one on my processor? if so its a volcano 7+
4. the vid card is a Asus V8420 geforce4 ti4200 128mb.

the numbers you are saying... 200 in 100 out seem to be quite far apart, i was thinking that u want positive pressure, but having too much going in would just make the hot air build up. 200cfm sounds like 3 120mm fans... i just dont have room for them in the case i have. To add more cfm in, could i add another 80mm intake next to the other two? i DONT want it sounding like a hovercraft. All the fans im suggesting will have blowholes with the metal all cut away, including the on-case hingerguards.
 

WarriorII

Moderator #666
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Nov 13, 2001
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Moderating
For an exaust, if you have no more room inside your case, On the back pannel of the PC box, where the exhaust "should go" cut the grill out of the case and mount the fan on the outside of the case over the hole. Just use a fan guard.
 
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AllGore

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Oct 26, 2002
Location
England
wow!! 130cfm!! that'll be heaven :D
i think i can have 2, one at the top replacing the 80mm and the other at the bottom, i can put them on a bus of some kind to stop it being too loud if i want to watch dvd's or whatever. Thanx for the help. I think my question is now answered. I dont think they sell to the uk but im sure some site will have simular ones.
 

Lithan

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Oct 24, 2002
Location
PA
I've got a 102cfm fan in and whatever fan comes with an l&c 300atx out (20something cfm I'd guess) It's in a steel case with no additional fans except the Cpu, Video, and chipset, and I'm 2.4 degrees celsius above ambient at just above idle... Get maybe as high as 5 above ambient at full load. This is using mobo sensor, which read into the upper 30's when I had just the PS fan, (low to high 20's depending on ambient now.) Not perfect measurement, but seems to work fine. Oh and in case you didnt notice that is alot more intake than output (there are a few slits on the back of the case just above the pci slots, and air is streaming out of them.) I'd imagine it's destroying my Power supply fan... but it's definately cool. Yes, negative pressure gives a slight decrease in temps over positive pressure generating the same flow... but in most cases it should be such a minute differance that it is nowhere near worth the trouble of dealing with the dust. (And sealing all the vent holes is just plain stupid unless you have ~= input and output.) Just my 2 cents of course. I'd stick with what you've got... What case temps are you getting?
 
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AllGore

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Oct 26, 2002
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England
I think you must remember that im just asking for ideas, i havent bought any fans at the moment except one 80mm intake at the front, its something like 30cfm but im not 100% sure, i mainly got it to show my parents i was serious about modding my case and they like the looks and told me to buy a window...heh. Ok well back to the question
51 CPU*
32 MOBO

*Remember my volcano fan is at minimum speed cos im not playing loud music.

When i add the fans there will be a balance so im gonna put a bus on when i dont need the extra cfm.
 

Deathknight

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Sep 8, 2002
Location
Chicago
AllGore said:
the numbers you are saying... 200 in 100 out seem to be quite far apart, i was thinking that u want positive pressure, but having too much going in would just make the hot air build up.

Your case isn't going to become pressurized and explode, the air is gunna get out hehe:D

I think the idea of having more intake than exhaust is that having X amount of exhaust is going to pull that amount of air into the case. If your intake fans are not pulling that much in its gunna come in 1 way or another (various crevices and air holes etc). To combat dust you really want the air coming through your intakes which have filters on them. Anyways thats the opinion of the people who prefer intake over exhaust I think.
 

markshelby

Registered
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Apr 19, 2002
That's a lot of Cooling

Positive and negative pressure by themselves affecting temps is probably a myth IMO. Plenty of million-dollar computers with huge heat generation have been designed with exhaust fans only over the past 30 years or so, and plenty of others the other way. The most important thing is to have good circulation and turbulence.

Good circulation means getting the hot air out of the case, i.e. making sure no part of your case has dead spots of hot air that don't exhaust. Sometimes adding fans helps, sometimes moving cables helps, sometimes putting a cardboard duct over the cpu heatsink to an exhaust fan can work wonders.

Good turbulence means increasing the rate of heat transfer from the hardware to the air. If you put your hands over an exhaust fan port and the air coming out isn't that much warmer than ambient, your next fan should be an internal fan that blows down right on the graphics card and northbridge etc.

Hope this helps.
 
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AllGore

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Oct 26, 2002
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England
When I wrote that the hot air will build up I meant that the air that is entering will stay in longer and heat up the air being blown in before leving, not build and explode. Im making sure the only large openings have fans in and the rest are small and evenly spread through the case.
 
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AllGore

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Oct 26, 2002
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England
i wasnt sure how much i would need, TLK suggested 200cfm in and 100cfm out. I was thinking less in but simular out. I now found that if i want extra cooling i could get those 120mm high cfm beauties to start up incase i mite need more cooling. I dont think i need it all but it will look really good so im doing that.
 

Lithan

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Oct 24, 2002
Location
PA
Hey james Miller I just realized something.. Is there a fan in the power supply of your fanless system 2?
 
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AllGore

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Oct 26, 2002
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England
heh... mine was too hot to touch last evening when i went to turn it off. My mobo has this REALLY bright led on and the only way to take it off is to pull out the lead and its hot behind there
 

james.miller

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Jun 8, 2002
Location
Dunstable, uk
Lithan said:
Hey james Miller I just realized something.. Is there a fan in the power supply of your fanless system 2?

nope. no fan:D

AllGore said:
i wasnt sure how much i would need, TLK suggested 200cfm in and 100cfm out. I was thinking less in but simular out. I now found that if i want extra cooling i could get those 120mm high cfm beauties to start up incase i mite need more cooling. I dont think i need it all but it will look really good so im doing that.

well just to let you know, if you dont count my psu fan on my athlon system, i have 0 cfm in and 0 cfm out