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When installing fans, should the ones with more CFM go in front or back?

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Mav

Registered
Joined
Jun 21, 2001
Should the bigger fan(s) be used for intake or exhaust?

really what im asking is- does the PS exhaust air out of the case, or just for itself?

and...will about 100CFM of airflow be sufficient for a tbird (1.0 or 1.2) OCed to 1.4+, Enlight 7327 case, sound card, dvd, floppy, network, mobo, and HD?

-eric
 

Phil

Senior Member
Joined
Jan 13, 2001
Location
Bolton, UK
oh god this is going to set everyone off.
It is best to aim for a well balanced flow for both intake and exhaust.
I tend to go for a slight posative pressure, i.e. more intake as if you have negative pressure more dust is sucked in.
But this is really only an opinion as you will surely see people saying "more exhaust as they will make up for the lack of intake by sucking through all the gaps in the case" well this is where the dust comes from, and it isn't much air not enough and not at enough pressure to actually cool anything.
 

samuknow

Member
Joined
Feb 19, 2001
Location
Indianapolis, IN
I agree Phil, I have a slight pos pressure and my case temps are just a few degrees above ambient. But truthfully, it is best to try both ways out and see which works best for your app. Make sure you clean up the flow through the case. If you can remove the sheet metal (holes) where the fans are going to be mounted. This will net you better flow and less noise.

Goo luck
 

ManOfKnight

Member
Joined
Jan 26, 2001
Location
Back in Iowa :( Come on Gators, Get up and Go!
i personally like more air going INTO the case...as my house is cooler than my inside of case, it sucks more cool air into and around my HSF and components...the exhaust i don't agree with having more...because if you are blowing out more, then where is any cooler air going to come from??? the cpu and HSF is not getting any cooler without cooler air coming in...
but that is just MY opinion
 

Flash

Member
Joined
May 21, 2001
Well, let's be clear that, unless your case is completely sealed, the pressure inside *will* be equal to the outside pressure. Nature abhors a vacuum and all that. It's just a question of, do you want the the vast majority of the outside air coming in through your intake fan (which should be filtered), or do you want a bunch coming in through your drives, empty slots, screw holes, etc (which are not filtered). I think the answer is self-evident.
 

Phil

Senior Member
Joined
Jan 13, 2001
Location
Bolton, UK
Also you don't need to have much in the way of airflow. I have about 77cfm in and 60cfm out, my case ambient is technically 3-4oC below room temp because I keep the pc on the floor which is that much below room temp at my desk hight. My motherboard is 3-4oC above that which I can't get any lower with more/stronger fans or with the case off. And the cpu temp is about 12oC above case air ambient which I'm working on knocking about 5oC off at the moment.

Update: Just noticed what you said about the psu, depends really, if it's a dual fan setup then it will definately act as an exhaust, if it's single fan then it will still act as an exhaust as it has to get the air from somewhere but not as effectively as a real exhaust or with a dual fan setup.
 

Beggar

Registered
Joined
Jun 23, 2001
this is kinda on the same topic, you know those brushless fans we all like using so much, is it just me or have u humans found that putting 2 or more in series if u like, doesnt double airflow at all and infact tends to stop it unlike a normal motorised fan?
This leads me to beleive that the RPM of these things is electronically preset, so even if there is an extra force pushing on them, they will not turn any quicker, therefore air should be still before each fan for optimal airflow and fan chains should be calculated on this.

Or is this just the case with the cheapy $3 ish fans i use?