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Fan Ducting to my CPU

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Restorer

Member
Joined
Aug 11, 2003
Location
Los Angeles, CA
Increasing Airflow to Lower Temps

I've overclocked my Athlon XP 2500+ (great overclocking processor by the way) to 2248 MHz. I've had to increase the Vcore, so it's running hotter than before. I currently have a Thermaltake Volcano 11 with the fan grill removed, controlling the fan speed manually. All case fans (2 intake in the front bottom, 1 exhaust blowhole in the top, 1 rear exhaust) are 80mm Vantec Stealth fans. The power supply has three fans. I also have a slot blower 2 slots under the video card. To decrease the CPU temperature, I want to put an intake fan on the left side of the case, ducted to blow on the CPU heatsink. I have a 120mm Stealth fan that I want to use, but it only blows 53 CFM at full power. The Smart Fan II that's on the heatsink now blows 20.5 CFM at its lowest speed and 75.7 CFM at the highest speed, which is where I've had it to keep the CPU at 50C under load. As in the link below, I will add another 80mm case exhaust fan to the rear.

Adding a case fan:
http://www.virtual-hideout.net/articles/pc60_exhaust_mods/index.shtml

My main reason for this mod is because I've noticed that airflow must really be bad in my case. With the side off, I can feel no air flow from front to back when I put my hand over the motherboard. Also, last night my room temp was about 76F and the processor was running at 49.7C. Today my room was somewhere around 86F and the CPU only increased to 50.5C. When I take the side off the case, temperatures drop a few degrees.

My questions are, then: What do you think of my idea for a duct? Will it work? Can I use only the 120mm Stealth fan on the large end of the duct to effectively cool the CPU, or will I have to run another fan on top of the heatsink, in addition to the Stealth?

EDIT: If you are viewing this thread for the first time, there are supposed to be pictures here. They probably will seldom appear. If you're interested in obtaining these pictures, e-mail me and I can host them elsewhere (and change all the [img ] tags to put them back in here).
Also, as with all old posts, ignore my sig in context with my posts; it describes a much newer system.
 
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Okay, stack up a bunch of tornados until they stick out the side of the computer and cut a hole in the side. make sure there are no spaces around the hole when it is on the computer with the tornados sticking through it.

I have no idea how well it would work, but it sure would be a cool test. :D
 
Maybe Something Quieter...

Heh.

If I had a separate room to put my computer in, maybe I would do that. But as I don't (and water cooling would be much more efficient in every respect to that anyway), maybe I should clarify a little. You'll notice that all of my case fans so far are Vantec Stealth's. I want my computer to be livably quiet - something I can listen to music at low volume with. In a month or so I'll have to move this computer into my dorm room, so I'd like it to be as unobtrusively cool as possible. :)

case_airflow.jpg

A diagram of my current airflow situation. It looks like perhaps the cool air from the front intakes is being blocked by the ribbon cables, and then sucked out through the slot cooler. The processor recycles a lot of its warm air as well.

If I can take out the Smart Fan and use only the ducted 120mm Stealth to cool the CPU, I can have noise down to 33db (using the rules of thumb at http://www.customaudiodesigns.co.uk/articles/decibels.htm), not counting vibrations or insulation, while still pushing around 110 CFM total through the case. If I find I have to leave the Smart Fan in to boost cooling during peak usage, the minimum will be a dB higher at low speed and over 48 dB at full speed.

Comments? Suggestions? Please? :)

Oh, I should also mention that I'm not quite sure what my true CPU temperature is. The temperature probe on my Enermax panel says that the bottom of the heatsink (near the CPU core) reaches 50C. The BIOS, however, says 46C. Which should I trust? I have a Gigabyte GA-7VAXP motherboard - I'm not sure if it uses the processor's internal diode to check temperature or not.
 
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You might want to grab and Ac unit or an open window if you overclocking in a tight dorm. !st off you could try rounding your cables for only 89 cents. Grab an E-xacto knife and make a small cut between the wires about every 3-5 wires. Then pull them apart. next use electrical tape and round them. You might want to put zip ties in some places to make sure they are easy to deal with. I would got for a blow hole in the top of and case and another intake fan somewhere.
 
You might want to grab and Ac unit or an open window ..... you could try rounding your cables ...

My university is right on the beach, so no problem with A/C - I'll just have a window open when I'm under load. As for the rounding of the cables, it's something I'm willing to try, but I know the 80-wire cables are harder to split without damaging them. I'll try it with a safety pin, but I'll have to get more electrical tape. :)

I would got for a blow hole in the top of and case and another intake fan somewhere.

I already have a blowhole in the top of my case, as well as a third power supply fan exhausting from the same area. I don't know where I'd put an intake fan (see the front of a Lian Li PC-60; I have two CD bezels and a fan/temp panel), aside from an idea I had with three 40mm fans in a 5.25" bay bezel.
 
You might try this, I was a bit leery about rounding my cables so I wnet to an automotive dealer and purchased 8 feet of .5" and .25" wire tubing. It comes with a slit the whole length and the ribbons and wires fit in nicely.
 
I managed to split my floppy cable and it's temporarily rounded with scotch tape, but the 80-wire IDE cables are much harder. I'm halfway through the first (long) segment of the first cable, using a sharp sewing needle, but I've already exposed the wire in several places. If I end up cutting a wire through on this cable, I think I'll give up and buy pre-rounded cables.

I have some "cold-shrink" electrical tape/insulator around here somewhere; once I find it I'll wrap up my power supply cables and the floppy cable.
 
I rounded my floppy cable and one EIDE cable (those are a pain!) and wrapped bulky parts of my power cables. I redid the routing of all the cables again, and now I think the airflow will be better. I haven't tested it yet, though.

case_cleaned.jpg


I won't be able to obtain a dremel for a little while, so my duct (which I still want opinions on! :D ) will have to wait. If this doesn't drop my load temperature, I have another idea, but it won't be able to work in full until I get my dremel. I'll keep you all posted.
 
WOW:cool: that looks so much better, nice neat cables, you did a good job. I would imagine that will help your airflow problem significantly. Now that you have your cables squared away you need a blue CC and a window to show off what you have in there..

Good luck on the ducting mod. I ve been tossin that idea around in my head as well.
 
Thanks :D

I brought down my speed a bit so I could use the computer without worrying about temperature or stability, and today when I went to bring it back up, I realized: 12 x 183 does not equal 2248. :eek: I have no idea what my actual previous speed settings were. I got it as close as I could, 2250 MHz (12.5 x 180), and I've been Folding to keep it under load.

:mad: Well, I just saw that my PC's frozen up. Perhaps I should run it at a higher Vcore. I was getting lower temperatures, but now I'm not sure what I'll get because I may have been running at +7.5%, not the +5% I'm at now.

Once I test this to make sure it's stable again, I'll be back with the temperatures and an explanation of another cooling idea I had.

UPDATE:
My temperatures are down to 49.3C. Not much of a drop to be of consequence; the ambient temperature will affect it much more. I'll install my next idea and test it thoroughly, then post some pictures of it.
 
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I'll make this one short: my idea wasn't as successful as I had hoped. I wanted to get the air from the intake fans to the upper part of the motherboard, which produces the most heat with the CPU heatsink and the RAM. I attached the 60mm fan from my stock heatsink to the top of the lower HD cage, angled upwards, so as to suck air from the intake fans and direct it toward the upper part of the case.

intfanclose.jpg

(Here the fan is actually backwards - I discovered it after testing a while. I reversed it and tested again.)

intfanfar.jpg


This airflow redirection technique only brought my CPU temperature down to 48.4C; which is not that bad, but it's an advantage easily lost by the normal daytime increase in ambient temperature, and not worth the extra decibel from the 3500 rpm fan. But I do notice that the temperature is more dependent on the outside air, meaning my airflow is better. I guess the only thing I can really do now is to bear the higher temps or drop the clock again until I get my dremel.
 
from what i see, you need zip ties to clean up your clutter. and cable origami

the case def seems to need more intakes. the front ones are probably drawing air through a bezel right? through the weenie crack the bottom and perhaps a lousy grate? you can cut through that all. thats what i did. youd still have the harddrives and the rest of that metal in the way though.. so more fans are needed. add a lot of side intake fans delivering air directly where its needed:)

right now you have two probably heavily impeded intakes, and 3 exhausts. not that cool. more intakes then exhausts is a good thing



case.jpg


my solution was to just slice and dice:) then again its an old ugly case. fans where ever they fit. i've added a 3rd vantec stealth to the side since that pic. 2 are 92mm. air leaks out the cracks and all the vents, heck i saw dust marks on the desk in the shape of the vents, so i know the case is really breathing:)

i just have to duct the cpu next.




taped washable furnace filters over it all:) so ghetto, but with lotsa air comes lots of dust:p air can go through the relatively thick mesh sideways too, so air path is slightly less restricted, plus its held a tiny bit away by fan grills. fugly but it works. i didn't like those chinsy foam ones they sell at comp stores. the plastic holders look like they'd kill air flow, and the filters let too much through. naybe later i'll get some u shaped aluminum or plastic from home depot to hold the filters:p for nicer looking cases, just get premade aluminum mesh to match
GhettoFilteredcase.jpg
 
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the case def seems to need more intakes. the front ones are probably drawing air through a bezel right? through the weenie crack the bottom and perhaps a lousy grate? you can cut through that all. thats what i did. youd still have the harddrives and the rest of that metal in the way though.. so more fans are needed. add a lot of side intake fans delivering air directly where its needed
The front intake fans are sucking through two grates and a filter, but the way it's done on this case is better than most. I'd prefer not to cut through the nice front of my Lian Li. I can and might take out the removable grate/filter, but I want to keep dust out of my computer as much as possible. I'll be moving to the beach, and that beach dust is deadly to electronics.

right now you have two probably heavily impeded intakes, and 3 exhausts. not that cool. more intakes then exhausts is a good thing
I disagree with this. Sure, with positive pressure the dust won't be pulled in through and lodge in the cracks, but there are more important factors. Positive pressure in a case will decrease the effectiveness of each intake fan, and run the exhaust fans faster than they were designed to be run. The higher density of the air will tend to impede airflow within the case. By the way, I DO have a slot cooler which puts out at least 20 CFM.

heck i saw dust marks on the desk in the shape of the vents, so i know the case is really breathing
Now that sounds really bad. If you have dust marks from air coming out of your case, then the air in your case must be filled with dust to begin with. And I don't think your case is breathing - maybe more like leaking or constantly exhaling? :)

My plan is to have five total exhaust fans (including the slot cooler) exhausting around 130 CFM (I can't be sure because of the power supply), and three intake fans bringing in 107 CFM. My average airflow would then be around 118 CFM. I have other ideas for intake, but before I use them I need to get more exhaust.
 
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Now that sounds really bad. If you have dust marks from air coming out of your case, then the air in your case must be filled with dust to begin with. And I don't think your case is breathing - maybe more like leaking or constantly exhaling?


oh, i neglected to mention that the dust marks were before i put on filters:) oops:)gah! and the top fan is exhaust blowhole, obviously.

every fan from both antec psu fans to the cpu fan are connector to the fan speed controller for both cases. so balance and noise control can be tweaked at will.

and i didn't mean massive positive pressure, just slightlly positive. you can't really have massive positive pressure with pc case fans anyways, their ability to figh pressure is lousy. my exhaust fans are higher rpm then the many intakes. its also balanced out by the filter which like all filters, slightly lowers airflow. also have to take into consideration the air path is not straight through which decreases intake efficiency again. case is filled with 1" accoustic foam to boot.

FrontView.jpg
heres the normal looking case:p

IMG_1230.JPG
 
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ok fist thing is to try to move your hard drives away from in front of your fans, you should be able to take them up and get them out of there, next take out the metal cage that holds the hd and any other obstruction to the front fans. then put your case side back on, I know alot of people that think with the side off they will get better airflow. but that is wrong. when you seal up your case by putting the side panel on it you actually create a pattern for the airflow to move. Then all of the exhaust fans will be doing something. you see when they are sitting there open with no side panel they just blow around the air that is by them, not actually giving a a stream of air moving through your case. this will also help to pull airt in the front of the case becouse the exhaust fans will help the front fans get air into the case. nest if you want to really make it nice, try a duct from front of the case on in. also you can alsways put an inlet on your case side with a 90mm fan or so to get air into the case even better. Nice job on the wiring, that was going to be my first sugggestion, but you cleaned it up nicely.
 
move your hard drives away from in front of your fans, you should be able to take them up and get them out of there, next take out the metal cage that holds the hd and any other obstruction to the front fans
I could move one to the bottom of the upper 3.5" bays, and the other to the hard drive adapter built into my Enermax panel in the lower 5.25" bay. I can't move them both to the upper 3.5 cage because I'll be making a rheobus to put there (and the top bay is occupied by a floppy drive). Maybe I should just mount the hard drives vertically on opposite side of the lower cage - will that still block a significant amount of airflow?

then put your case side back on, I know alot of people that think with the side off they will get better airflow. but that is wrong. when you seal up your case by putting the side panel on it you actually create a pattern for the airflow to move. Then all of the exhaust fans will be doing something.
Yup, definitely. With the side panel off, the exhaust fans hardly have a purpose, and it's impossible to estimate the volume of air flowing through your heatsinks, leading to varying cooling results, especially with the CPU cooler.

Time for another progress update!
I put together a duct mock-up last night with my fan, tape, and paper. When I first checked the duct position in the case, I noticed that the paper roll was just too big (in diameter) - it would be constantly recycling heated air from the heatsink. I fixed that by having the front side bent towards the rear of the case. Since I don't have a hole in the case yet, I obviously couldn't test its effectiveness, but I took some nice pictures. :)

mockduct.jpg

mockductplaced.jpg

mockductclearance.jpg


If I can find enough cardboard, I might put together a temporary replacement panel with the fan/duct included.
 
I went out today and bought a cheap Dremel knock-off, some lapping sandpaper, and a 2-liter bottle of soda to cut to size as my duct once I finish off the liquid it contains. :D Any suggestions on household items that are perfectly flat? I don't have a nice piece of flat glass anywhere.
 
Dude, First thing is when you take the side of your case off you totally distrupt the air flow. Of course you won't feel air moving across the board because it is all flying out the open side of your case.

Secondly, clean up your wires. They look better, but you still got a ton of wires going all over the place in there. Tape those USB wires to the botton of the case or something. Get round cables. They are only like $1.50 at SVC. Screw the hassle of making them yourself.

Lastly, Put a big ol fan on the side. I slapped this huge 120mm fan on the side of my case and with a speed controller I can turn it way down for silence when I'm not at load. 120mm fans are so much better because they push just as much air if not more, but are much quieter.

I have 2 120mm intakes, a 120mm exhaust and a 60 or 80mm PSU fan <--can't remember the PSU fan.

I have found depending on the ratio of CFMs to many intakes does reduce their effiency because of high case pressure, to offset this I've opened up a few empty PCI slots.

I like positive case pressure though because it keeps the dust down a bit. Hope this helps, checkout my rig below. Even with my wires like this I still think it's messy. I need to wrap them in wire looms or something.

EDIT: Oh notice how I have them all twist tied up at the top. You should try and do this as much as possible or tie them to the rails. The worst is having them dangling around inside your case. Remove as much slack as possible. Good Luck ;) :) :p
fb609fea.jpg

fb609fd0.jpg

fb609fe6.jpg


This picture serves no purpose but I like it :)
fb609fcb.jpg
 
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