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Considering Ducting (mostly out of boredom)


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Ok so my first overclock is successful and stable. Its pretty mild, im running 2500mhz @ 250mhz fsb x10. I live up in Washington so it doesn't get too hot in my room, maybe around 75F max on a hot day, and obviously a lot cooler on a cool day. Anywho, I usually idle anywhere from 39-41C and does not exceed about 48C under load (the only time where it gets above 50 is running Prime95 on each core, which makes me really nervous).

 

I'm using the stock AMD heatsink and fan and because of the setup of my case I was wondering if I would be able to benefit from ducting and if so what configuration would work best for me. At the present, I feel that I have an unbalanced intake/exhaust ratio. The front of the my case is all like wire mesh with filters.

Intake fans:

1x120mm fan on the front

 

Exhaust fans:

1x120mm fan in the back

1x80mm fan in the upper back

1x80mm fan in the top vent

and of course the fans in the upper back from my PSU

 

I'm thinking this can't be terribly efficient since theres more exhaust than intake. I was thinking that I could flip the 80mm in the upper back around in its mount so that its sucking in air and then use one of those cpu ducts that a lot of the modding sites are selling and i guess an adapter (i think standard HSFs on AMDS are 60mm but I'm not sure). So basically this is a 2 fan system. The reason why I wouldn't get rid of the fan on the heatsink is that it is useful because it throttles according to my cpu temp (spins up to 100% at 44C), whereas the 80mm case fan that would be sucking in air from outside the case is a dumb fan that only has 1 speed. Plus, the air is going all in 1 direction, towards the heatsink fins, so I figure 2 fans pushing/pulling air in 1 direction would help compensate for the resistence of the sides of the ducting and all that.

 

I drew up a real quick diagram to show what I'm talking about. Please note the metal cage by the 80mm intake fan wont be there, i have removed it from my case.

ductingdrawing1fr.jpg

 

So basically, cool air from the back of the case (which conveniently is where the window in my room is located) gets sucked through the 80mm fan, throught the ducting right to the stock AMD fan which blows it over the heatsink fins out into the case. This will hopefully even out my intake/exhaust ratio and perhaps provide a direct pipe of outside air to my cpu.

 

Here are my questions: Is this the right way to go about doing this? I've seen some people that only use 1 fan in their ducting, where it just sucks in air from outside and pushes it towards the heatsink. This seems inefficient to me because the 1 fan has to push the air all the way through the ducting onto the fins. Wouldn't 2 fans be more efficient? Secondly, would I be needing an adapter of some sort if this is the right way to go about doing this (i think the stock HSF for amd is 60mm)?

 

Oh and lastly, anyone know of any websites that sell some good looking ducting if this turns out to be a good idea to knock down my cpu temps a degree or two? I don't really want my case looking like the back of a dryer, so would prefer some style :D

 

Sorry to be so verbose, I just want to provide all the pertinent information in the first post. Any and all help is appreciated.

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Pull air in low where it is cooler, have your exhaust exit as high as possible on your case. Don't try to fight physics. However, pushing good CFM thru your case is still more important.

 

Also, I've read that negative air pressure inside your case is good, as long as you have a place where fresh air can come in.

 

I think your setup is fine. I have 4 exhaust fans (including PSU, video car, 80mm, and a 120mm). Try lighting a match and shaking it out right in front of a vent. If the smoke goes in, you've got good airflow.

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I would take in air in the ducting low if I could but the way the armor is set up it just isn't plausible. The intake fans mount in these things called i-cages. The only size i can put in as far as intake is 120mm. Something tells me 120mm intake -> 60mm cpu fan wouldn't work out right and would look silly.

 

However, there are a lot of holes in the floor of my case (I guess for water cooling) that might be able to fit an 80mm fan. So maybe if I removed the 80mm fan from the upper back and put it in the floor of the case it would be sucking in cool air. The only problem with that is that I would have to route the ducting downwards, so I guess it would have to go over the side of my video card. I guess that would be okay.

 

If I did this mod, I should still have maybe slightly negative air pressure in the case (1x120mm and 1x80mm intake and exhaust but with extra exhaust from my psu).

 

I'm fresh out of matches but I just lit a stick on incense and it got sucked in not only where the front fan is but everywhere on the front panel because its all wire mesh.

 

What say you of my idea for putting the intake fan on the bottom of the case? I'm not sure what size screws the holes are for but they form a sort of grid on the bottom of the case. My concern with air flow right now is that my setup has some jumbled wires near the intake fans and I was just wondering if my cooler would benefit from a direct source of fresh air. I also assume that air flow would be stronger than it is now because there would be an 80mm intake fan and then the 60mm (i think) HSF all pushing air on the heatsink.

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Sorry, didn't realize you wanted to duct fresh air straight to your CPU. I'm not sure exactly how that would work. You would have to reverse the flow of your CPU fan.

 

If you had a side vent where you could hook up an 80mm fan, it would be fairly easy at least to duct the CPU hot air straight out the side in a push-pull config. i.e. CPU fan pushes into the duct, while the 80mm pulls. Some old school info here:

 

http://www.overclockers.com/tips586/

 

I think a good CPU HSF will do a much better job overall, just might be a bit more expensive.

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get the old dreml out and cut a fan hole in your side panel over the cpu and with a fan direct fresh air straight to the cpu then cut out all the grills in the case strech stocking over the fans this makes a great filter and a lot less restrictive improves air flow noend

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I actually dont think I would have to reverse my cpu's fan. I'm pretty certain that the stock AMD heatsink/fans push air towards the cpu. I have mine installed in accordance with the installation guide (the AMD hologram facing outwards) and just by feel it feels like the fan is blowing on the fins. My configuration would be 1 80mm fan on the inside floor of the case sucking into the case, and that air would be piped to the HSF which would be sucking also and then it would blow that air over the heatsink which would then go out into the case. I think that way I would be taking of my system's slightly stronger exhaust fans which would carry the warm air out of the case.

 

I am not planning on getting a new cpu cooler because this way would be cheaper and perhaps even make my case a little quieter. Presumably the only thing I'd have to buy would be the duct, which is just a couple bucks (and maybe some fan screws since I don't seem to have ANY screws in my big-bag-o-screws that fit case fans).

 

If anyone knows about the stock coolers on AMD processors and knows if I'm wrong and if they are actually sucking hot air off the heatsink fins, please let me know, but I'm fairly sure its blowing air onto them. Also, anyone who has tried ducting, your help will be greatly appreciated to see if my plan is the right way to go about this or not.

 

I was just thinking that if I do end up doing this I had better not ever run my case on the floor with long carpet :nod: Shouldn't ever be an issue though.

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get the old dreml out and cut a fan hole in your side panel over the cpu and with a fan direct fresh air straight to the cpu then cut out all the grills in the case strech stocking over the fans this makes a great filter and a lot less restrictive improves air flow noend

My case is windowed so I don't think the cutting thing will work as there is plastic window right over where my cpu is.

 

I also realized that the floor of my case really doesn't have enough holes in it to foster effective air flow were i to mount this new intake fan on the bottom so I'm back to my origional idea in the pictrue above. Air would be sucked in from the upper back of my case and would be piped directly to my stock heatsink/fan.

 

I'm also not too concerned about the grills in the front of my case being too restrictive. They cover a lot of surface area, are pretty pourus and have gaps between them. I don't think my fans are really straining to get air in that regard.

 

I think the biggest detriment to my air flow to my cpu is that the fatass ATX power cable from my PSU really has no other choice but to block the right side of my CPU heatsink/fan. My case has my PSU turn on its side so really theres nowhee else for that big cable to go. If I were to pipe in fresh outside air from the upper back to the cpu like in my picture, this would presumably fix that problem. I'd like to know from anyone who has had success with ducting if my 2 fan ducting idea is any good.

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You want to establish a positive pressure in the case. By that I mean, you want more air coming in than going out. Why? A couple of reasons:

 

1.) The more cool air you push into you're PC, the more hot air that has to come out. (To a point.) If you take the time to plan out the air velocity route, you can maximize the air flow in and out of your PC.

 

2.) Most people want a clean PC case interior. If you have positive pressure (and filters on the intake fans) then dust simply cannot get inside your PC. If you develop a negative pressure in your PC case, you suck in dust from all around the case. Every hole becomes an intake area. Unless you plan on wrapping your case with panty hose to keep the dust down, go for positive pressure.

 

Your case is similar to mine. I have a 120 mm intake (filtered) up front with a 120 mm exhaust out back, along with a 120 mm fan in my PSU. Thankfully, my psu fan is temperature driven so it doesn't run very often. I have my front fan on max and I throttle my rear fan based on noise/temps. I really need to add a second or third intake fan to my rig... I may add it to the floor of my case facing up towards my video card to help cooling there, and exhaust the heat out the back of my rig. But I digress...

 

If you want a good company to buy some cooling stuff from, check out Angry's Sticky

 

At the bottom is a link to a company called SVC. They have all kinds of cooling stuff, and at damn good prices. I went there for a $8.95 fan and spent well over $60 on stuff. Fact is, I saved a lot of money over my favorite on-line retailer... and I didn't even use the 5% discount coupon!

 

You are correct about the AMD HSF air flow. It blows down on the HS. From the looks of things, it's a 70 mm fan. If you have some old 80 mm fans lying around, you can cut the 'guts' out of them and use the outer frame as ducting. Just screw the frames together to make a straight duct, or find a hose that will install into that frame and bend to where you want the airflow. A fan that blows into your stock AMD fan would help quite a bit I would think.

 

I'm rambling... anyway, I hope I gave you some good ideas and was of some help to you. Best regards.

 

Mark

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Thanks for the ideas. Yeah I'm probably going to just buy some ducting. Its really cheap and some people have had some success with it. Plus right now my case (presumably) has a lot of negative pressure since the exhaust fans outnumber the intake fan 4 to 1. Might as well flip around one of the 80s and use it for getting air directly to the cpu. My only concern is that the 80 fan will be located right by the PSU exhaust, so its probably not going to be getting the coldest air possible, but the air exiting the psu isn't really that hot and seems to cool down pretty quickly, so it shouldn't really be a problem.

 

Also I did spend some time today cleaning up the cables in my case. Its looking pretty snazzy. I only had 1 cable tie and then I had some colored velcro ties that do the job but look silly. I'm probably just going to get one of the generic ducting kits (they claim to fit 80, 70 and 60mm fans so I should be good), some cable ties and fan screws. If it does end up cooling down my cpu a little bit, thats a hella cheap alternative to a new HSF :D

 

Fresh air has to be better than what I have now. I opened up my side panel and put my hand in some of the parts of the case and I realized that since my 1x120mm intake fan is located on my hard drive cage, my cpu is getting warm air from my hard drives. Fresh air from the back has got to be cooler than that!

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all that thinking and work for only the price a after market good cpu cooler. my house is 86 right now my case temps are at 38c and my cpu is at 26c for 32 bucks there are good cpu coolers that are the same size as your stock cooler

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You want to establish a positive pressure in the case. By that I mean, you want more air coming in than going out. Why? A couple of reasons:

 

1.) The more cool air you push into you're PC, the more hot air that has to come out. (To a point.) If you take the time to plan out the air velocity route, you can maximize the air flow in and out of your PC.

 

2.) Most people want a clean PC case interior. If you have positive pressure (and filters on the intake fans) then dust simply cannot get inside your PC. If you develop a negative pressure in your PC case, you suck in dust from all around the case. Every hole becomes an intake area. Unless you plan on wrapping your case with panty hose to keep the dust down, go for positive pressure.

 

You should have just called me an idiot.

 

Good points, well spoken. My air management goes back to the drawing board tomorrow.

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Yes but compare that to about 8 bucks for ducting. Another factor in this is that I'm going to try to avoid encouraging myself to push my CPU too far. If I can achieve this mild overclock and keep the temperatures in healthy range (which they are right now, but hopefully the duct will bring it down a little more), I'm happy and wont want to pursue it any further. I'm also trying to avoid the pain in the arse of putting in a new cpu cooler. I'm sure I could do it but thats just not a hassle I could justify right now. With the duct, its like 8 bucks, I route it and put in 4 screws and I'm done. If it doesn't work too well, who cares? Obvioiusly I hope it will and logically I think it should work, but if it doesn't, no big deal, my temps are fine.

 

It really isn't THAT much thinking for me, I just research the hell out of everything before I buy it. Its 1 part good shopping practice and possibly 1 part OCD ;)

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