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Fan air flow question

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October 31, 2011 1:28:25 AM

Hi I am having a problem figuring out which way I should position my cpu fan. I have 5 case fans. Intake: 1 front and 2 side. Exhaust: Top and back. I plan on adding one more top as exhaust and one more side as intake in the future. My cpu fan is the corsair a70. I have it sucking in air from the right and blowing out air towards the back exhaust fan. Is this a good setup? See the pics below for more info. The crude drawings are a representation of airflow. Green is the cpu fan. Blue is case fans. Orange is case fans to be added eventually. Thanks for your help :) 
P.S. I'm not sure if my cpu fan can be positioned up and down cause it might get in the way of the gpu





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a b B Homebuilt system
a b à CPUs
October 31, 2011 1:55:51 AM

You can have too many fans - especially side fans which can disrupt smooth airflow thru the case. Front in, back and top out are the normal airflow pattern. You will need to actually test and monitor if the use of side fans improve or hurt CPU/GPU cooling. Your current CPU HSF orientation is preferred.
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October 31, 2011 2:06:30 AM

Oh okay thank god haha. I had it backwards before and was like something must be wrong. Anyways yeah I have always though the side ones might disrupt air flow. If so I might just leave it how it is or maybe add the top. I'm not too great on monitoring things so I don't wanna go overboard or do something that hasn't been tested. But another things I was thinking was top and front in and back and side out. But that isn't very linear so idk about that one.
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a b B Homebuilt system
a b à CPUs
October 31, 2011 2:17:16 AM

I agree with beenthere. Too many fans can disrupt airflow but really the only way to be certain what is the best configuration for your PC is to test out some different things and see what gives the most ideal temps.
For me, since I choose to OC my CPU, the best config is the one that gets me the best CPU temps. In some cases, a CPU pointed toward the blowhole up top is ideal. In my Antec 900, I found an advantage in the rear exhaust configuration. With one cooler, the side fan wasn't especially beneficial, with my Spre thermax the side fan helps but doesn't fit well so I had to remove it.

Adding a second blowhole on the phantom may look cool, but you are taking the fresh intake air from the front and moving it out the top of the case before it reaches the CPU. At least that is how i imagine the airflow would go, in practice I may be completely wrong. Its possible the CPU fans with a higher CFM rating may grab that air and direct it through the heatsink.

Try several configs before settling on something that may not benefit your system. Remember that airflow is sometimes counter-intuitive and it doesn't care how YOU think it should travel. :pt1cable: 

Positive pressure means more CFMs on intake than exhaust. Negative pressure means more exhaust CFMs than intake. Either one is better than matching airflow on both ends, which is what I mean about counter intuitive. Equal pressure results in pockets of dead air, where heat can build in regions such as the CPU or GPU areas.

The main purpose for side intake is merely to provide fresh, cool air for your graphics card(s). Too much side air flow can be disruptive to overall case air flow.
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a b B Homebuilt system
a b à CPUs
October 31, 2011 2:20:28 AM

BTW, nice looking build!
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October 31, 2011 2:25:45 AM

buzznut said:
BTW, nice looking build!

Thank you! I tried pretty hard on cable management haha. Okay, hopefully I can figure out this airflow stuff. What might end up happening is I'll be too hooked playing games to deal with airflow and my hardware :na:  I'll see what temps I get with what I got right now. What are the ideal temps for cpu and mobo and all that? And what program would I easily see the idle and stress temps? Like I know I have to run prime95 and intel burner and cpu-z after attempting to overclock (god help me not fail) but I am not even sure what they do.
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a b B Homebuilt system
a b à CPUs
October 31, 2011 2:35:05 AM

zachcuden said:
Thank you! I tried pretty hard on cable management haha. Okay, hopefully I can figure out this airflow stuff. What might end up happening is I'll be too hooked playing games to deal with airflow and my hardware :na:  I'll see what temps I get with what I got right now. What are the ideal temps for cpu and mobo and all that? And what program would I easily see the idle and stress temps? Like I know I have to run prime95 and intel burner and cpu-z after attempting to overclock (god help me not fail) but I am not even sure what they do.


Ideal temps depend on your hardware and what you're trying to achieve. Is overclocking part of the goals? Just having an efficient and quiet system? Benchmark busting??

If AMD then I highly recommend using AMD overdrive. I like speedfan as I can see in real time the fan speed. Others prefer core temp. All windows based monitoring software is limited and they have their shortcomings. BIOS temps are more accurate in my experience.
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October 31, 2011 3:27:09 AM

buzznut said:
Ideal temps depend on your hardware and what you're trying to achieve. Is overclocking part of the goals? Just having an efficient and quiet system? Benchmark busting??

If AMD then I highly recommend using AMD overdrive. I like speedfan as I can see in real time the fan speed. Others prefer core temp. All windows based monitoring software is limited and they have their shortcomings. BIOS temps are more accurate in my experience.

I got a 2500k. Plannimg to go 4.5ghz at 1.3v right away and leaving it at that. Not even seeing if I can lower the volts unless I have a prime95 or temp issue. Umm im trying to get safe and stable gaming performance. I dont care too much about benchmarks. Just that I can max out Skyrim and maybe crysis 2 with a texture pack and bf3 at 1920x1080. The additional side fan goes right over the gpu and mobo and I was thinking about sli in the future thats why I thougt that fan might be neceasary. I dont mind some noise coming from my computer.
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Best solution

a b B Homebuilt system
a b à CPUs
October 31, 2011 3:59:55 AM

BF3 max? you'd be looking at two high end video cards for that..Which would require significant cooling. Which makes me wonder what your graphics setup is.

But lets ignore that for now. It looks like the (one) side fan is a good idea. Multiple side fans not so much. The main blowhole and rear exhaust should definitely stay.

Before doing anything else, make sure you have a monitoring program you can work with. CPU-z is a good one, so is speedfan or coretemp. Most Intel users enjoy coretemp.
Regardless of your joy for monitoring, you WILL have to monitor temps if overclocking and especially if overclocking to the level you're talking about. It looks like you've got a decent cooler.

Nice thing is you've got a fan controller for your case fans. This will help in case thermals become an issue.
Next I would take your current config and note the big numbers, that is CPU temp if given, core temps( more important to me), system temp, and maybe GPU. All those can be viewed in Speedfan. Also notable is v core, and any other relevant voltages.

If it isn't too much of a bother, I'd move the A70 into the top exhaust position and note the temps. If it drops any, keep it there. If you don't care because its too much hassle, then forget about it-its likely to be a difference of about 3C max. That can mean alot though for max overclock...

Then you can begin adding fans to see if there are any benefits to doing so. With the Phantom you currently have 1 120mm in front and one in rear exhaust, yes? and a 200mm blowhole and a 200mm side panel intake. You also have two side intakes blowing directly on your hard drive cages. That's a lot of side intake, but what it does do for you is create a positive pressure system which is good.

By adding another 200mm top fan, you'll be bringing the system closer to a 0 pressure situation.
So your choices to me look like this;

1) you could keep the two 120mm side intakes which in my opinion aren't doing much for you. Then add the other 200mm blowhole and see if there is any benefit. This is the max number of fans, intake = 3X120mm + 1 X 200mm. Exhaust = 1 X 120mm + 2 X 200mm. This is approximately equal CFMs on both ends, which creates a 0 or rather low pressure situation. Think of it as 1 atm (atmosphere).

2) keep the intake fans as they are and forget about adding the second 200mm blowhole, which due to its forward location likely won't benefit you. This creates a positive pressure system. This is good. > 1 atm

3) Remove the two 120mm side fans. keep the 200mm and 120mm exhaust, with the option to add a second 200mm exhaust if it does not harm the airflow. Now you have a negative pressure system, which is good. < 1 atm

BTW, it may be quite a bit more complicated than just changing the multiplier and moving vcore to 1.3V. If that works for 4.5 Ghz, then that's great. But don't count on it.
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October 31, 2011 11:50:44 AM

buzznut said:
BF3 max? you'd be looking at two high end video cards for that..Which would require significant cooling. Which makes me wonder what your graphics setup is.

But lets ignore that for now. It looks like the (one) side fan is a good idea. Multiple side fans not so much. The main blowhole and rear exhaust should definitely stay.

Before doing anything else, make sure you have a monitoring program you can work with. CPU-z is a good one, so is speedfan or coretemp. Most Intel users enjoy coretemp.
Regardless of your joy for monitoring, you WILL have to monitor temps if overclocking and especially if overclocking to the level you're talking about. It looks like you've got a decent cooler.

Nice thing is you've got a fan controller for your case fans. This will help in case thermals become an issue.
Next I would take your current config and note the big numbers, that is CPU temp if given, core temps( more important to me), system temp, and maybe GPU. All those can be viewed in Speedfan. Also notable is v core, and any other relevant voltages.

If it isn't too much of a bother, I'd move the A70 into the top exhaust position and note the temps. If it drops any, keep it there. If you don't care because its too much hassle, then forget about it-its likely to be a difference of about 3C max. That can mean alot though for max overclock...

Then you can begin adding fans to see if there are any benefits to doing so. With the Phantom you currently have 1 120mm in front and one in rear exhaust, yes? and a 200mm blowhole and a 200mm side panel intake. You also have two side intakes blowing directly on your hard drive cages. That's a lot of side intake, but what it does do for you is create a positive pressure system which is good.

By adding another 200mm top fan, you'll be bringing the system closer to a 0 pressure situation.
So your choices to me look like this;

1) you could keep the two 120mm side intakes which in my opinion aren't doing much for you. Then add the other 200mm blowhole and see if there is any benefit. This is the max number of fans, intake = 3X120mm + 1 X 200mm. Exhaust = 1 X 120mm + 2 X 200mm. This is approximately equal CFMs on both ends, which creates a 0 or rather low pressure situation. Think of it as 1 atm (atmosphere).

2) keep the intake fans as they are and forget about adding the second 200mm blowhole, which due to its forward location likely won't benefit you. This creates a positive pressure system. This is good. > 1 atm

3) Remove the two 120mm side fans. keep the 200mm and 120mm exhaust, with the option to add a second 200mm exhaust if it does not harm the airflow. Now you have a negative pressure system, which is good. < 1 atm

BTW, it may be quite a bit more complicated than just changing the multiplier and moving vcore to 1.3V. If that works for 4.5 Ghz, then that's great. But don't count on it.

Ok so I did think about having the cpu fan blow up towards the blow hole but I think the fan is too large on the cpu and would not fit with my gpu there. Also, I was planning on OC'ing using the guide below. But with just a bit higher voltages due to many people having bsod right away off that guide. Using the 4.5 ghz part of his guide I was gonna copy that but do my ram to 1600 and volts a little higher than what he said and put it at 1.3 instead. Hopefully that goes well. If it turns out perfect on overnight prime95 and temps go well I wont even attempt to lower the volts or raise the ghz. As for my current fan set-up I'll try that out and if my temps are over well 60c after an hour prime95 such as 64 plus then I'll know to change the fan set-up. I think haha. Isn't an our of prime suppose to be around 55-60C?
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a c 122 B Homebuilt system
a c 172 à CPUs
October 31, 2011 12:35:52 PM

You have a little more room with your temps. Do not exceed 70 C under load.
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October 31, 2011 7:38:02 PM

jsc said:
You have a little more room with your temps. Do not exceed 70 C under load.

Oh okay thank you. I think I got this under control. Will post a new thread if help needed. Thanks guys!
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October 31, 2011 7:42:38 PM

Best answer selected by Zachcuden.
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