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View Full Version : In or Out? (radiator & fans airflow direction)



eduncan911
06-27-05, 02:20 PM
To save a long spill of my "setup", here's a list to a post of my setup:

http://www.ocforums.com/showthread.php?t=345384

And it's been awesome at 4.2Ghz and 1200mhz FSB.

But lately I've had some gaming lockups during this summer. Doing some recording of the temps, I've noticed my Graphics card getting to 120C! Whoa! The 6800 is said to throttle at 135C, and it's an GTO (O stands for OEM). Wondering if it just doesn't like getting that hot (it's not overclocked). I've stuck a probe into that area and have measured up to 58C ambient right beside the card.

I also noticed my case's ambient was sitting around 42 to 46C (under gaming conditions for a few hours), where my CPU was idle at 34C and maxes at 42C under full HT load!!! LOL. My CPU runs cooler then the ambient temps around it. Intel's specs on the LGA775 says it can not exceed 38C around the VRMs, and also their spec requires air-flow over the VRMs to keep them cool. I have added two 1.8" micro fans doing that job.

I got this resolved by sealing the side "Shark" vents you see in that link above. This forces the air to be pulled in from the front 12cm fan and the 3 12cm fans on the radiator uptop. I'm now at ~33C (Case) and 33C (CPU) temps @ idle, ~36C (case) ~42C (CPU) under full HT load for a few hours (two Prime95s running). Very nice! But I want lower case temps.


Fun time... Now comes the debate. When attempting to improve my temps even farther, I had an idea. Flip the radiator for a little while and pull air OUT from the top. To make sure I could get enough air, I disconnected the rear 12cm case fan, so the air can be pulled from the back, and the front.

This netted as-expected results: ~29C (case) ~39C (cpu) @ idle, ~31C (case) ~48C (cpu) under full HT load for a few hours. That's a big difference both ways.


Bottomline: Pulling air inwards netted lower CPU temps but higher case temps. Pushing air out netted higher CPU temps, but lower case temps.


Ok, I'm done with the spill. Now time for the simple question(s):

What's more important, case or CPU temps? I think I am at a happy medium right now with pulling air-inwards, but wanted to ask you guys.

What should I do? Pull air inwards from the Radiator up top and force out back with the faster-spinning 12cm fan and Card Slot blower?

Or should I try to reverse the air flow, pull-in nice cool air from the back 12cm fan (changing directions) and reverse the upper fans (this will take some work with them wired in series and attached to the radiator)?


I'm thinking I can lower my case temps down a bit further staying as-is (pulling air inwards from the radiator) by installing a Northbridge/chipset WB and adding it to the loop. Running at 1200mhz FSB, that sucker is WAAAY too hot to touch. Running at 800mhz, it can be touched. Major differences in temps and I really think that's a large part of my radiant heat in the case.


Sorry for the long post...

Jas
06-27-05, 02:24 PM
I would pull air INTO the case through the rad, and look to increase your ability to remove air out of the case. thus netting yuo posotive results for both CPU and case temp. You coudl try using any case fans as outputting fans, even the one in the lower front. This woudl probably help.

eduncan911
06-27-05, 02:32 PM
I would pull air INTO the case through the rad, and look to increase your ability to remove air out of the case. thus netting yuo posotive results for both CPU and case temp. You coudl try using any case fans as outputting fans, even the one in the lower front. This woudl probably help.
Good idea.

Just this SharkTower case from ThermalTake isn't the best design. Amongst other complaints I've posted about, one thing is the front fan. Closing the front door sufficates airflow from the front fan (there are no slots to pull air inwards!!!). Much less a filter and an easy way to access the filters. Don't get me wrong, I've loved THermalTake's cases in the past and have set such a high standard with their past cases. But this one.. This one.. Ugh. Part of the reason why I didn't care to cut it all up. lol

During "service" I'm planning on next month (to replace the hoses, get rid of the coorision), I'm going to add in the chipset WB. At the same time, I was looking to improve air flow.

I'll flip the front fan and cut some groovers in the front piece to give it an exit port. Come to think about it, that would be ideal cause of the slot-blower I have in the lower slots pulling air downwards, the rear 12cm fan running at 7.5V (still moving a LOT of air, at very little noise level), and the front fan running at 1500rpms (stock ThermalTake "quiet" fan). The upper fans are running at 4.3V or so.

Are there better 12cm 1" fans that move a lot of air (and very little noise)? I love these Denkis I have in the top and rear. Just they are 38mm wide, too wide to fit in the lower front.

Jas
06-27-05, 02:37 PM
I'm really partial to panaflo fans, but, there is a sunon 120x25mm fan that pushes 90cfm at roughly 45 dba. Pretty popular fan, undervolts well too.