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Does anyone have a blowhole at the top?

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Jan 19, 2001
Colorado, USA
Curious who had a blowhole at the top of the case, obviously blowing out. Right now I've got one blowing onto my HSF and getting ready to install one below that blowing on my cards. Wondering if the exit at the top makes a big difference?
Q.) Why don't you install a top fan?
A.) Anyone selling a case with a top fan never tested for airflow. Top fans disrupt airflow and increase temperatures. You never want a top fan under any scenario

read this on 3dcool faq
I put an 80mm fan in a blowhole at the top of my small midtower, which handles most of the exhaust needs. The PSU prevents use of a fan on the back, and doesn't evacuate enough heat to make a difference. Centered above the mobo and behind the drives.the blowhole makes an excellent rising hot air exhaust.
I was wondering if it would redirect airflow. I've already got two exhaust in the rear at top.

Couldn't find FAQ's at 3dcool.com to read more.
You want the airflow over your motherboard and to exit at the rear either through the PSU or also through and additional fan under the PSU. Putting a blowhole in the top of a case diverts the air that should flow over the motherboard and leaves a dead air zone over the hottest part of your computer. The same also applies to fans in full towers mounted above the PSU.
so in your water config where you put the radiator above your powersupply. would it be bettter to isolate that system from the rest of the case...as not to disrupt the airflow below it?
dem1an (Mar 29, 2001 05:43 p.m.):
so in your water config where you put the radiator above your powersupply. would it be bettter to isolate that system from the rest of the case...as not to disrupt the airflow below it?

Good point, I believe this would be a better solution. Water cooling changes the game plan a bit since the main heat source is now being dealt with via a radiator. In my particular case, I have a 120mm blowhole aimed at the video card and voltage regulators, a 120mm intake at the front and a 92mm blowhole on the right side of the case to keep the hard drives cool. I also have an 80mm exhaust fan under the PSU and of course the two 120mm fans on the radiator. All six fans are on LM317 voltage regulators, which allow the airflow in the case to be tuned. My case temp at the motherboard is with in 1 degree of ambient.
I added a 108cfm 120mm Sunon in the left side of my case. And a 55 cfm 92mm Sunon to the top of the case. I did the math. My case now has an "overpressure" of 3 cfm. My 80mm exhaust fan in the upper rear now pulls the same volume out of the case as it did before. The two 80mms on/in the PS pull a little less.
The hottest spot in my case was under the new blowhole fan.

Maybe case geography/geometry makes a difference.

Temps before cutting the case and adding the fans: Room=65F Case=74F CPU=83F After adding the fans:
Room=65F Case=69F CPU=66F
In my air cooled box there is a 120mm intake, 120mm blowhole focused on the board, a 92mm exhaust below the PSU and a 92mm exhaust above the PSU. The motherboard temps always rise if the 92mm exhaust mounted above the PSU is on.
klosters64a (Mar 29, 2001 09:23 p.m.):
Maybe case geography/geometry makes a difference.

In the small midtower I mentioned above, there isn't a spot on the back to exhaust air, so the only real option was to either rely strictly on the PSU fan, or do a top blowhole. As i didn't accurately measure temps beforehand it's impossible to do a before and after, but as stated, the case layout made the top the most viable solution.
Logically, case geometry should make a difference. I can’t comment on a mid tower. The closest thing I have had to one is an old Mac Plus.:)
Can you remove just the top panel of the case? If so, cut out a piece of thick cardboard and add a loose fan to it, tape everything on your case and measure temps. I did this with my left side panel before I cut it up, and just adding one 80mm intake fan low in the side (instead of the extra fan you can add low in the front which is obstructed bigtime), lowered my full load temps below 40C where it was around 47C. If the temps are lower then you know it's ok...
the case I added the blowhole(and 120mm intake fan to) is also a small mid. It does have an 80mm exhaust fan installed in the upper rear behind the CPU. But the PS is a PC P&C Silencer 275, and its fan only moves 23 cfm. I attached an extra ~30 cfm 80mm to the PS's internal grille, but it didn't make a big difference. The blowhole did "steal" a bit of air flow through the PS. When the warranty expires on the PS, I'll be free to replace its quiet fan with a 42.5 cfm Sunon. Until then, the 55 cfm 92mm fan in the blowhole is working well.