Exhaust fan beneath GPU- Pics/test results

Nobu

Supreme [H]ardness
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Jun 7, 2007
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I'm tempted to order 2 40mm fans and mount them to the left where a normal person would mount a resivour.

A 80mm was just a touch too wide.

Wonder if I could sand down the edges...

Then I'll try the cardboard duct idea you guys had for fun:p
They make 70 and 60mm fans, too, if it's just a bit too big. Noctua has a 60mm fan, but not 70. Couldn't find an arctic fan in either size.
 

craigdt

[H]ard|Gawd
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Oct 27, 2016
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View attachment 273336


I know that I'm resurrecting a 2 year old thread, but it occurred to me when building in my new Fractal Define 7 XL that I could actually fit a 120mm fan underneath my GPU if I move the GPU to the top slot. A regular 120mm fan was a bit too thick but a slim 120mm (Scythe Kaze Flex Slim RGB) fan fit perfectly.

It had a small effect on my load GPU temps - they're a little slower to rise but the overall temp only went down about 3c, but it had a huge effect on my CPU temp, -5c during a game with gpu load. Probably because the heat from the gpu is being sucked out the back of the case instead of just recirculating inside the case to slowly rise through the CPU heatsink. The only NVME drive that had a noticeable temp decrease was the one on the riser card, probably because its directly in the airflow. The three motherboard based nvme's didn't change temps at all but that's probably due to the giant heatsink plate without any fins. Chipset temp is also basically identical, I think the 120mm fan is too far away to help with that.

Overall for something that took about a minute to install and test it was a worthwhile test and I'll likely keep it installed until I fill the lower PCI-E slots.

I uhh, forgot to get side pics before I tested, but I'll probably snap some later. It's impossible to see inside my case during its normal operation.

View attachment 273337
But here's a pic from the front, through one of my intake case fans. I think it shows perfectly how well it just slots underneath the GPU. I don't even have it mounted or tied down by anything, friction keeps it in place perfectly.
Yes, I personally find it amusing to have the only RGB in my entire case below the gpu in the back of the case. That was on purpose.

Cool- I'm always interested by alternative layouts that are somewhat experimental in nature.
Thanks for sharing!


As a follow up, I eventually:
-Removed the existing 92mm fan and added 2 80mm just to the left of the gpu as additional exhaust. Made them fit.

The 2 actually did a very good job in pulling heat from the 1080ti and 1060 3GB I had crammed in there.
No numbers to share, but they also added some fan noise, since they ran at full blast all the time.
 

pendragon1

Fully [H]
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Oct 7, 2000
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22,969
added 2 80mm just to the left of the gpu as additional exhaust. Made them fit.
molex? if so you can run them at 5v by swapping the red and yellow wires on the molex plug they go into. only do it with the last plug at the end of the psu cable though. if theres more in the chain the voltage is reversed until the end plug.
 

TheSlySyl

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May 30, 2018
Messages
575
Finally moved my case to a point where I can get a picture of the inside.
ixZ2-l7AoctEI51P2G3TJpdw=w2597-h1947-no?authuser=0.jpgP7Rk_xsGlsNHLlunQNXEkoCA=w2597-h1947-no?authuser=0.jpgk8QmzIjq5Dajv7SgXH6MDakw=w1461-h1947-no?authuser=0.jpg
That last one is for an idea of just how close the fan is to the fan on my Arctic Accelero III Extreme.

Yet again, didn't affect GPU temps that much at load, but it was a huge boon to CPU temps because it sucks out the hot air the GPU spits out instead of recirculating it inside the case.
 

TheSlySyl

Gawd
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May 30, 2018
Messages
575
Are you removing all those pci case slots behind that lower fan?
They're super, super open in this case. Given how often that I'm blindly digging at the rear of my case for plugging my GPU in, I figured it was better for my fingers to just leave them in.
1599673186210.png
 

Rev. Night

Limp Gawd
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Mar 30, 2004
Messages
410
Interesting what case is that? In my Fractal Design Define C, the slots are solid with no airholes
 

chameleoneel

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Aug 15, 2005
Messages
3,422
Not a fancy test, just my anecdotal results.

To me, the heat produced by the GPU, being forced down, back into the case, instead of forced out the back is a general source of unnecessary heat.

So, I had a spare Arctic F9 92mm fan and placed it at the rear of my case, directly under the 1080ti.

The idea being to exhaust (some) of the hot air out of the back of the case.

The 92mm fan wedged perfectly under my EVGA 1080ti SC2 and the bottom of my Phanteks Enthoo Pro M.

Supposedly the little fan moves 42cu ft of air, and it certainly is impressive for how small it is.

Preliminary testing showed a 5 degree drop with my GPU fans at 25% and 3 degree drop with fans at 60%. This was with a +99core and +500 memory overclock, on a heavy (gasp) mining workload.

Is this earthshattering? No.

But it's enough of a difference for me to leave it in there.

It also might allow to drop the GPU fan rpms a bit, to decrease the noise. The Arctic F9 92mm is virtually silent.

The won't work if you want to populate the other pci slots, obviously.

It also might help with GPU sag :p

Pic
View attachment 61977
now try the fan as an intake, instead of an exhaust. I bet you see even better temps.
 

pendragon1

Fully [H]
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Oct 7, 2000
Messages
22,969
I think I read that gpu at that location as an intake actually adds heat
it will make the gpu run cooler as its getting fresh air but it would also help puch hotter air from the gpu to the top of the case. if you have good front to back/top airflow the difference is minimal, a couple C. its what ive been doing for years. until i went gpu aio and now with my 5700(no aio) which doesnt seem to need it.
 

Rev. Night

Limp Gawd
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Mar 30, 2004
Messages
410
I would do it, but do the gpu fan bracket i built, I don't have the room. From the pic, that 92mm fan takes up 5 slots.
 

TheSlySyl

Gawd
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May 30, 2018
Messages
575
1599771726557.png

Each cutout is roughly 15.88mm tall, with a small gap.
My case, being a monster, has 9 PCI slots instead of the typical 7. Which, at 15.88mm each is simple math at how I got a 120mm fan in there instead of a 92mm.
 

somebrains

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Nov 10, 2013
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The Lancool 2 Mesh will drop gpu temps from a psu shroud intake fan. It's unusual in that it has perforated side panels in the psu chamber.

Iirc I saw this first with Caselabs, maybe TT?

Cheap and dirty version of this would have been HAF cases with a side intake fan.
 

doyll

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Feb 4, 2012
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I've found just removing all PCIe slot covers from all unused PCIe slots, having front of case full of intake fans with all openings not covered by fans in front half of case blocked off so so the air intake fans are pushing into case has to flow through case and out back instead of leaking around fans going in circles or out top/bottom almost always supplies components wtih cool air. Once in a great while an exhaust fan will give a couple degrees lower temps, but not very often.

Key is having case airflow optimized so cool air flows to components and pushing heated component exhaust on back and out of case is best. The less turning and obstructions (cables, HDD cage, etc) there is in airflow the less turbulence there is so less heated air mixing with an warming up cool intake airflow to components.
 
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