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Exhaust fan beneath GPU- Pics/test results

craigdt

craigdt

[H]ard|Gawd
Joined
Oct 27, 2016
Messages
1,075
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
wwMrveC.jpg
 
Some people question why I mount my PSU "upside down" (fan side up) in my microATX build; it's for this very reason. I experience a 3-8 degree drop in GPU temps, depending on the workload.
 
don't the fans push air in to the heat fins?

all you are doing is starving them, no?

or pulling cool air toward them.
 
Master_shake_ said:
don't the fans push air in to the heat fins?

all you are doing is starving them, no?

or pulling cool air toward them.
Click to expand...

No, the fans on the GPU blow the hot air down, away from the fins/chip.

Then, the little fan I added exhaust that hot air out of the case, instead of re-circulating into the case.

Edit- Derf- as seen below by the nice gentleman, I said this wrong. The GPU fans suck cool air in through the fins.

The additional exhaust fan is certainly not starving the GPU fans- it led to overall cooler GPU temps.
 
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craigdt said:
No, the fans on the GPU blow the hot air down, away from the fins/chip.

Then, the little fan I added exhaust that hot air out of the case, instead of re-circulating into the case.
Click to expand...

so they suck air through the fins and out the bottom?
 
craigdt said:
No, the fans on the GPU blow the hot air down, away from the fins/chip.

Then, the little fan I added exhaust that hot air out of the case, instead of re-circulating into the case.
Click to expand...
I'm almost positive you're wrong on that... Your little case fan is probably helping by pulling cool air across the face of the card so the card has access to cooler air.

The card's fans definitely blow air into the fins, towards the card, unless you modded them to run backwards.
 
VanGoghComplex said:
I'm almost positive you're wrong on that... Your little case fan is probably helping by pulling cool air across the face of the card so the card has access to cooler air.

The card's fans definitely blow air into the fins, towards the card, unless you modded them to run backwards.
Click to expand...

Correct- yes- they are sucking cool air in, exhausting hot air them through the fins. Clearly, I stated that wrong.

The little fan is definitely removing additional hot air, allowing the card to access overall cooler air.

For further testing, I'm tempted to move the GPU down a slot and move the exhaust fan on top, just underneath the large 140mm exhaust fan.

Maybe it doesn't matter where its positioned- maybe simply the additional exhaust capabilities decreases overall temps.

Alternatively, I could spin the 92mm fan around and make it an additional intake fan, further feeding the GPU with more cool air.

That seems like it would actually decrease overall airflow, but might be worth testing, for laughs.
 
craigdt said:
Correct- yes- they are sucking cool air in, exhausting hot air them through the fins. Clearly, I stated that wrong.

The little fan is definitely removing additional hot air, allowing the card to access overall cooler air.

For further testing, I'm tempted to move the GPU down a slot and move the exhaust fan on top, just underneath the large 140mm exhaust fan.

Maybe it doesn't matter where its positioned- maybe simply the additional exhaust capabilities decreases overall temps.

Alternatively, I could spin the 92mm fan around and make it an additional intake fan, further feeding the GPU with more cool air.

That seems like it would actually decrease overall airflow, but might be worth testing, for laughs.
Click to expand...
It'll depend on the rest of your case configuration, but if it's placed somewhere that the back end has good unobstructed access to ambient air, you'll probably see good temps with the little fan as an intake located below the card. I don't think you'll see much improvement over normal if you put the little fan above your card, that's just a guess on my part tho. =)
 
sorry but that's nothing new to me. nice build though! got anything cooling your mobo's vrm?
 
okay another update:

This is via a quick 5 minute GPU workload, GPU fans at 25%.
I let the card cool to 39 degrees before each run.

92mm fan as exhaust- 75 degrees
No 92mm fan- 77 degrees
92mm fan as intake- 79 degrees

I'll likely run these same scenarios with the fan set at 60% later.
 
craigdt said:
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
Click to expand...
Nice bit of work.
Don't pay any attention to the trolls. You would be surprise how many people have no idea how their computers cool. Everyone starts out not knowing anything. The smart ones are the ones doing things like what you did to learn.

If you remove all PCIe slot cover from back of case you will likely see another drop in GPU temps.

Yeah, the F9 is generating better front to back airflow below GPU.

What is your case fan setup?

You might find moving the rear exhaust to front so you have 2x 140mm front intakes will give you better temps.
 
pendragon1 said:
sorry but that's nothing new to me. nice build though! got anything cooling your mobo's vrm?
Click to expand...

the biggest problem with AIO's imo.

i reversed the fans on my overhead 240 rad just to have some airflow over mine.

by reversed i mean made them pull air down over the board.
 
doyll said:
Nice bit of work.
Don't pay any attention to the trolls. You would be surprise how many people have no idea how their computers cool. Everyone starts out not knowing anything. The smart ones are the ones doing things like what you did to learn.

If you remove all PCIe slot cover from back of case you will likely see another drop in GPU temps.

Yeah, the F9 is generating better front to back airflow below GPU.

What is your case fan setup?

You might find moving the rear exhaust to front so you have 2x 140mm front intakes will give you better temps.
Click to expand...

I have 2x 140mm intakes, 1x 140mm exhaust and my AIO mounted up top, blowing hot air out.

Then added the little 92mm exhaust

Q9U9wLb.jpg
 
The hot gpu air is being blown horizontally out of the card on the side with the logo and the side toward the drive bays.
put a duct on those sides, leading to the big grated area right next to where the 92 is. Put the 92 at the end of the duct blowing out through the grate. block off where the 92 is now.

Cereal box and duct tape = quick proof of concept duct.

Becha that'll help
 
honegod said:
The hot gpu air is being blown horizontally out of the card on the side with the logo and the side toward the drive bays.
put a duct on those sides, leading to the big grated area right next to where the 92 is. Put the 92 at the end of the duct blowing out through the grate. block off where the 92 is now.

Cereal box and duct tape = quick proof of concept duct.

Becha that'll help
Click to expand...

Dude- my wife would lose her mind if I starting duct taping cardboard in my new rig :ROFLMAO:

It would be a fun proof of concept though. Maybe she wont notice...

I do wish I didn't have to have my Blu-Ray player installed though- I could potentially add 2 more fans, I think.

Also have a spare 80mm fan that wont quite fit in the grated area, just to the left of the PCI... really want to fit another fan in there somehow.
 
i would run that cardboard tunnel from the front fan to your 92. id bet that would give a nice drop in temps. didnt someone used to sell ducts made specifically for that?
 
Gravity

Edit: maybe a small strip of double sided tape on the bottom?
 
I guess it's easy to leave it unsecured but I'm a klutz so I may forget it is when moving / working in the case. Interested in this since I have spare fans lying around.
 
they used to use air "tunnels" for the cpu and sometimes for the gpu, but have pretty much removed them with modern designs because it really did not help to only allow air to come from a specific direction, directed air is always a good thing, but, by ducting a fan prevents it from getting all the air it possibly can or causing unneeded turbulence it can work against the cooling ability and/or make the fan work harder to achieve the same.

well, that is unless your fan moves 100s of CFM at earsplitting levels ^.^

fan below gpu, that might help "sometimes" but can also cause overspin on the fan(s) which can wear them out sooner..a fan forced to spin wears out just like a fan prevented from spinning.

PSU pulling hot air into it AND having to deal with its own heat (push out back) not best idea IMO, sure it helps some components stay cooler but likely also wears out the psu somewhat sooner (more heat, faster wear out for most electronics especially ones that have capacitors/vregs)

I think this is the reason most cases these days are built with PSU sucking in its own air and venting out as well. A number of years now, most cases I have seen do not have PSU in top of case to "help" ventilate, there has to be more than one reason, maybe because they realized it is "not good"

a system can generate a bunch of heat (obviously) the PSU powering that system also generates a lot of heat, to help cool one while increasing the other can only lead to bad things happening (failed fans, things dying from excess heat etc)

pretty sure cpu/gpu can handle a higher range of heat than most PSU are built for, I personally have not had a PSU blast air out like most cpu or gpu heatsinks over the years (foor for thought) a low power system probably wouldn't matter much, likely not a good idea for a medium to high power "gaming" system though..

-------------------------------
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I know many years ago I used a pci slot blower which helped gpu temps a wee bit, but it did not seem to help much at all with noise levels as well it promoted extra dust being sucked in from the back from all those wee holes on pci slots and backpanel in general..dust is the enemy for a variety of reasons.

finally, for the AIO pulling air "down" and blasting over the mobo...that is very odd if you think about it, that means the one exhaust fan has to contend with a crap load of heated air (likely from overclocked components)

nice builds though (even if I hate Nv with a pasion) o7

--------------

to secure fans, zipties or velcro...likely ziptie is "easiest" as they can be left snug enough to hold and not damage anything and removed easily enough if left a "bit" loose so can "clip them".
 
mda said:
I guess it's easy to leave it unsecured but I'm a klutz so I may forget it is when moving / working in the case. Interested in this since I have spare fans lying around.
Click to expand...

Yes- the way it's wedged in there, it 'aint goin' nowhere.

If one was really concerned, they could easily use a couple screws and small washers through the back of the PCI slot covers.
 
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
 
Or just take the front panel off of case, that's the uber restrictive side vented front panel design. Or make sure you're using High Static Pressure fans up there to adjust for the right angle intake path.

But a cool idea, if you have the equipment. (pun intended)
 
I want to know how you get such low temps out of the 1080Ti with 25% fan. I have the EVGA 1080Ti SC Black, same cooler as yours without the one fan at a time thing. It's in a Coolermaster ATCS 840 that is basically a giant wind tunnel with positive pressure. I have 2 120mm top intake fans, a 120mm front intake fan, a 120mm bottom intake fan, and a 230mm front intake fan. The power supply is on the bottom and intakes from there and exhausts out the back. There are 2 120 mm fans behind the drive cage that push air from front to back. The only exhaust fan I have is a Gentle Typhoon 1850 in the GPU cooler box which basically hangs off the back of the case and covers the entire PCIE slot area. It pulls air past the GPU and exhausts it out the back, very similar to what you are doing. If I run Unigine Heaven or Superposition at stock settings, I get 75C on the GPU and the fan is running at 2200 or so RPM which is in the 50 to 60 percent range.
 
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kamikazi said:
I want to know how you get such low temps out of the 1080Ti with 25% fan. I have the EVGA 1080Ti SC Black, same cooler as yours without the one fan at a time thing. It's in a Coolermaster ATCS 840 that is basically a giant wind tunnel with positive pressure. I have 2 120mm top intake fans, a 120mm front intake fan, a 120mm bottom intake fan, and a 230mm front intake fan. The power supply is on the bottom and intakes from there and exhausts out the back. There are 2 120 mm fans behind the drive cage that push air from front to back. The only exhaust fan I have is a Gentle Typhoon 1850 in the GPU cooler box which basically hangs off the back of the case and covers the entire PCIE slot area. It pulls air past the GPU and exhausts it out the back, very similar to what you are doing. If I run Unigine Heaven or Superposition at stock settings, I get 75C on the GPU and the fan is running at 2200 or so RPM which is in the 50 to 60 percent range.
Click to expand...

i would try running your fronts, bottoms and sides as inlet. top and back as exhaust. thats usually the best airflow for most cases. it sounds like your gpu is starved due to so many inlets and not enough exhaust pulling the heat out.
 
kamikazi said:
I want to know how you get such low temps out of the 1080Ti with 25% fan.
Click to expand...

The magic of a $6, 92mm exhaust fan :ROFLMAO:

I just ran Heaven at 1440p, everything set to max, with fans locked in at 50% speed, and it hit 67 degrees.

With Heaven at Basic, fans locked into 50%, it his 52 degrees.
 
I agree, that front is about as good as it gets with a grill. But grill mesh is more restrictive than most people realize. Even the least restrictive hex mesh has about 80-81% open area and round hole mesh has much more blocked leaving it with about 50-60% open area .. and the turbulence created by the mesh also increases airflow resistance.
Image below has data on mesh open area.
 

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doyll said:
I agree, that front is about as good as it gets with a grill. But grill mesh is more restrictive than most people realize. Even the least restrictive hex mesh has about 80-81% open area and round hole mesh has much more blocked leaving it with about 50-60% open area .. and the turbulence created by the mesh also increases airflow resistance.
Image below has data on mesh open area.
Click to expand...

Thanks for the info- very interesting.

Is there a front panel design that flows better? That isn't mesh?

Maybe I'll run some tests with the front panel off tonight. Sounds fun
 
craigdt said:
Thanks for the info- very interesting.

Is there a front panel design that flows better? That isn't mesh?

Maybe I'll run some tests with the front panel off tonight. Sounds fun
Click to expand...
Hex pattern mesh flows more air because the mesh is all same thin lines instead of a bunch of round holes. But the bottom line here is with good pressure rated intake fans the mesh you have is fine.
 
hititnquitit said:
i would try running your fronts, bottoms and sides as inlet. top and back as exhaust. thats usually the best airflow for most cases. it sounds like your gpu is starved due to so many inlets and not enough exhaust pulling the heat out.
Click to expand...

I like to keep positive pressure to avoid so much dust. Perhaps I could swap one fan on top from intake to exhaust. There is room up there for 3 so I could put the one at the front as an intake and leave a blank, then use the one at the very back as exhaust. If you've ever seen an ATCS 840 in person, it's huge. There's also plenty of openings for air to come in. I really don't think the GPU is starved for air at this point. I do notice a drop in temps when I crank the exhaust fan on the back that pulls air directly through the GPU.
 
1598468698989.png



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.

1598468736716.png

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.
 
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