External Exhaust Fan by PCIe Slots

PieEater · 11 Jan 2023 at 19:48

I'm thinking of mounting a 92mm fan externally as an exhaust for my GPU. This will fit quite nicely in the recess in my case (Fractal R6) that houses the PCIe slots and I plan on fitting a cover on the back of the fan to stop anything hitting the blades. I have 2 x 140mm intakes one pointing at the CPU cooler (NHD-15) and one pointing at the GPU, I have the regular exhaust fitted to the rear of the CPU cooler so there is a straight through flow of air and this seems to work well, so was thinking that trying to achieve something similar with the GPU might be worthwhile, although the 3 GPU cooler fans will be swirling air in all directions which may effect things. I was just wandering if anyone had tried this before and whether the results were worthwhile. I guess I am trying to achieve better GPU cooling to allow the card to boost slightly higher and slightly reduce GPU fan noise.

PieEater · 13 Jan 2023 at 08:04

freddie64 said:
You could try removing the remaining PCI covers to help the heated air be pushed out of the back of the case.

Seen this mentioned a few times, but can't remember who came up with it.

Whoever it was seemed very knowledgeable about this type of stuff though.

Thanks that's good advice and I forgot to mention that I have already done this.

PieEater · 13 Jan 2023 at 08:06

ncncore said:
If you have a spare fan why not try it and monitor your thermals, that's really the only way to know in your specific usecase.

I don't have a spare 92mm fan which is why I was asking if anyone had tried it but I've ordered one now so will post the results after testing.

PieEater · 13 Jan 2023 at 10:37

mickyflinn said:
You can still get a pcie exhaust fan probablly sound like a jet engine but it's an option and a blast from the past.

Yeah you can still get them but I want a proper exhaust fan to work with the intake and pull air through the case. Fan has arrived so check back for an update :cool:

PieEater · 13 Jan 2023 at 12:53

So I have the fan fitted, I used black duct tape, and I'm quite pleased with the result.

I tested the setup before fitting the fan by running 3DMarks Stress Test and logging the sensors with HWInfo,
Av CPU 54c
Av GPU 73c
Av GPU Hotspot 95c

Then I did the same after fitting the fan (Av RPM 1450)
Av CPU 53c
Av GPU 73c
Av GPU Hotspot 95c

So at best I saw 1c drop on the CPU presumably by getting ride of some warm air before it could make it up to the top of the case.

I then upped the fan speeds across the board.
Av CPU 52c
Av GPU 72c
Av GPU Hotspot 93c

So looking a bit better but needs some more tweaking.
Next step is to install Asus FanXpert so I can manually tweak the fans on the fly rather than having to go into BIOS each time.
Overall though I'm slightly disappointed that it's not made the immediate noticeable difference I was hoping it would.

PieEater · 14 Jan 2023 at 16:38

After further testing I think my existing cooling was working pretty optimally before I started and the addition of the fan at the PCIE slots made little difference. I suspect this is largely due to having the blanking plates removed and a 140mm intake fan pushing cool air through the case, supplying the GPU fans and pushing warm air out of the unobstructed back. Heat from the back of the graphics card is being rapidly pushed out by the CPU cooler airflow. So it was an interesting experiment but one that I expect will vary from rig to rig so may still be worth trying if you have the time and inclination.

PieEater · 19 Jan 2023 at 09:44

mickyflinn said:
Did you try the fan as intake ?

Nope once I established that the graphics card really didn't benefit from additional airflow I stopped experimenting and just set the lower intake and exhaust to about 600rpm so they are silent but providing a decent through flow of air.

Having the lower fans maxed out made no difference to the GPU but the CPU benefitted by a couple of degrees I'm guessing that the extra turbulence from below diluted the hot air from the back of the GPU but as the CPU is undervolted and has a negative PBO curve it runs cool enough anyhow.

PieEater · 20 Jan 2023 at 08:24

Drumroll said:
Sometimes the easiest way is to simply buy a new case. Some Lancool 215 B Grade or Lancool II Mesh B Grade can do what many extra fans won’t.

I'm very happy with the Define R6, I chose it because of the aesthetics and it's sound dampening. Given my priority for quiet operation I knew there was always going to be a compromise over cooling ability vs airflow orientated cases. The case does have the option to remove the front door and top panel to improve cooling efficiency but at the costs of looks and increased noise which isn't what I want.

PieEater · 20 Jan 2023 at 10:54

LuckyBenski said:
Thing about noise suppressing cases is they often then restrict airflow leading to higher fan speeds. I run a bequiet Pure Base 600 with water-cooling, and with 480mm radiator space it's unreasonably warm (44° liquid temps). There's a whole argument going for mega air flow cases and low fan speeds.

Fans, speeds, noise, and temperature is such a complex multidimensional issue and it seems every individual build needs experimenting to get the best results.

Very true, however things have changed from the good old days of chasing usable performance gains through throwing more volts at components with the resulting additional heat being generated and additional cooling requirements. We now have CPUs and GPUs that can be undervolted to reduce their power draw -> operating temperature -> cooling requirements whilst still providing sufficiently high performance that you wouldn't notice any difference from operating at stock.

PieEater · 1 Feb 2023 at 20:45

SpudMaster said:
Now you've got the fan you might aswell give it ago as an intake. The problem you have when its an exhaust is the gpu fans are sucking air in the opposite direction so both fans are competing for the air. As in intake it will atleast be providing cool air to the gpu fans

bfar said:
I wonder if the GPU intakes are pulling in the cool air before it reaches the rear of the case? The GPU is probably doing the job of that rear fan and pulling the cool air to where it actually needs to be.

I have a 140mm intake feeding fresh air directly to the GPU cooler the idea of the exhaust was to ensure a throughflow so that the fresh air from the front was pulled towards the back of the case allowing the GPU cooler fans to access it. I may try the rear fan as an intake as and when I have the time and motivation possibly in the summer when things start to heat up but right now everything is running pretty cool :cool: