best airflow for the smallest (14l) modded mATX case

[VERiON]

I was planning to move my parts to RAIJINTEK STYX mATX case (see this thread viewtopic.php?f=15&t=69588)

and Luca (thanks again!) suggested me Silverstone SST-ST30SF V1.0 300W PSU - small SFX psu that stays fanless under 55'C

This PSU is perfect for my needs (low power requirements). But instead of buying that PSU and STYX case I started thinking about reusing my really small mATX case that I've had lying around.

Its a generic case that is sold under many brands
https://www.silentiumpc.com/en/silentiu ... q30-black/
It has rather unfortunate design with full-size PSU overhanging CPU cooler that has to be really low profile. But I was using it with pico psu so it wasn't a problem.

The case is exceptionally small - only 14 liters! Smaller than Raijintek STYX!
And for mATX case!

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Anyway... this is my hardware list and usage scenario:


MOBO: GIGABYTE Z97M-D3H (microATX)
CPU: i5-4690K with Thermalright MACHO 120mm (rev A.)
RAM: 4x 8GB
VIDEO: ZOTAC GTX 750 passive

2x 256GB SSD
1x 3,5" in Scythe Quiet Drive enclosure

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USAGE SCENARIO:
I'm a graphics designer and my workflow and type of work means that:

- most of the time: pretty light use of CPU @25% with short spikes @50-100% on all 4 cores
- occasionally CPU @100% on all 4 cores - when encoding a movie or something like this (and I don't mind increased fan noise in that rare cases)
- most of the time GPU is ideling with occasional activity spikes with Photoshop functions that supports GPU acceleration (very rarely, PS is all about CPU)

- I'm occasionally taking the computer to other locations (in a car) - that's why I want it to be fairly compact

- no gaming

- it's a hackintosh (macOS on a pc computer)
- I can control the speed of up to 3 fans (via software) and relate the speed of each fan to the CPU or SYSTEM or GPU temp

- it's running 24/7 because it syncs my work folder to Dropbox (and it takes a while with huge files)
- filtered intake would be a plus (because of 24/7) but I can live without it or with negative pressure scenario

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POWER CONSUMPTION:
currently system (with 120W pico PSU) is using:
when idle: 35W in total
with CPU in stress (GPU in idle): 100W


____________________________________________________


What I'm planning:

- make opening at the bottom of the case for 120mm (or 140mm) intake fan
- intake fan will be blowing towards fanless GTX 750 video card
- psu will be placed like on the attached drawing (should be fanless most of the time)
- CPU will be cooled with big tower heatsink
- fan on CPU cooler will be in PUSH position - 120mm (currently runs on 650rpm all the time)
- opening on the back of the case will be enlarged
- I'll make a shroud from CPU cooler to the opening to prevent hot air from bouncing back into the case
- 3,5" HDD in Scythe Quiet Drive enclosure will be placed near the CPU fan leaving the gap about 3cm (over 2") between the fan and , if I move PSU closer to the video card it shouldn't block PSU exhaust
_____________________________________________________

What do you think?

case-airflow.jpg

Maybe I should ditch the shroud and add 3rd fan as an case exhaust fan? Maybe with the shroud hot air will build up near the back and top of the case?

Maybe I should use only case fan (no CPU fan) this will keep the case well ventilated and CPU cooler is so close to the fan (and so oversized) that it shouldn't be a problem to cool it with case fan only.

[phobus]

I've never seen that case before. The vents on the bottom appear to be pretty small (seen in this video). Edit: never mind, I see now that you already mentioned cutting a bigger hole for the intake.

Is that available in the US? Do you know under what other names I might find it? I'm not having much luck finding it anywhere.

[VERiON]

The only other name that I recall is X2 CUBE MAX
http://www.x2products.com/computer-case ... 1b-cer-u3/
But this is still in Europe IIRC.

In US you can buy slightly higher Rosewill Legacy U3-S
It's US brand for this case:
https://www.aliexpress.com/item/HTPC-MA ... .26.KYku6k

[phobus]

Aw, okay. I've seen that Rosewill case before but I like the front PSU layout better for some reason. It also seems to be discontinued.

[VERiON]

I've measured the back.
120mm fan would be a perfect fit for the back.

I can cut the cover from the 1mm metal sheet (with the cut-out for a 120mm fan) and glue it to the back with epoxy. Effectively sealing all of the openings and strengthening the back a little bit.

white = metal sheet back cover
red= 120mm fan cut-out

[quest_for_silence]

Maybe I should ditch the shroud and add 3rd fan as an case exhaust fan? Maybe with the shroud hot air will build up near the back and top of the case?

Maybe I should use only case fan (no CPU fan) this will keep the case well ventilated and CPU cooler is so close to the fan (and so oversized) that it shouldn't be a problem to cool it with case fan only.

An active exhaust is almost always necessary to prevent heat build up (and often a shroud between the CPU heatsink and the rear cut-out works against the case heat evacuation): said that, IMHO you've just to try if, within your usage pattern, the rear exhaust fan isn't that mandatory (said differently: if your system will run hotter but not that hot).

With reference to a pull fan for the CPU heatsink, at the same time acting also as a case exhaust, usually that leads to a somewhat higher CPU temp: again, you have to try if (according to your usage pattern) CPU temp will be higher, but not by much.

[VERiON]

and often a shroud between the CPU heatsink and the rear cut-out works against the case heat evacuation


Thats what I thought. Thanks for the confirmation.

Right now I have it configured like this:
- a fan on pull position on i5-4690K cooler with the original back opening for the full atx psu
- no intake fans
- no discrete graphics cards
- pico psu

and CPU temp hovers below 50'C, but it is with side panel open.
With the side panel closed heat builds up really quickly (a whole case gets warm to the touch (I'd say about 45'C).

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I'll start observing the temp with side panel closed in steps like this:

STEP 1
- CPU fan
- case exhaust fan (back)
- observe the temp

STEP 2
- CPU fan
- case exhaust fan (back)
- case intake fan (bottom)
- observe the temp

STEP 3
- case exhaust fan (back)
- case intake fan (bottom)
- observe the temp

STEP 4
- case exhaust fan (back)
- observe the temp

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STEP 4 is just for fun of experimenting, because intake fan is a good idea IMHO. Especially with the room for 140mm intake fan I can make this setup pressure positive.

I have high hopes that setup from STEP 3 will work good enough (temp wise) - that is only intake fan at the bottom and exhaust fan at the back of the case.

[VERiON]

Here are my results for different setup testing.

Using 2 120mm fans for intake at the bottom and exhaust at the back.
Keep in mind that this was a rather ghetto setup - without cutting the case floor and without making a bigger opening at the back.
That means:
- bottom fan intake was restricted (about 50% of the fan area was actual opening - holes in the bottom of the case
- back fan was just "standing" on the back of the graphic card, and the opening at the back was too small - only about 70% of the fan "visible" though the hole

temps are in celsius
"crashed" means that PC just shut itself off from overheating - possibly because of PICO psu (el-cheapo equivalent) overheat

I've used GT240 vid card temporarily, because I've lent my GTX750 to a friend for testing.
All test was @30% CPU inducted by running 1 instance of yes > /dev/null & terminal command

Both fans was 120mm from Thermaltake Macho 120 rev A. cooler

temp_test.png

my conclusions:
- case ventilation is the king!
- I can ditch CPU fan (+7'C more with exhaust only fan, the same speed)
- closing the case with exhaust fan makes enough "draft" to cool GPU -8'C
- intake fan makes almost no difference, the only use would be for filtered intake with positive case pressure

- with the properly mounted back exhaust fan in the widened opening this should be even better, more pressure near the CPU heatsink and +30% more fan performance (not obestructed) it would allow me to lower the exhaust fan speed from 1000 > 700 rpm in all scenarios where 1000 rpm was needed - or maybe I'm wrong with that assumption?

What do you think about my conclusions?
Am I missing something?
Should I ditch the intake fan (looks like it makes no difference)?

IMPORTANT!
exhaust fan running @1000rpm was absolutely unbearable for me for normal work - so it's a viable option only for occasional high CPU usage (100%@4cores) - like rendering or encoding.
so I'm looking for a solution that will allow me to lower the exhaust fan (and all others) to 700rpm

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UPDATE

I've just checked - when running 100% CPU on all 4 cores and exhaust fan @1200rpm - CPU temp jumps @60'C and starts slowly creeping up and up.
It reaches 66'C after 10min - and then PC shuts itself down. PC case temp is @35'C so it's a problem of heat build up. I'll check it again with proper PSU (not that pico psu
I'm using right now).

But for normal work in Adobe CC - CPU temp hovers around 40'C with just the exhaust fan @600rpm

So far my plans are:
- cut out the hole on the back of the case to properly mount 120mm fan
- seal all other openings, except the bottom intake
- add Noiseblocker M12-S2 fan as an exhaust (normally @600rpm with the option to ramp up when needed)
- add Scythe Glidestream (2x cheaper) as a CPU fan in push position just in case - normally off, but starting on high CPU usage (rarely)

[VERiON]

OK. More tests behind me

This time running @100% on all 4 cores.

temps-v2.jpg

my observations:

FOR NORMAL WORK (with YT playing music in background)
with case exhaust @650rpm only (CPU fan off) everything is perfectly ok, temp hovers at around 40-48'C with spikes up to 65'C when making CPU intensive work (like resizing really big photoshop file with multiple layers and effects) but there are just short bursts with all cores @100% and can't heat up CPU more than 65'C (ends too quickly).

FOR SUSTAINED CPU "burn" (more than 30min)
- I have to ramp up CPU cooler fan, because without it CPU is overheating quickly
- spinning case fan above 800rpm doesn't have almost any effect on CPU temp (and case temp stays low even @650rpm)
- best temp/noise ratio is when both case fan and cpu fan are running @800rpm

It's all without cutting the case so:
- exhaust is still obstructed (30% blocked), so I'm hoping for a little better results when finished
- bottom intake is not enlarged (only case bottom perforation)

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Now I pretty much know what I want to do:
- exhaust fan @650 rpm (or lower when I switch the fan) with the option to ramp up to 800rpm when cpu is above 55'C
- CPU fan off with the option to ramp up to 800rpm when CPU is above 65'C
unless I'm missing something. If so - please let me know .

But I'm not sure if I should do something with intake.
It looks like mobo and hdd stays cool no matter what - so additional intake fan is not needed.
The only reason for intake fan would be positive pressure.

What do you think? I can make bottom opening for 140mm fan and mount aftermarket wire magnetic dust filter at the bottom.
I would like to use GlideStream 140 fan - because it's not expensive and has (almost) octagonal frame - so it would be easier for me to make a cut-out using only dremel straight cuts (maybe not that important... and with square frame fan it would be even easier to cut ).
But it will be in horizontal position - if you know if this fan has a problem with horizontal position (noisier/buzzing/clicking/etc) - please let me know.

[quest_for_silence]

But I'm not sure if I should do something with intake.
It looks like mobo and hdd stays cool no matter what - so additional intake fan is not needed.
The only reason for intake fan would be positive pressure.

The very best reason is to not re-circulate hot air. Do you need that? I can't help.

But it will be in horizontal position - if you know if this fan has a problem with horizontal position (noisier/buzzing/clicking/etc) - please let me know.

Any sleeve bearing fan has problem running that way (bottom intake or top exhaust), at least reliability-wise.

[VERiON]

The very best reason is to not re-circulate hot air. Do you need that?

Not really. Cooling is not the problem - temps (mobo and hdd) are actually better with case closed so there is enough cool air in case right now.
Everything is cool (pun intended) without the intake fan.

But I was wondering if I should put filtered intake with 140mm fan to keep the dust from entering the case.
I've always had negative pressure case and dust was never a real problem for me. But this computer will be running 24/7 so maybe I should aim for positive pressure setup.