Question Need help with fans and rpm's

Apr 23, 2021
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i have 3 intake fans, stock case fans that come with the corsair 5000x, which are sp120's(1400 rpm max) i believe, and i have a 360mm radiator h150i elite capellix with the fans that come with it, ml120's(2400 rpm max) i believe, radiator is mounted on the top with another sp120 running directly from my motherboard and not icue(no space in my commander fan controller) , if left on balanced in icue the radiator fans always spin faster usually roughly 200 rpm faster, my temps are fine but after reading around apparently my exhaust fans should run at lower rpm than my intake fans? just wondering what i should do for fan settings, speeds maybe even moving them around in my case if need?
 
my temps are fine but after reading around apparently my exhaust fans should run at lower rpm than my intake fans?
it depends on the resistance to both incoming and exhausting air.
considering that your radiator fans have to blow through the radiator's fins they are not expelling as much air so the amount of exhaust could still be quite a bit lower than intake.

but if the front panel filters are too dense then the incoming air will also be hampered a bit so this could even out the ratio.
i would probably add another bottom intake if possible.

just test different fan speed curves with different ratios of intake & exhaust and see which gives you the best performance vs noise.
 
Apr 23, 2021
26
3
35
0
it depends on the resistance to both incoming and exhausting air.
considering that your radiator fans have to blow through the radiator's fins they are not expelling as much air so the amount of exhaust could still be quite a bit lower than intake.

but if the front panel filters are too dense then the incoming air will also be hampered a bit so this could even out the ratio.
i would probably add another bottom intake if possible.

just test different fan speed curves with different ratios of intake & exhaust and see which gives you the best performance vs noise.
its not so much the noise and temps, like my temps, both cpu and gpu are good, im just wondering what would be good, ive seen a lot of people saying roughly around 800 exhaust with 1000 intake but that seems like it just wouldnt be enough? could just be me though, the intake fans intake seems to be pretty good with how much air they pull in compared to the noise, they can run at 1200 rpm before noise starts to become noticably loud, ive been running 1400 rpm on my aio with 1200 rpm intake, like im just wondering if their is a downside to having a higher rpm exhaust compared to intake? like you said due to the fans having to blow through the radiator, 1200 intake with 1400 exhaust would be about even i guess? but even then do i want to have a higher intake or does it not matter which has a higher rpm?
 
im just wondering what would be good
just test different fan speed curves with different ratios of intake & exhaust and see which gives you the best performance vs noise
no one can tell you a definite answer of the best exact RPM to shoot for because i doubt anyone has used this case with these components with these exact fans & cooler in your exact environment.
and many others may be willing to sacrifice temperature for silence or vice versa.

a slight positive pressure inside the case is always the best goal because it will help keep the cooler air circulating and help to push the warmed air towards any exhaust points while also keeping dust from entering any openings.
negative pressure can cause the cooler air to be sucked out of the case before it gets to actually cool anything while also pulling in dust through any cracks/crevices/holes.

so you definitely want more air intake than exhaust.
what you need to set your fans to to achieve the perfect setup for your needs will be up to you to determine.
 
Apr 23, 2021
26
3
35
0
no one can tell you a definite answer of the best exact RPM to shoot for because i doubt anyone has used this case with these components with these exact fans & cooler in your exact environment.
and many others may be willing to sacrifice temperature for silence or vice versa.

a slight positive pressure inside the case is always the best goal because it will help keep the cooler air circulating and help to push the warmed air towards any exhaust points while also keeping dust from entering any openings.
negative pressure can cause the cooler air to be sucked out of the case before it gets to actually cool anything while also pulling in dust through any cracks/crevices/holes.

so you definitely want more air intake than exhaust.
what you need to set your fans to to achieve the perfect setup for your needs will be up to you to determine.
yeah of course, im gonna add 3 more intake fans to try and get that positive pressure, would 6 fans running at 1200intake be enough to balance out a 1400 radiator exhaust and create a positive pressure?
 
would 6 fans running at 1200intake be enough to balance out a 1400 radiator exhaust and create a positive pressure?
it depends on the CFM & mm/H2O of the fans and any obstructions they are pushing/pulling through.
some lower quality fans have high RPM value but still have relatively low air pressure & airflow.
again, you would have to experiment with your setup and see for yourself.

you can test the case's air pressure with a thin tissue, feather, etc.
hold it to an opening, not a fan mounting point, and see if it is pulled toward the opening or pushed away.
 
Apr 23, 2021
26
3
35
0
it depends on the CFM & mm/H2O of the fans and any obstructions they are pushing/pulling through.
some lower quality fans have high RPM value but still have relatively low air pressure & airflow.
again, you would have to experiment with your setup and see for yourself.

you can test the case's air pressure with a thin tissue, feather, etc.
hold it to an opening, not a fan mounting point, and see if it is pulled toward the opening or pushed away.
yeah i'll give it a look, thanks for the help!
 

Paperdoc

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To start, you may misunderstand how the fan speeds are "set". The RAD FAN speeds are set by iCUE based on the temperature inside the CPU chip - that is to keep the CPU chip cooled properly. The CASE FAN speeds are set according to a DIFFERENT temperature sensor on the mobo, so it is NORMAL that they will be running at a different speed.

Now, I agree that the ideal situation is small positive pressure inside the case, with dust filters in front of each intake fan. How to achieve is tricky. Any resistance to air flow on a fan (dust filters, rad fins, etc.) reduces the actual air flow delivered by that fan, so you can NOT predict the real air flow from the raw specs for the fan. Thus trying to calculate air flow balance and possible case pressure from specs, speeds and fan count is impossible.

The reason for small positive pressure inside the case is so that any air flow leaking through small openings and cracks will be inside-to-outside, and prevent dusty room air from entering there. You can TEST for this yourself using a smoke tracer technique. You need a small smoke source like an incense stick or a cigarette. Get your system running, at idle conditions for starters. Move your smoke source around the outside of the case near small cracks, ad watch which way the smoke blows, If it is sucked inside slowly, you have a negative pressure inside and it can pull in dust. If the smoke blows gently away from your case, you have a small positive pressure and that's ideal. If the smoke really moves fast, you have a pressure that might be too large, and maybe you could try to balance it a little better. Now change your system workload - say, some common office job, and repeat. Finally, try heavy workload like demanding games and repeat. If you get moderately slow smoke flow away from the case each time, you have it all ideal and need to do nothing more.
 

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