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Fan speed and CPU temperature

Mark J.
By Mark J.
in Cooling
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Posted

Hello,

 

I have been fiddling around with fan speeds and came across what is seemingly a paradox of sorts.

 

I changed my BIOS settings so that the fans in my Fractal Design Torrent case follow a less aggressive curve (from “normal” to “silent”).

 

Now I see temperaturs sitting around 5-7 degrees celcius lower which leads to the following question:

 

Is it possible in certain scenarios that lower fan speeds can lead to lower temperatures? Wondering if a fan speed can be so ‘aggressive’ that warm air is just pushed around inside the case rather than forced out and that this can lead to higher temperatures as long as the case temperature is not consistent (in that the case is not filled up with air being roughly the same temperature)?

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Posted
55 minutes ago, Mark J. said:

Hello,

 

I have been fiddling around with fan speeds and came across what is seemingly a paradox of sorts.

 

I changed my BIOS settings so that the fans in my Fractal Design Torrent case follow a less aggressive curve (from “normal” to “silent”).

 

Now I see temperaturs sitting around 5-7 degrees celcius lower which leads to the following question:

 

Is it possible in certain scenarios that lower fan speeds can lead to lower temperatures? Wondering if a fan speed can be so ‘aggressive’ that warm air is just pushed around inside the case rather than forced out and that this can lead to higher temperatures as long as the case temperature is not consistent (in that the case is not filled up with air being roughly the same temperature)?

What case do you have? What CPU cooler are you using? Where are your fans installed in your case?

I might be experienced, but I'm human and I do make mistakes. Trust but Verify! I edit my messages after sending them alot, please refresh before posting your reply. Please try to be clear and specific, you'll get a better answer. Please remember to mark solutions once you have the information you need. Expand this signature for common PC building advice, a short bio and a list of my components.

 

Common build advice:

1) Buy the cheapest (well reviewed) motherboard that has the features you need. Paying more typically only gets you features you won’t use. 2) only get as much RAM as you need, getting more won’t (typically) make your PC faster. 3) While I recommend getting an NVMe drive, you don’t need to splurge for an expensive drive with DRam cache, DRamless drives are fine for gamers. 4) paying for looks is fine, just don’t break the bank. 5) Tower coolers are usually good enough, unless you go top tier Intel or plan on OCing. 6) OCing is a dead meme, you probably shouldn’t bother. 7) "Bottlenecks" rarely matter and "Future-proofing" is a myth. 8) AIOs don't noticably improve performance past 240mm.

 

Useful Websites:

https://www.productchart.com - helps compare monitors, https://uk.pcpartpicker.com - makes designing a PC easier.

 

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He/Him - I'm a PhD student working in the fields of reinforcement learning and traffic control. PCs are one of my hobbies and I've built many PCs and performed upgrades on a few laptops (for myself, friends and family). My personal computers include 4 windows (10/11) machines and a TrueNAS server (and I'm looking to move to dual booting Linux Mint on my main machine in future). Aside from computers, I also dabble in modding/homebrew retro consoles, support Southampton FC, and enjoy Scuba Diving and Skiing.

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1) When I was 3 years old my favourite toy was a scientific calculator. 2) My father is a British Champion ploughman in the Vintage Hydraulic Class. 3) On Speedrun.com, I'm the world record holder for the Dream Bobsleigh event on Mario & Sonic at the Olympic Winter Games 2010.

 

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Posted (edited)
23 minutes ago, Mark J. said:

Two large fans are pulling from the front, three are pulling from beneath the GPU.

That's a lot of air intake.

Do you have enough surface for exhaust ?

Edited by leclod

I'm willing to swim against the current.

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Posted (edited)
7 minutes ago, Mark J. said:

My bad, the three fans beneath the GPU are exhausting.

So you're taking air away from the gpu ? usually it's the contrary

(that alone could explain your issue)

Edited by leclod

I'm willing to swim against the current.

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45 minutes ago, Mark J. said:

My bad, the three fans beneath the GPU are exhausting.

you want intake on the front and bottom and exhaust from the back and top.

proud owner of a AMD Athlon 64 cpu

PSU tier list: https://docs.google.com/spreadsheets/d/1akCHL7Vhzk_EhrpIGkz8zTEvYfLDcaSpZRB6Xt6JWkc/edit?gid=1973454078#gid=1973454078

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1 hour ago, Mark J. said:

My bad, the three fans beneath the GPU are exhausting.

At a guess, maybe at faster speeds, these exhaust fans were taking away more of the cooler intake air from the front before it could do its job & flow from front to back over your components.

 

3 hours ago, Mark J. said:

I changed my BIOS settings so that the fans in my Fractal Design Torrent case follow a less aggressive curve (from “normal” to “silent”).

Did you take note of the fan speeds before & after you did this? Did ALL fans decrease their RPM & was the ratio of intake:exhaust RPM the same before & after the change?

https://au.pcpartpicker.com/b/Tw9G3C

 

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On 5/20/2025 at 9:40 PM, Ralfi said:

At a guess, maybe at faster speeds, these exhaust fans were taking away more of the cooler intake air from the front before it could do its job & flow from front to back over your components.

 

Did you take note of the fan speeds before & after you did this? Did ALL fans decrease their RPM & was the ratio of intake:exhaust RPM the same before & after the change?

Thanks for your input. It very sounds plausible, at least until I realized all the fans are actually puling air into the case.

There are no exhaust fans. My bad for the abundance of misinformation on my part.

 

I can't monitor the fan speeds as they are connected via a hub (apparently that is a thing with the Fractal Design Torrent, sadly).

 

Is is possible for the fans to be pulling too much air into the case despite there being to exhaust fan(s)? That would be really weird, but maybe there are so aerodynamic factors at work or some such I am not taking into consideration?

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1 hour ago, Mark J. said:

Is is possible for the fans to be pulling too much air into the case despite there being to exhaust fan(s)? That would be really weird, but maybe there are so aerodynamic factors at work or some such I am not taking into consideration?

Well, you always have hot air you need to get rid of.

 

If you have no exhaust fans, then the cool air coming in, will swirl around, increasing in temperature & unable to exit the enclosure with any efficiency. As a result, your case temperature may slowly increase over time.

 

You need to help replace the air in your case whilst letting the cool air do its job - enter, hit your components at its coolest temperature & then be escorted out before it heats up, then a new batch of cool air replaces it, rinse & repeat…

https://au.pcpartpicker.com/b/Tw9G3C

 

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Posted

He is in a Torrent, air does not just swirl around, it is front to back only. You don't need an exhaust fan in a Torrent..

AMD R9 9900X | Thermalright FW PRO, 3x TL-H12-X28, 3x TL-P12

Asus Strix X670E-F | 32GB Lexar Ares @ 6400 30-36-36-68 1.55v

Zotac 4070 Ti Trinity OC | WD SN850, SN850X, 3x SN770, 6TB

Asus PA602, 2x 200x38, 1x 140x28 | Seasonic Vertex GX-1000

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5 minutes ago, freeagent said:

He is in a Torrent, air does not just swirl around, it is front to back only. You don't need an exhaust fan in a Torrent..

Ok, I’d forgotten how efficient this case was. It rated well years back when it was released eh?

 

So it appears the OP is using the case as it’s intended & has found the fan speed sweet spot?

https://au.pcpartpicker.com/b/Tw9G3C

 

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Posted
7 minutes ago, Ralfi said:

Ok, I’d forgotten how efficient this case was. It rated well years back when it was released eh?

 

So it appears the OP is using the case as it’s intended & has found the fan speed sweet spot?

I moved back into my Torrent Compact last night lol..

 

Neat trick with that case.. they say you cant fit a 140 in the rear exhaust, and normally they would be right. But you can literally snap a Thermalright TL or TY series fan back there no problem. So you can have 2x 180s, and 3x 140s in that tiny little box.

 

/ramble

AMD R9 9900X | Thermalright FW PRO, 3x TL-H12-X28, 3x TL-P12

Asus Strix X670E-F | 32GB Lexar Ares @ 6400 30-36-36-68 1.55v

Zotac 4070 Ti Trinity OC | WD SN850, SN850X, 3x SN770, 6TB

Asus PA602, 2x 200x38, 1x 140x28 | Seasonic Vertex GX-1000

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