PC Thermals: 0 v 1 Rear v 1 Top-Rear v 2 Exhaust Fans

[Ralfi]

Hey there, back again with more testing (following on from here, here & here), this time comparing system temps above ambient (C°), with variations of typical exhaust fan setups, in an airflow-focussed case (ie. mesh front);

 

Here are the 4 exhaust fan orientations:

(Note: Top-Front fan’s disabled)

 

Zero Exhaust Fans...                       1 x Top-Rear Exhaust Fan...           

          
1 x Rear Exhaust Fan...                   1 Top-Rear + 1 Rear Exhaust Fans...

     

 

After running the FurMark GPU & CPU stress-tests for 30 minutes, here are the results...

 

     

 

CPU

The temps were very similar with any number of exhaust fans, but you can see how much harder the CPU fan needs to work with 0 exhaust fans; ~250RPM more than with 1 exhaust fan, & over 300RPM more than with 2 exhaust fans.

 

Depending on your fans, you may or may not notice the extra noise created by the increased RPM. My noise levels remained constant with all these tests fyi (37dB).

 

GPU

Temps were similar with 0 or 1 exhaust fan, but with the CPU fan not needing to spin as fast to maintain the temp with 1 exhaust fan. When using 2 exhaust fans, temps dropped about 2° via less fan RPM.

 

GPU Hotspot

No real change in temps here. Only a reduced fan RPM.

 

Motherboard Temps

Similar temps recorded across the board. VRM MOS seemed to benefit most from having 2 x exhaust fans, interestingly nearly 3° cooler than with only 1 x Top-Rear exhaust & 2° cooler than with only 1 x Rear exhaust. This was with both exhaust fans spinning at 100RPM less than with a 1 exhaust fan setup.

 

Overall, system temps averages above ambient weren't too dissimilar. Less than a degree across the Motherboard & the whole system, but the fan RPM efficiency continues to tell a bit of a story as to why more exhaust fans help, especially when you want a quieter system.

 

Also, there was no difference between having 1 Rear & 1 Top-Rear exhaust fan. Fan RPMs & temps were basically identical.

 

You may hit diminishing returns the more exhaust fans you add, but for most airflow-friendly setups, if your case allows, 1 x Rear & 1 x Top-Rear of efficient, static pressure fans should be sufficient. Match them with 3 front intakes, & you've got yourself a positive-pressure case which will get the job done*.

 

*For a typically medium power-demanding system, similar to the below:

5600x

6700XT

16GB DDR4 RAM

2 x M.2 NVMe SSDs

[Joman]

Thanks for doing this test and recording the details. My cougar Duoface Pro RGB comes with 3 120mm intake and 1 120mm exhaust at the back, my PSU is in intake configuration (fan side down). I was wondering should I add 1 more exhaust fan. I think i will buy the 140mm one for the rear and move the 120mm to the top. No temp issue but I always go for lower PC temp

[Ralfi]

9 hours ago, Joman said:

Thanks for doing this test and recording the details. My cougar Duoface Pro RGB comes with 3 120mm intake and 1 120mm exhaust at the back, my PSU is in intake configuration (fan side down). I was wondering should I add 1 more exhaust fan. I think i will buy the 140mm one for the rear and move the 120mm to the top. No temp issue but I always go for lower PC temp

Hey there. Puts a smile on my face that this helped you  

 

If you modify your setup with two exhausts, it should reduce temps slightly but also reduce the RPM of your fans & hence noise of your PC (you'll notice this more, depending on your fans).

 

Let me know how it goes.

[RevGAM]

On 11/18/2023 at 6:43 AM, Ralfi said:

Hey there. Puts a smile on my face that this helped you  

 

If you modify your setup with two exhausts, it should reduce temps slightly but also reduce the RPM of your fans & hence noise of your PC (you'll notice this more, depending on your fans).

 

Let me know how it goes.

Nice job. I also do fan testing and suspected what you confirmed, so that is helpful!