Having an 80x10 mm fan or a 92x14mm fan at the top of the case appears to make no noticeable difference to the measured CPU and GPU temperatures. Do not have the facility to measure mobo temps or any other temps as I am only using afterburner and have a basic mobo.



Method

- EVGA 1070 SC, H97I Plus, i5 4750, Intel Stock Cooler, stock bios settings, fan profile "standard" (which is 20% CPU at 30deg, 100% cpu at 70%), Corsair SF450

A) Preheat - Had the system running Prime95 and furmark at the same time, was pre-heated for about 60 minutes prior so the whole system was warm and had observed temperatures stabilised for at least 10-15 minutes

[ambient 23 deg, CPU

B) Testing - all tests were given 10+ minutes of running after temperature stabilisation to ensure equilibrium temps are reached.



1) 80x10mm at silent RPM - I had started with the 80mm fan taped to the chassis over the PSU. No mods needed. Had it running at a quiet voltage (same noise level as GPU loaded) (around 5v for my fan). No measurable difference



2) 80x10mm at full 2100 rpm at 12V. - Also no significant difference to GPU or CPU temps. Feeling the chassis for changes in airflow, no noticeable difference. The GPU is still pushing air out the top and bottom very well, and hot air exhaust from the GPU still overflows into the CPU side and hot air comes out of the side panel under the PSU. Fan is very noticeable at this point, more than doubling the noise of the system to my ears.



3) PSU moved down 10mm with spacers, 80x10mm at full RPM. - PSU was not screwed into the case, but it was still a tight fit wedged against the Mobo and with my cables firmly tied together. Ran this test with the 80x10 at full RPM again, and no difference in temps too. Anecdotally the airflow from this fan is less "suffocated" by its proximity to the PSU and the structural fin of the PSU bracket, so it feels like there is more airflow and less noise.



4) With PSU down, 80x10 turned off, and no difference in temps noted.



5) Noctua 92x14 fan installed, PSU down 10mm, run at full RPM, also no significant difference in temps noted. feels like there is more airflow from this fan, but its proximity to the PSU plug (only 2mm of space between blades and psu plug) causes a bit more interference noise. Air temperature from this front fan is much cooler than the air from the back end of the case where the GPU blows the air out directly. Airflow rate is not significantly higher due to the top fan, compared to what the GPU pushes out itself. Noctua is just as loud as the 80mm, lower frequency tone though.



6) PSU down 10mm, no front/top fan installed. Also no significant difference in temps.



7) 80x10mm fan over the back area, over the PCIe riser. at full RPM. There is some interference noise from the proximity of the riser (1mm) but airflow is not noticeably more than without the fan, and no measurable differences in temperature.





Data Summary

- The addition of a fan within the top of the case provided no measurable benefits to CPU and GPU temperatures.



Discussion

- There was an expectation that the fan would help suck air out and assist in the removal of hot air, allowing for better case temperatures and hopefully GPU and CPU temps.

- My measurements of temperature did not allow me to really measure other areas in the case, so there might have been some benefit, but from the feel of the case and where the hotspots areas, such as the side panel area under the PSU on the mobo side where hot GPU air also exhausts, there was no noticeable difference in temperature, suggesting that the small slim fan simply does not provide enough airflow to negate the amount of hot air being pumped into the case.

- Secondly, the GPU has vertically orientated fins, and naturally has vertically directed exhaust air that moves with a rather well projected direction. Airflow from the GPU when bench mounted can be felt a good 30 cm away from the GPU in a fairly 'tight' column of air. Compared to my earlier Asus 670 which had fins horizontally, the Asus would have hot air projected out the ends of the card, but along the length of the card, exhaust air did not have anywhere near the same velocity as the vertically oriented fins of the EVGA cooler. This means that the EVGA naturally has more exhaust velocity that suits the DanA4 and already drives a good amount of hot air out of the case, and that the slim fan is only able to match or at best slightly improve exhaust air, but not make a significant difference.



- There is still a significant amount of hot air dumped into the case as the GPU is clearly creating positive pressure and there is no significant exhaust opportunity that can negate the positive pressure generated by the GPU, and therefore naturally hot air is pushed into the CPU side. I was hoping the top fan could reduce this, but clearly it did not make any significant difference.



Conclusion

- The slim fans 80x10 and 92x14 mounted within the top area both over the PSU and PCIe riser made no differences to the CPU and GPU temps, and had no perceivable impact on the positive pressure within the case generated by the GPU.

- They did however make the most noise in the whole system, much louder than the GPU itself. System noise at full GPU and PSU load was more than doubled simply by the use of these fans at full rpm.