Ideal Speed Differential (If Any) For Push-Pull Fan Configuration

[VideoSavant]

I have a push-pull configuration for my EVO 212 Plus and my motherboard allows me to set speed profiles for each of the CPU and CPU_Opt fans.

So, I'm wondering what is the optimal approach in terms of the fan speed differentials? While I understand the value of varying the speed of the fans according to CPU load, I'm curious about whether there is any benefit in having a differential between the two fan speeds at any given level, and if so, which should be spinning faster (push or pull), and by how much?

Or is the best approach that the speed be uniform for both fans as the speed increases across the workload curve?

I searched here (and Google) to see if this question had not been asked and answered previously, but surprisingly found nothing. But my apologies if this is an old question.

 

[DasHotShot]

Ideally you want cool air to enter the case and hot air leaving the case at a similar rate, creating "airflow".

If one is set to a higher rate than the other you might not achieve the best results.

My suggestion would be to test out a couple of settings, monitoring all your component's temperatures to determine if one does work better than the others.

 

[faalin]

Having two different speeds on your fans for the evo 212 wont do much, maybe a slight strain on the fast of the two fans . If the front fan (push) is going faster then the rear fan (pull) it will push the air through the other fan speeding it up. The same goes the other way around, the rear (pull) is going faster it will pull air through the front slower (push) fan speeding it up.

 

[DasHotShot]

With a radiator wedged in between I don't think the fans will affect each other this much. I believe it is more important to focus on heat dissipation

 

[VideoSavant]

OK, thanks for the suggestions so far.

I've lined up my cooler fan settings to be as identical as I can get them, and it appears that the airflow created by the push fan is providing additional energy to the pull fan.

For example, at 20% workload, the push fan is spinning at 579 rpm and the pull fan is moving at 683; at 80%, the push is 1885 rpm and the pull at 1985, A bit unexpected after those two sets of data, at 100%, the push spins at 2213 and the pull is a bit slower, at 2170.

There's no problem with my CPU temps. At idle, I'm in the mid 30Cs and the highest I've seen since completing my build is low 50s. I've not attempted any overclocking yet, but nothing I've seen relating to performance or running temps has me concerned. I'm not even sure I need to overclock (though it might be fun).

The reason for my question is that I've never done a push-pull configuration (this is just my second build) and I was curious if there was any standard for this sort of thing. I'm not an engineer (my credentials are more along the lines of a science fair participation trophy), but it seems like there would be a benefit to moving the fans at the same speed. It seems like that would create a more consistent, directed stream of air, rather than something more variable.

Or maybe the increase in pull fan speed has some benefit I haven't thought through.

 

[DasHotShot]

It's probably best to keep them as identical as possible to create that steady stream. The only thing I can think of in terms of benefits of having a high pull is that heat is sucked away from the heatsinks more quickly however you want to provide it with enough cool air to ensure the temp remains as low as possible.

The temps you mention are basically perfect for air cooling. I use a closed loop water cooling solution and don't achieve such good thermal readings...I have OCed and Overvolted though, so expect an impact once you do.