pushpull Push Pull Different CFMs

[Astro16]

Is there a diminishing return if I put 2 fans with different CFMs? Let's say a hyper 212x, I'll use a frostflow (if that's what the stock fan is called) as push and a 2200rpm rated fan as pull will lower CFM then place them vice versa. Or should 2 fans match each other's CFM? And one more thing should the exhaust fan at the rear side of the case needs to be faster to dissipate the heat out of the case? I noticed most fans that come with cases have slower rpms.

[unidentical]

Won't matter. For case you should always have more filtered cfm than exhaust to prevent dust. 

[failblox]

Honestly I don't think it matters too much, but I would place the one with the higher CFM at the front/intake of a cooler such as the Hyper 212X.

 

Generally, you want to have positive air pressure inside your case, which means that you have more intakes than exhausts for fans. This ensures that the pressure inside your case is higher than the outside air pressure so that air will be pushed out gaps instead of sucked in (which is what would happen is you have negative air pressure - more exhausts than intakes). As long as the number of intakes and exhausts is around the same, the RPM shouldn't matter as long as it's moving enough air through the case.

[WoodenMarker]

It depends on how much cooling you need and what fan speeds you're running. With higher fan speeds, it easier to run into diminishing returns. 

At lower speeds, more fans help make up for airflow while keeping noise lower. 

[Astro16]

Thanks for your inputs, so in a tower cooler it would theoretically be better if I place a higher CFM fan at the front/intake then the lower CFM one as exhaust?

Makes sense, in that scenario, how should I set the rpms then? which one should be faster? Is it safe to assume the back/exhaust fan should be faster?

[WoodenMarker]

42 minutes ago, Astro16 said:

Thanks for your inputs, so in a tower cooler it would theoretically be better if I place a higher CFM fan at the front/intake then the lower CFM one as exhaust?
Makes sense, in that scenario, how should I set the rpms then? which one should be faster? Is it safe to assume the back/exhaust fan should be faster?

There's no point in intentionally using a fan with less CFM. If there's a better fan, just use the better one.

 

You need to quote a post or tag a member or else they won't get a notification you replied to them.

[Astro16]

2 hours ago, WoodenMarker said:

There's no point in intentionally using a fan with less CFM. If there's a better fan, just use the better one.

 

You need to quote a post or tag a member or else they won't get a notification you replied to them.

oh okay. just new here. thanks.

well, I only have 1 spare fan which has a lower cfm but higher rpm. plus the one I have on my 212x, since it came with an extra bracket I asked. Wanted consult first before putting the other fan on the sync as an additional fan.

[WoodenMarker]

Just now, Astro16 said:

oh okay. just new here. thanks.
well, I only have 1 spare fan which has a lower cfm but higher rpm. plus the one I have on my 212x, since it came with an extra bracket I asked. Wanted consult first before putting the other fan on the sync as an additional fan.

It's hard to tell without testing it and it might make very little difference if there's a fan right behind that at the rear of the case. 

Just try it out and see for yourself.