2 Fans on top of each other....

I have two 120mm fans. If I put this on top of each other will it create better air flow or just disprut air flow?

Reason Im asking is because I got a new motherboard that supports PWM fans (System controlled). I got a liquid cooling system where I have a 120mm PWM fan connected to the raidator. Now the fan with system control is running a 650 RPM (really slow) and the water is 40 - 42C and the CPU is at around 57C. I have a spare normal 120mm fan where I can control the speed with a nobe. If I hook this 120mm fan and put the PWM 120mm fan on top. Will it mess the airflow up?

Hope it makes since

--------+-------|
FAN | FAN | RADIATOR HERE
A | B | --->> Air flow
| |
| |
| |
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Basically I want fan A to run at 1300 RPM constant and if needed temps get to high have the system control fan B to whatever needed

Pretty sure that's a good way to burn up your fans but I can't give you specifics on it so don't quote me on it. I've always heard that its a very bad thing to try....

Ok, thats why i asked

Your motherboard isn't controlling the fan properly, this happened to me when I upgraded my heatsink, the stock fan was a 60mm, and I put a 80mm in the same 3 pin, and the fan ran about 500RPM. What you can do is hook it up through the 4 pin on your power supply, this should max out the speed of the fan, and get everything nice and cool.

I think the reason stacking fans isnt good has something to do with them creating a bubble of low pressure inbetween, and that hurts the fan. But in any case, stacking them = bad.

Yeah, its a pressure thing. besides that, you aren't going to be able to move any more air anyway. The fans have a max RPM and the CFM of air that flows is directly proportional to the fan RPM.

Quote:

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Originally Posted by Frogon

Your motherboard isn't controlling the fan properly, this happened to me when I upgraded my heatsink, the stock fan was a 60mm, and I put a 80mm in the same 3 pin, and the fan ran about 500RPM. What you can do is hook it up through the 4 pin on your power supply, this should max out the speed of the fan, and get everything nice and cool.

I think the reason stacking fans isnt good has something to do with them creating a bubble of low pressure inbetween, and that hurts the fan. But in any case, stacking them = bad.

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No it is controlling properly. Its just that if the CPU temp is cooler than 59C it'll run the Radiator fan at 560 RPM. At this speed the water temp gets to about 40C while the CPU is at 58-59C. Once I do something that makes the CPU usuage go up to like 100% or whatever the CPU temp will jump to about 60-64C. Once its that hot the motherboard will spin the CPU fan at about 1900RPM until the temp gets cooler. Each degree the CPU gets cooler the slower the fan will spin.

The thing is when I had my old fan where I controlled the fan speed by a nobe I always had the fan run minimum at 1300RPM. It was rather quiet and the temp was alot better. The CPU was at 52C and the water is about 33C or so. Now I checked in the BIOS and read Intels website and everything. Intel says that DONT allow any kind of software to control the fan speed because of Virus attacks; its all done by the system.

But all I want to do is get the minimum fan speed to 1300RPM instead of the 560RPM. And since I cannot do it in the bios or via software I figured that I could simply could stack the fans that way I have one that runs at a constant 1300RPM and the other at 560 RPM. So that once it needs better cooling just have the 560 RPM fan do whatever it needs to do.