Fan speed synchronisation

DennisJohnHarro · 12 Jan 2014 at 22:41

In my mini ITX build in the cm elite 120 advanced . I have 2 akasa piranhas which are quite quiet but at high rpm are very loud. My problem is that my CPU needs those fans to be on faster when gaming to keep it under 60C. I only have 1 fan header for case fans (4 pin). And to control the fans speed I need to use 4 pins. What I have done is put the fan that is closest to the CPU (blowing air across the heatsink) into the 4 pin and the other one (brings air in from the front) just coming from a molex to a 2 pin which then goes through a resistor to make it spin a bit slower. This would work however the fan that is controlled by the 4pin is controlled by the system temp not the CPU temp so it is not very effectice . is there any way to make the fan connected to the case 4pin be controlled by the CPU temp?

Sorry for the long winded question and if some of it doesn't make perfect sense to you

Bart_Hunt · 12 Jan 2014 at 23:03

Which motherboard is it?
I have Asus Z87i and in bios you can setup fan profiles.
I think that applies to all fans connected to motherboard.
Other than that, good solution is a fan controller - you can connect pwm fans to 3 pin controller as well and set them to same speed manually.
Also, I have Akasa Apache fans on my Prolimatech megahalems, running at 1000rpm and cooling my 4770k very well, temps max at 45 degrees. They run quiet at this speed.

DennisJohnHarro · 12 Jan 2014 at 23:09

Bart_Hunt said:
Which motherboard is it?
I have Asus Z87i and in bios you can setup fan profiles.
I think that applies to all fans connected to motherboard.
Other than that, good solution is a fan controller - you can connect pwm fans to 3 pin controller as well and set them to same speed manually.

Gigabyte GA-F2A88XN-WIFI I don't have the option to set up profiles I don't think. And I don't have 3 pins only 1 4pin. I have tried using a 4pin to 2x 3pin splitter that I had lying around. But this wouldn't let me control the speed.

Tealc · 13 Jan 2014 at 08:49

So do you want both fans at the same speed or different speeds?

It looks like you have two headers for fans, CPU_FAN is normally where the CPU fan is located. You could use a PWM splitter to enable a second or third fan to be controlled by CPU temperature. If you wish the case fan to be slower you'd either need a different PWM signal source, a fan controller or maybe that resistor in line with the case fan to slow it down a bit but still have some PWM response.

doyll · 13 Jan 2014 at 14:29

What Tealc said.

setter · 13 Jan 2014 at 14:35

PWM splitters work well, currently run 5 akasa piranhas from the cpu fan header. Could add another to the opt cpu fan header to run another 5.