Ideal intake:outtake fan ratio?

[Floccinaucinihilipilificator]

Unfortunately, my motherboard only accommodates 4 fans, of which one slot is occupied by my CPU cooler (speaking of which, is there any way to combine multiple fans to share the same plug?). I have a Bitfenix Phenom M case, which has a vent in the front for the PSU, room for two 120 mm fans on the top, another 120 at the back, and either a 120, 200, or 230 mm at the bottom. Right now, I have two stock fans that came with the case at the top pulling air in, my PSU also pulling air in, and one slightly more expensive PWM 500-1800 RPM fan pushing air out the back. My bottom vent is open with no fan or parts mounted there, but the case comes with a cover if I need it.

Basically, I'm just wondering if it's okay to have more fans bringing air in than pushing out, (and what about more outtake than intake)? Thanks; this is my first build, and I'm no physics major, so I'm not quite sure if my airflow is exactly optimized.

Also of importance is that my top fans can't be reversed because I have a GPU with two fans drawing air from above it, where those fans are, so it would be pointless to have the top 120 mm's as outtakes (plus there's a dust cover at the top, so I think it's by design). I have about 4" of clearance behind and above my case.

Thanks!

 

[mi1ez]

I normally go with a negative pressure layout (more exhaust than intake), and am of the opinion if you can get rid of the hot air inside the case, cool air will replace it!

if you don't mind having no dynamic control of the fans, look for either molex fan or molex fan adapters. The fans obviously won't ramp up and down with internal temps but many come with resistor cables giving you a choice of 2/3 speeds.

Does your GPU exhaust out of your case, or in?

You say your PSU draws air in. I hope it exhausts said air and can be regarded is a separate loop as it were.

 

[Floccinaucinihilipilificator]

Okay, good to know. My GPU draws air in, but it sits below my top fans. Oh, I didn't realize the power supply isn't supposed to be part of the airflow. Would you recommend that I flip the top fans to be blowing out then? Hot air rises anyway. Or would that be bad for my GPU which wouldn't have as much access to cool air?

 

[mi1ez]

Depends on whether the GPU is exhausting hot air.

 

[Floccinaucinihilipilificator]

The GPU is drawing cool air towards it.

 

[mi1ez]

But what happens with the hot air afterwards?