case fans have no effect on cpu temp...?

I (finally) got all my case fans in along with a 3.5 fan controller. I have:
2 80mm intake fans up front
1 80mm intake on side panel (blowing right onto the HSF)
1 rear 80mm exhaust

I'm running the system in my sig. Here's the thing:

It barely makes a 1c difference by pumping all the fans on full blast. I can pretty much stay at 44c under load, or if I turn them all down it jumps to 45c.

This is all with my SI-97 and the Panaflo at full speed (since it cant reach to fan controller and the mobo NEEDS something plugged into the fan1 spot)

I figure I should benefit more from cool air coming in since my PSU has a big 120mm exhaust and my vga silencer is also throwing out some warm case air. Also I couldnt fit my IO backplate on, so its not like a tight seal or anything.

What's the deal?

Yeah, my case is kinda the same way. I have one 80mm front intake, 2 80mm side intakes (one over CPU/memory and one over PCI/AGP slots) and one 80mm exhaust with a passive vent on top and the 92mm fan in my PSU.
When I turn all the casefans up full blast, my cpu temp doesn't change much (a couple of *C). I like having the fans though because they are cooling the other components like memory, mobo chips (NB, SB, MOSFETS), and video card.

I think the only way a case fan is going to make much difference in CPU temp is if it were cconnected in a duct from the side of the case to the cpu HS/F. But even that probably won't make a huge difference.

You should try covering the fans up completely with a piece of paper of something instead of just turning them down to see what kind of a difference they really make...

Project86 said:

I (finally) got all my case fans in along with a 3.5 fan controller. I have:
2 80mm intake fans up front
1 80mm intake on side panel (blowing right onto the HSF)
1 rear 80mm exhaust

I'm running the system in my sig. Here's the thing:

It barely makes a 1c difference by pumping all the fans on full blast. I can pretty much stay at 44c under load, or if I turn them all down it jumps to 45c.

This is all with my SI-97 and the Panaflo at full speed (since it cant reach to fan controller and the mobo NEEDS something plugged into the fan1 spot)

I figure I should benefit more from cool air coming in since my PSU has a big 120mm exhaust and my vga silencer is also throwing out some warm case air. Also I couldnt fit my IO backplate on, so its not like a tight seal or anything.

What's the deal?

Click to expand...

Well, you're trying to push a lot of air out through 1 exhaust fan + PSU + vga silencer. The PSU is probably moving only a little air until it gets really hot, and the VGA silencer is probably pretty low-flow too. The net effect of all those intake fans is probably just to speed up your exhaust fans slightly. When you lower your intake fans, the overall airflow just gets more balanced, to where intake power = exhaust power. That might be why you see little difference.

Also, either way your HS is getting cool room air, so why would the HS care much? That single side intake onto the CPU HSF is probably doing most of your work keeping the intake air for your HSF cool.

The usual recommendation is to either balance intake and exhaust, or allow a lot of passive intake or passive exhaust, with all your fans on (respectively) exhaust or intake.

You might even try making that side intake passive, and turning all your fans to exhaust. But in that case a single intake 80mm wide might be too restrictive. But -- see what happens? I bet your CPU at least will be just as happy.

you must balance airflow...

IE Input fans equal to exhaust....

Fans generate heat themselves.

You are just blowing hot air IN without exhausting it.

The 120mm fan on the PSU is at a constant speed, I keep it on "high" since it's silent anyway.
I also keep the VGA silencer on high (2400rpm) for the same reason.

So I figure 3 fans in, 3 fans out. These are all quiet 20cfm or so fans, so it should be just about equal. And I don't believe they "generate heat", I don't feel any.

My adverage system temperature is 25 and CPU is 36 - 40 all I have is this.

Volcano 11 running at 3600rpm
1x Side intake fan (it's crap compared to my mates new 1 only blows a small amount of air in. Can't even set it's speed but it's directly over my 1GB Memory)
1x Exhaust fan (This is right next to the CPU fan no manual control again)
And finally 1x exhaust fan inside my case which is attached to my PSU so it puts out extra with the other exhaust fan at the back.

Also all my cables to my fans are tied back and since I have a SATA drive that thin cable is right at the bottom. I'm using 1x IDE round cable for my DVD-ROM drive and 1x ROUND floppy cable these again are all out the way of the side intake to improve cooling.

Not to mention my HDD fans too!

AngelfireUk83 said:

My adverage system temperature is 25 and CPU is 36 - 40 all I have is this.

Volcano 11 running at 3600rpm
1x Side intake fan (it's crap compared to my mates new 1 only blows a small amount of air in. Can't even set it's speed but it's directly over my 1GB Memory)
1x Exhaust fan (This is right next to the CPU fan no manual control again)
And finally 1x exhaust fan inside my case which is attached to my PSU so it puts out extra with the other exhaust fan at the back.

Also all my cables to my fans are tied back and since I have a SATA drive that thin cable is right at the bottom. I'm using 1x IDE round cable for my DVD-ROM drive and 1x ROUND floppy cable these again are all out the way of the side intake to improve cooling.

Not to mention my HDD fans too!

Click to expand...

Well, that's awesome...but not relevent to my post in any way. You are running (according to your sig) at stock speeds, so of course temps are low. But even then, the point was about how much the case fans are cooling (or not cooling in my case) the total system temp, which you failed to mention. But thanks for posting!

Another idea I'm having is that it's frickin cold at my house right now. I bet that might be helping somewhat-the entire metal case is chilly to the touch, so the heat probably has less of a chance to build up in there.

Project86: your CPU is breathing room air, not case air. (Isn't it?) Why would it show any difference no matter what you did to your case ventilation (within certain limits)?

Have you removed the fan grids from the case?

Is your HS's fan ducted to the side panel fan?

Wesson: Good point. We always talk X Y and Z about case fans, but the bottom line is that you can't get any cooler than the room air you started with. I suppose the real test will be running heavy load for a long long time (like an extended gaming session) and see if it is able to maintain these temps, which would mean air is being moved properly.

Yes, my fan holes that barely had enough holes to move maybe half fan's rated cfm have all been removed, so all fans flowing freely. No ducting yet for the side panel... I might consider it if I can find an easy way to do it. Don't wanna spend too much time on it at this point. Also, my side fan is 80mm and the HS fan is 92, which might complicate things...

Use one of those black plastic, flower pots...It will be bigger on one end and you can trim to length...The diameter can be adjusted also, with a cut along the length and staples...

Leftover containers work too..

um... your mobo doesnt NEED one plugged into the mobo header

in bios, just turn the fan warnings off, and restart it with it unplugged


and the wire length problem, just bust out the soldering gun and extend the wires to your fan controller


that'll help the most, because the mobo fan header ususally adjusts fan speed to what the mobo thinks is the optimal fan speed to keep the CPU at a half-assed temperature

Flower pot eh? Interesting idea...

As for the fan header, yes my mobo DOES require it. I don't have any options about it in BIOS, and it simply will not boot without something plugged in.

Also, I have never heard of a mobo adjusting the fan speed... I know for a fact mine doesn't.