Sonata and CPU fan direction

cwl999 · Post by **cwl999** » Fri Jun 20, 2003 12:30 am

I know that the normal direction for the CPU fan to blow is towards the CPU.

But for those owners of the Sonata will already know, the 120mm exhaust fan is directly in front of the CPU fan (obviously at a right angle).

Therefore, wouldn't having the CPU fan suck air from the CPU cool the case (and possibly the CPU) better since the hot air leaves almost immediately instead of being blown around the case.

ghowarth · Post by **ghowarth** » Fri Jun 20, 2003 3:31 am

Yeah - try it out, it's an easy enough test

Mine makes a difference of 2-3 degrees. It does mean that the chipset close to the cpu doesn't benefit from the fan's exhaust airflow, but in practice this this is no biggie if your case fans provide airflow over the board.

cwl999 · Post by **cwl999** » Fri Jun 20, 2003 3:44 am

Agreed, I have been thinking about the other passive heatsinks that may be cooled by the air from the CPU.

I've got an Abit NF7-S mobo modded with a Zalman passive NB32J (sic) heatsink. I don't think there will be much problems with the NB even though the FSB is at 215.

I'm more worried about my 9500pro modded with a HP-80A (sic).

The air coming out of the Sonata exhaust is always cool (compared to the PSU). This is probably due to the "Antec" holes on the side panel. I s'pect if I block the holes, the air flow will be much better because the air has to now come of the front air vents, therefore more air passing thru the various heatsinks.

Will have some fun over the weekend and post conclusions.

Post by **Ralf Hutter** » Fri Jun 20, 2003 5:11 am

cwl999 wrote:
Will have some fun over the weekend and post conclusions.

That's the best way to learn too. It's hard to beat "hands-on" experience for learning.

dago · Post by **dago** » Fri Jun 20, 2003 6:01 am

One of my other idea for the sonata would be to completely separate the psu part from the Mboard, in order to have a tunnel going from fron top 5 1/4 bays (I don't use them), then a 92mm fan, then the PSU (no fan, no grills).

Don't know if you see ?

then, play with direction of the last 3 fans (2 120 Case + 92 CPU) to get the better temp.

I'd like to do that on w-e (and in fact, for many w-e), but with this weather, staying at home is the last thing I wanna do

cwl999 · Post by **cwl999** » Sat Jun 21, 2003 6:16 am

Well looking at the results, I can only say that it doesn't make much difference which direction the CPU fan is blowing. I'm keeping mines the normal blowing towards the CPU direction.

Code: Select all

                mobo    idle            load
normal          28.0    37.0    33.0    44.0
l               31      40      35      45.5
l+r + cpu       31      41      36      46.5
l+r             31      40      36      46

Whilst looking inside the case, it's clear that a lot of air enters the case via the "antec" holes. You can clearly see "antec" in dust both on the entry points and the imediate surface behind the holes (my PSU and cdrom)

I've covered these up now. I would expect an increase in PSU temp and therefore an increase in PSU fan speed, which I believe I noticed but not recorded.

energy · Post by **energy** » Sat Jun 21, 2003 1:34 pm

One of my other idea for the sonata would be to completely separate the psu part from the Mboard, in order to have a tunnel going from fron top 5 1/4 bays (I don't use them), then a 92mm fan, then the PSU (no fan, no grills).

I did this on my Sonata using a couple of sheets of acetate material (plastic paper used for overhead projectors), and allowed the PSU to pull air in from the ANTEC holes on the sides. Big difference to Zalman PSU noise level. My next step was fitting a 15dB NMB fan externally to the PSU, and plonking the entire PSU on top of my case on a piece of foam so that it can get all the fresh air it likes. Silence.

ghowarth · Post by **ghowarth** » Sat Jun 21, 2003 6:19 pm

bet it looks a bit silly stuck up there, though

oogabooga · Post by **oogabooga** » Sun Jun 22, 2003 2:37 am

no no - my modified enermax (thanks MikeC!), has a lovely home on top of my case - and I can put it upside-down which helps convection - also removes a heat source from right by my CPU...

It may look geeky, but when everyone already knows i'm a geek, i don't care

cwl999 · Post by **cwl999** » Sun Jun 22, 2003 11:23 pm

Having left my system on for a few days with the "antec" holes covered, the overall temp has risen by 2-3 degrees, the PSU fan has also increased in speed by ~1000 revs and obviously extra noise with it.

Time to look into a panaflo L1A to replace my PSU.

lenny · Post by **lenny** » Mon Jun 23, 2003 1:10 am

Did you try the holes covered experiment with the CPU fan blowing away from the CPU, or towards it?

I know your initial experiment shows little difference, but with less ventilation (holes covered) it may help more.

Maybe some kind of shroud around the 120mm to trap more of the CPU exhaust will help?

It should also be interesting to watch the airflow visually. Can anyone suggest a good way of doing this? The folks at Tom's Hardware did it with cigarette smoke, but that's hardly good for the components.

cwl999 · Post by **cwl999** » Mon Jun 23, 2003 2:38 am

Yes, I tried that combination as well. Overall, the fan direction had little perceivable affect on the core temp.

I do know that the mobo temp is higher with the holes covered, this is probably due to the extra heat that is gained whilst travelling from the front to the CPU.

marc999 · Post by **marc999** » Mon Jun 23, 2003 12:41 pm

My D8000 has the same problem (the 120mm fan right by the CPU HSF). I have a Coolcases modded one, so the fans are mounted by regular wood screws into rubber grommets. Anyway, it occured to me that I could probably mount the 120mm fan on the back outside the case, instead of inside the case. To get power to the fan, run the fan cable up to the bottom of the PSU slot. Cover the cable of the fan that the PSU sits on with electrical tape just to make sure. This only saves you 25 or 38mm, depending on the thickness of your fan, but it may make a difference !!