Just how important is positive case pressure?

[bk2005]

I have a Lian-Li 6075 case, that only has one intake fan on the the front infront of the hard drive bay, so its pretty obstructed with 2 hard drives in the cage. The other designed intake is just a "filtered" vent on the bottom, which I have an extra fan sucking air in. For exhaust, it has dual 80mm fans on the back, as well as the PSU, and a 80mm blow-hole. Here is a link to some pictures of it, here (http://www.performance-pcs.com/catalog/product_info.php?cPath=103_104&products_id=1053&osCsid=813b3bc8ca5e4f77de580451d56674e6), or here (http://www2.newegg.com/Product/Product.asp?Item=N82E16811112043).

So as of right now I have negative pressue, and I am buying the parts to go to water cooling. But the way I am thinking of setting it up it will be even worse on the negative pressure.

Right now I am planning on a dual 120mm radiator on the top, and an dual 80mm radiator on the current dual 80mm exhaust area. The plan is to use case air and pull it through each of these radiators, but I think that will make the negative pressure worse.

SO I guess the question is, is the negative presssure going to have a bad effect, and should I find a new way to mount everything? I want to keep it all internal, and with my hard drive cage, 3 optical drives, and a fan controller in my bays, there is no way for me to fit the dual 120 on the front and use it as an intake. Where would you suggest I put the two radiators, and should I pull air from outside or exhaust case air through them?

[millhouse]

its not possible to have negative or positive pressure in any case due to all of the holes in the case. fans will not change the pressure of the case. It is always even with pressure outside of case.

[ls7corvete]

If you have dual 120s on top they will be putting air into the case if setup right, pulling outside air in through the rad.

I would drop the dual 80mms though, not much more cooling and more restriction.

[lithker]

i have 2 120mm fans in the front as intake and not enough exaust 3 80mm (high pressure) i think. i tried putting in high cfm 80m and low cfm and it had no differense in temps. i dont think the fans can keep up with the intake.

if i were u i would put the 2 120mm fans in the top exausting and get rid of all the other case fans and seal the case air tight except the bottom intake by harddrive and bottom of case. i think this will get rid of the hot air collecting up top and at the same time draw in cold air from the bottom.

[bk2005]

Reason for two rads is for two loops. the dual 120 for the CPU, and the dual 80 for the video card, and northbridge. I know I could run one loop, but I like having a little fun :p

[rogerdugans]

Just how important is positive case pressure?

Very.
Not at all.
Depends who you ask.

There really is no simple answer to that question, unfortunately.
There are those who say that maxing the intake is best, others who prefer to max exhaust. It is fairly commonly agreed that running intake and exhaust fairly close together will USUALLY get the best results, but even this is not always true.

The only way to know what will work best for cooling a given system is to try different things.
If you do NOT experiment than you will never know for sure just what works best in YOUR system.

My own experience:
*For a quiet, mildly overclocked system I tend to go with more exhaust and use passive intake vents with no filters.
*For a maxed out, overclocked system I try to achieve a close balance with a hair more exhaust. Again no filters.
*If I was trying to achieve a system that needed little case housekeeping I would max intake, use filters and use passive vents for exhaust.

While most of the above was determined by messing about with aircooled systems, I have found that each lesson I learned with air cooling also works with water cooling airflow.

The most important thing, imAo:

To really get it right you have to mess around with your system and try different things. :)

[thorilan]

air cooling works the same way as water does.
flow>all

so however you can get the most flow with the least noise.