Question: Total cfm In/Out of case?

[KyleGagnet]

Basically is it better to have more fans blowing into the case that out of the case or vice versa? When I first thought about it I thought you would want more going in... that way, the only air going into your case is coming from where you want it (your fans)... If you have more exhaust, then it sucks air in from different places. I could be totally wrong on this, that's why I'm asking...

 

[dunkster]

What counts is air-flow THROUGH the case. How you get there is highly dependent on the design of the case and fan efficiency.

When I first got my Antec 1030, I played with combinations up to 2 80mm front intake + 2 80mm rear exhaust. Best overall efficiency was with the 2 rear exhaust fans. The front intake fans were pretty ineffective, so I removed them to lower case noise and lower PS loading. The placement of the rear exhaust fans produced good airflow and a short-path rear exhaust of hot air from the cpu cooler.

Different solutions for different cases.

Since most of us don't have flowmeters, the best available gauges for case ventilation efficiency are probably system/board temp and cpu-idle temps. Of course the outside of the case should feel cool to the touch.

Hope this helps!

 

[PCHPlayer]

I think you will get many differing opinions on this topic. I agree with Dunkster that the most important factor is the exchange of hot air for room temperature air. Many other factors come into play though. You can wind up with hot air pockets depending on the flow of air, but without some kind of air flow detection equipment you would never know (except if a temperature gets really high).
Dust is another factor. Personally I don't see any need for intake fans unless you are trying to control dust. The air will get into the case through any available opening. After all when was the last time you heard of a case imploding? I have an Antec 1040 with 3 exhaust fans (including the power supply fan) and 1 intake fan. I have a filter in front of the intake fan that traps a crap-load of dust.
Bottom line: If you case temperature is close to room temperature (within 5 C, 9 F) your doing just fine.

 

[dolph]

dust is usually an issue. if you have more intake fans then outtake fans, then you have positive pressure inside, thus forcing out dust that could sneak in through cracks in the case (no case is airtight!). so 2 in/1 out, or 3 in/2 out would be the way to go.

 

[SuperPickle]

All of the above advise is pretty sound. The only thing I'd like to add, is that pressure, both positive and negative decrease the overall efficiency of the fans possibly creating more noise. Air in=air out is optimum efficiency (barring that whole dust-issue).

 

[Jhhnn]

Without filters, dust gets in, settles out wherever it wants, slight pressure differentials inside vs out are a non-issue. Filters help, and are most effective in a slight positive pressure scenario. That's easier said than done- current computer case design is, uh, lousy in this respect.

I'm with Dunkster about exhaust fans, they seem to work best in a wide variety of scenarios, provided that they're well-placed. Heat is the active force, removing the warmest air from the case most effectively prevents temp equalization inside the box. Moving the fans further away from your ears also helps with perceived noise levels....

 

[jiffylube1024]

Yeah like other people stated, you want to have your case set up so that you have a single direction of airflow in the case. An example would be intake fan(s) on the front of the case and then exhaust fans in the back, with a couple of fans in the middle to buffer air along towards the back. This wasy there's always fresh, cooler air flowing over the CPU/Mobo/etc ...