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case fans question would this work?

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nut

Registered
Joined
Oct 24, 2002
I have a Lian-Li pc-60 and want to achieve lower case temps in hopes of lowering cpu temps. The fan on my heatsink is loud enough for me and if go with higher cfm fan it will be too loud for my tastes. My temps are not bad , but would like cooler.

I was thinking about changing my 80 mm in the back of my case which i think blows at 31 or 35 cfm's. Would i benefit by putting in a higher cfm fan back there while leaving the 2 front intake fans ( also 31 cfm's). I also have a top blowhole fan which also puts on 31 cfm's.

Would the higher cfm fan in the back offset any type of cooling circulation or disrupt any flow, in other words will it make it worse or have no benefit.
 

lazerin

Member
Joined
Jul 13, 2002
Location
Australia
I'm assuming that your blowhole is an exhaust? If so, by putting a higher cfm exhaust fan at the back will mean that you will be running negative airflow in your case (more air going out than in). I particularly like this setup because it lowers my temps considerably. However, some people prefer positive airflow (more air in than out) as it gives them better results. No one can tell you for sure, so my advice to you is to experiment. Find whats best for your system by experimenting and trying different setups etc

Good luck with it! :)
 

stool

Senior Member
Joined
Dec 20, 2000
Location
Albany, NY
One big drawback to negative airflow is dust accumulation. Dust tends to get sucked into your box in some unexpected places, like your CD and floppy, and between your slot covers. If you are somewhat meticulous about cleaning, and use fan filters, you can keep the problem under control.
 

Ross

Senior Intel-lectual
Joined
May 20, 2002
I have been dreading cutting up my Lian case for over 8 months. In fact, I have more than a few posts asking the same questions you are right now because I didn't want unnecessary holes all over the place.

The first thing I did a few weeks after I got it was to replace the 3 ADDA fans (~32CFM) with some Enermax adjustables. I removed the adjustable part so they ran full speed all the time (~40CFM) and are definitely not much, if any, louder than the ADDAs were.

It helped, but it was so long ago, I couldn't give you an exact number. Check around for posts from me back in the day :) I want to say it was 2-3C cooler switching to the 40CFM fans in the stock locations.

Fast forward to about a two weeks ago. I finally cut out a hole under the OEM rear exhaust fan location and placed the 4th 80mm Enermax fan that I had there as exhaust. Definitely no giant drop in case or CPU temps. That was definitely more negative than positive (in/out were equal + PSU out). At least I like to think the second exhaust is helping keep the vid card heat away from the proc :rolleyes:

About a week ago, I decided on replacing the intakes with 50CFM fans to get on the positive side. Then I got to thinking about finally dressing it up a little with some light and scoured everywhere looking for a decent looking LED fan that flowed 50CFM and wasn't any louder than ~35dB. They're just not out there yet, but the YS Techs would fit the bill nicely if you didn't want LED fans.

I let the aesthetic thing get the better of me and yesterday, I replaced the two 40CFM intake fans with some CoolerMaster 4-LED, 32CFM fans. I knew it was going to be a mistake in terms of cooling, but I just had to know what they would look like lit up behind the grill :) Case/CPU temps went up as expected.

After deciding that all of my case fans are quiet enough to not be a problem running more fans with fewer CFM each, I finally worked up the nerve to cut a hole in the side as an intake today to get back some of the intake CFM I lost with the LED fans. I placed one of the 40CFM Enermax fans in the side as an intake, a little towards the back and a tad lower than the HSF. OMG what a difference.

Even with the weaker intakes in front, the same HSF, same exhausts in the back, and same ambient temps for the last 2-3 weeks (21-22C), CPU temps are 2-3C lower *with the case closed* than they have been with the case open.

Back-to-back readings today @ 164FSB and 1.8Vc:
before the side intake, side open: 38C idle/43C load
before the side intake, side closed: 40C idle/45 load
after side intake, side closed (duh): 36C idle/40 load

All I can say is, I am kicking myself in the arse for not doing it sooner. No more listening to the loud HSF with the side wide open, I have my LED fans in front (I guess it's a plus :) ), and it's cooler to boot.

It worked so well, I just need to keep myself from installing a 2nd side intake under it and a top blowhole to balance it out. I want to at this point, but am afraid it can't any better and I'll just be adding fan noise.

BTW, HS+F = MCX4000/Tornado and this is as balanced in/out flow as it has ever been (104CFM in/~110 out including the PSU).

If I was going to do it again, based on what I've seen in my case, I would probably NOT add a second exhaust in the back under the stock one, but would add a 40-50CFM side intake over the HSF area and a 40-50CFM top blow hole to balance it out. Note that I haven't tried a top blow hole, but obviously the 2nd rear exhaust on it's own didn't do much...it's pretty much just balancing the CFM out of the case.