My CPU Duct (Pictures!)

ricktwig · Post by **ricktwig** » Fri Jun 18, 2004 7:17 am

Wow! Sexy mod. (Is it weird I'm turned on by this?) Looks like HAL-9000, but in blue.

OK. I happened on this because I am considering doing this, but for different reasons...

1) Counter-current cooling. http://www.silentpcreview.com/article160-page2.html I would like to see if using a duct instead of the glove cuff will encourage counter-current cooling.

2) CPU cooling with external (cooler) air.

Some thoughts...

I want to extended the tube down past the horizontal fin sections on the Zalman, and keep it "tight". I found an acrylic supplier that sells a tube by the foot that will leave about a quarter inch gap all around. I will block this with some type of anti-vibe foam that can handle touching the heat-sink. Hopefully, the tight tubing would encourage counter-current cooling by not allowing the air to escape through the top of the fins. (I might even consider using both the duct *and* a glove cuff.)

Blowing vs venting at the CPU duct. I've seen some discussion about which would be better. [disclamer: I'm not a physicist, but I did stay at a Holiday-Inn Express last week.] Since the hottest part of your computer is the CPU, I would think that cooling it with outside air would gain the most benefit. Also, since I like using the ASUS A7N8X, the inbound air should cool the FSB passive heatsink nicely.

As far as case cooling, I'm not going to over-engineer here. I'm going to keep a matched number of fans (1 in / 1 out). I might possibly add a little more inbound to get positive pressure. I've heard that can cut down on injested dust, and with a clear case, that would be nice. Here's what I'm thinking...

Inbound: Duct over Zalman. I'm going to put another 120mm fan "in series" on the CPU duct. (I don't want the Zalman overworked as both a CPU fan and a case fan.) So, you'd have...

case wall -> 120mm fan -> duct -> Zalman flower

Outbound: Some type of quiet PSU (but not fanless.)

Inbound 2: 120mm fan under the harddrive area. This would be instead of the normal fan on the front of the case, blowing in on the harddrives. I'm thinking case feet can hold the fan off the floor, and the carpeting will help reduce some of the fan noise.

Outbound 2: Blow-hole fan. Some type of quiet 120mm or 92mm. Since it will be on top, it might be the worst place for noise escape.

The placement of these ins/outs I'm hoping will encourage good back-to-front and top-to-bottom case air movement.

Oh, also, in the spirit of quiet, I'll probably use the Arctic-cooling VGA silencer. This also vents outside the case.

I'm hoping since I'm going to use 120mms I can run them @ 5V. Is bigger always better?

[So, start the rock throwing! Taking all comers!]

fancontrol · Post by **fancontrol** » Fri Jun 18, 2004 8:47 am

dasman wrote:Nope, I hadn't seen that -- but the text in that first link is a little confusing and appears to suggest that the CPU can be cooled passively!

The PDF says that CPU HS fans are still required. That's probably related to their requirement(?) that the duct be seperated from the CPU by 1/2" or more. I had a duct that fit snugly over the fan and HS and ended up not needing the fan at all.

In the mechanical drawings--also in the PDF--they have deformed the duct grille upward. That certainly adds cost, anyone have an idea of the benefit? It would only make sense to me if there was a fan in close proximity to the grille.

sammermpc · Post by **sammermpc** » Fri Jun 18, 2004 2:18 pm

I apologize if this is common knowledge, but I am new at the "hack away at your case" game. What tools do you use to cut through aluminum.steel and clip away at the everything?

I have that very pencil cup (though i use it for pencils) and it seems pretty solidly constructed.

tay · Post by **tay** » Fri Jun 18, 2004 2:40 pm

Check this sticky thread in the cases and damping forum of this site. The best guide i've read. If you search for Wiss tin snips you'll get tons of other threads that you might want to browse through.

http://forums.silentpcreview.com/viewto ... +tin+snips

Tools popularly used are
Wiss tin snips
nibblers
dremel tools

happy modding and welcome to spcr!

Bistro · Post by **Bistro** » Fri Jun 18, 2004 7:54 pm

I just finished this mod this evening and am happy to report some excellent results with it. Mucho thanks to josephclemente!

The system:
Asus P4C800-E deluxe mobo
Antec P-160 case
Rear 120mm Enermax fan on High
P4 3.0ghz with Zalman 7000 Al-Cu HSF
Thermaltake Silent Power 480W psu
NO front fan--just a filtered intake grill

I hear no significant increase in sound at all. Had the Zalman fan on High setting. "Idle" temps were taken after letting the system sit for 1/2 hour between temp recordings. To determine CPU load temps, I used Sisoft Sandra's CPU Multimedia benchmark test. Used Asus Probe program to record temps.

No duct:

CPU @ 3.0ghz (Pentium 4)---Idle: 95 F, Load: 107 F
Motherboard---86 to 87 F for both

CPU Overclocked to 3.6ghz --- Idle: 100 F, Load: 113 F
Motherboard--- 87 F for both

With duct:

CPU @ 3.0ghz --- Idle: 89 F, Load: 100 F
Motherboard: 78 F for both

CPU overclocked to 3.6ghz --- Idle: 95 F, Load: 105 F
Motherboard: 82 F for both

A not-too-shabby reduction in temps...especially with the overclock.

sammermpc · Post by **sammermpc** » Sun Jun 20, 2004 12:31 pm

I just wanted to say that I too have completed this mod. Bsaically did exactly as Joseph did, without the cool LED's (how do you do those btw?). Cut a metal funnel which just reaches the edge of the heatsink, and used the same mesh pencil cup. I have not broken 40c even after a few hours of prime95 stress testing! Thanks so much.

My average temps are not so great. mid 30's, but at times, get this - my cpu temps will dip under my case temps. Pretty neat, even at full load case to cpu differential doesn't top 4c. If I can figure out my camera and comp I'll post some pics. I love nibblers now, heheh. Pretty good for 4.99 at radioshack.

Bistro · Post by **Bistro** » Sun Jun 20, 2004 5:48 pm

sammermpc wrote:I just wanted to say that I too have completed this mod. Bsaically did exactly as Joseph did, without the cool LED's (how do you do those btw?).

I just took a blue Lazer LED and connected it with some duct tape to the bottom of the rail that the psu sits on. Shines down onto the duct. Real nice effect.