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Parallel fans on the sp-94 make cool & quiet @3.84ghz.

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orion456

Member
Joined
May 31, 2004
Having read a ton of great posts I came to three conclusions. The sp-94 with AS5 is an awesome heat guzzler. The dead spot significantly affects cooling. And blowing hot air from the hot heatsink onto a motherboard isn't a great idea.

As a result, I decided to use a 4" duct (dryer vent from the local hardware store) over the heat sink and the fan sucking heat from the sp-94 and blowing it directly out of the case. This means I don't have to have lots of auxiliary fans blowing air in and out. I have two 80mm panaflo fans on medium speed blowing on my hard disks and the two back fan openings are open to allow air to flow in as needed.

I used a spreadsheet analysis of airflow in the sp-94 heatsink to see clearly that blowing air in the usual way with one fan causes the air from the edge of the fan to be sucked inwards at high velocity carrying heat INTO the sink. The inward sucking is caused by the vacuum that forms under the fan hub. The harder you blow on to the edge of the sink, the greater the vacuum under the hub and the more air that heads towards the center. In essence hot air from the outer fins is being sucked back into the center of the heat sink making it harder for that air to cool the dead spot area. Therefore at least some of the heat transported by the evaporation tubes to the edge is being returned to the center area. Analysis shows that upon exit from the heat sink the air flow is pointing downwards towards the mother board, thereby heating the board. There is also a significant level of churning where high speed hot air from the edge is recycled back into the fan, again reducing the cooling effect.

To eliminate the dead spot, I attached two 92mm panaflo fans side-by-side and put the high speed center of those two fans directly over the center of the sp-94. Maximum air flow occurs at the center of the heat sink, instead of a minimum flow. The spread sheet analysis showed that the air flows quickly from the center and pushes on the slower speed air near the hubs which are now located outside the heat sink. (See my pics for a drawing of the air flow for one fan [on the left] and two fans [on the right] the length of the drawn line represents the speed of the air at that point. See how the air flow for one fan is actually towards the heat sink at high velocity for almost half the depth of the sp-94 and the exit air is slow from the center.) The reverse flow takes place if the fans are reversed.

Results: p4 3.2c overclocked to 3.6 ghz, pc3700 memory

With the standard intel fan and heatsink (which had a built in 3" duct to suck air in over the heatsink) my load temps were 58c CPU and 48c mobo, idle 38c and 42c (80mm fan on full 3000 rpm and lots of noise) stable under prime95. (And yes the CPU temp was cooler than the mobo, I assume because cool air was being brought in over the CPU from the duct.)

With the sp-94 and AS5 in place and a panaflo 92mm 59cfm fan blowing full speed inwards (2950 rpm) using the 3" duct provided on the system, the load temps dropped to 45c CPU and 44c mobo, idle 32c cpu, 39c mobo. I guess the heat from the CPU was heating up the motherboard and I had only had one 80mm fan blowing in, none blowing out.

Now, p4 3.2 overclocked higher to 3.84 ghz using pc 4200 memory (my pc3700 memory wouldn't go that high) stable on prime95.

Adding the twin fans sucking on the sp-94 and a 4" duct directly over the high speed center of the two fans my load temps are 38c/27c (room temp 22c) and idle 26c/27c. My hard drive temps have also fallen from 45c to 20c (which I assume means the temp measurement is a bit off for them). I can turn the fans down from full speed to 2206 rpm and the load temps go up to 41c/28c but the quiet is beautiful (certainly lots more quiet than a tornado would be) [note the dB of the two fans is not directly additive, I believe a second identical fan adds 3 dB to the noise. Hence the panaflo 35 dB fans combined make 38 dB fans at full speed.]

Here are some pics of my adpated fans. I just cut up some sheet metal to make two brackets to hold the fans together and used the supplied clips that came with the sp-94 to hold the whole thing on. Notice how the lower fan is sucking over the north bridge, and one of the air intakes of the sp-94 is sucking next to the memory. The memory and the north bridge are not warm to the touch even after a whole day of prime95.

My photos:

http://photos.yahoo.com/year1980a
 

Flakk

Member
Joined
Nov 10, 2003
Location
Oregon, USA
nice.. i need to do something like that. my chip runs at a hot 58*C under load too. perhaps ill rig something up similar :)
 

Jimbob7

Member
Joined
Jul 25, 2003
Location
Rio de Janeiro
yeh gj!! You really need to give these higher speed CPUs better cooling, my 2.4c ran alot cooler than my 3.0c even with higher vcore.
 

Phrenetical

Member
Joined
May 15, 2004
Location
1010011010
Oh yeah, my 3.0 is a heat machine, i was very surprised to find out how much heat they give out compared to the lower 2.? p4's

even oc'ed at 3.3 gig i had to add two exhaust fans and mod the back of my case to keep low temps, i hate going over 53 Max load for some reason, so thats the target i always aim to keep it under, but its hard with this chip.

My advice don't use stock intel coolers, ever. Cant wait to get my hands on a gigabyte 3d cooler pro, the one that only weighs 478grams, not 780 or whatever near kilogram weight the newer one came it at.
 

OrangeCrush

Registered
Joined
May 30, 2004
orion456 said:
As a result, I decided to use a 4" duct (dryer vent from the local hardware store) over the heat sink and the fan sucking heat from the sp-94 and blowing it directly out of the case. This means I don't have to have lots of auxiliary fans blowing air in and out. I have two 80mm panaflo fans on medium speed blowing on my hard disks and the two back fan openings are open to allow air to flow in as needed.

Are you exhausting through the side panel? I want to do this with flexible ductwork with cool air intake, but am limited to sidepanel. I would have to rig up a quick disconnect to open up the system.
 
OP
orion456

orion456

Member
Joined
May 31, 2004
OrangeCrush said:
Are you exhausting through the side panel? I want to do this with flexible ductwork with cool air intake, but am limited to sidepanel. I would have to rig up a quick disconnect to open up the system.

Yep, right out the side panel. That's the best way because you don't have any turns to cause resistance and slow the air down. My vent is solid and at 4" diameter if you have any problems positioning it, you can just reach your arm down and adjust it. I think a duct is the only way to get rid of heat fast and it forces a great air flow through the case.

I'm just experimenting with the duct, I'm thinking the duct should be about a centimeter away from the fans to reduce noise. Either that or the duct needs to be cut up a bit where my fan hubs are to allow air to flow from the outside to fill the vacuum over the hubs.
 

chasingapple

Member
Joined
Dec 23, 2000
Location
Las Vegas Nevada
I have done this before myself, I have an idea to further improve CPU temp as well as ambient temps. Instead of a small round duct from the center of both fans try a rectangle duct that goes completely around the fans, that way all the air being pumped through the fans is exiting the case instead of spilling back in. You should see an additional 1-3c off of it.

Also you might want to get cool air directly to the CPU, I also rigged up an intake fan below my CD-Rom drive and ducted it directly towards the cpu so fresh cool air was being pulled into the heatsink.

Cheers.
 

Strages

Member
Joined
Feb 26, 2003
Location
Stockton, CA
wow, that is incredibly good job on your part. Props to you!

I am really curious about how you connected each fan together - I can sort of get an idea of what you did by looking at the pics, but if you could I'd really like to know how you did it. This is definitely something that I would like to do on my air-cooled system. I have a very similar setup to yours except it's an AMD system. My temps are very good already (see sig) but with that kind of setup I think I could see a very generous drop in temps all around, which will be excellent for CA summers :).
 
OP
orion456

orion456

Member
Joined
May 31, 2004
Strages said:
I am really curious about how you connected each fan together

Thanks for the kudos. So far things continue to work great.

I've added a drawing of the metal brackets that hold the two fans together. The two brackets have tabs with holes drilled in them and are then screwed into the fan casing's regular holes. The drawing can be viewed at:

http://f2.pg.photos.yahoo.com/ph/year1980a/detail?.dir=/ef5d&.dnm=ee90.jpg

Hope that answers your question.

If the above link stops working, here is the alternative:

http://photos.yahoo.com/year1980a
 
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veryhumid

Member
Joined
Apr 22, 2004
Location
New Hampshire
A dimensioned drawing!!! Good show! :attn: I made a custom fan bracket for my wave master to hold a tornado where the blowhole goes, I should have saved the sketches. Those drawings are very handy to someone who doesn't want to screw up the first time or can take some aluminum to a machine shop. Nice work!
 

Strages

Member
Joined
Feb 26, 2003
Location
Stockton, CA
lmao - your name is "thenerd" and it's too complex. Classic :)

*note: not meant as a personal bash - just good humor
 

Jognt

All round good guy
Joined
Aug 24, 2003
Location
Netherlands
wow, that looks really good, i can understand how that would increase the airflow in the center of the heatsink..

Just one thing though.. have you tested it with the fans blowing down onto the heatsink aswell? (looks like they're sucking through the HS) i think that you should be able to get even better CPU temps.. though your overall temps would increase without a good exhaust system...

looking very good! if you would like to try it in the blowing way, id be interested in the results!
 

iwillburnbush

Member
Joined
Jul 18, 2004
I would try and make a funnel shapped shroud and get both fans to blow onto the heatsink at full blast, using the duct as an intake. That way there's no dead zone, you are pushing cold air through the heatsink and you double the airflow. You could even make like a "Y" shaped duct.

The point is, if you use both fans more efficiently, it will in turn make a much more efficient system, effectively dropping the temperature even more. What you're using now is fairly impressive, and it may work better than what you had, but it's running at less than 50% efficiency (probably more like 35-40%). If you boost that to 80-90%, then you'll have a gem...
 
OP
orion456

orion456

Member
Joined
May 31, 2004
iwillburnbush said:
I would try and make a funnel shapped shroud and get both fans to blow onto the heatsink at full blast, using the duct as an intake.

I tested out several different configurations:

http://www.ocforums.com/showthread.php?t=319423

And I also tested the funnel idea. Unfortunately unless you have a long funnel most of the air gets reflected back up to the fan an cancels incoming air. Once you make the funnel long enough it works, BUT your air velocity goes way down because it had to push all the air in front of it to get to the HS. The result was actually higher temps on my sp-94. Maybe on something like the xp-90 where you have a bigger surface to blow on it might work better.....another experiement when I get one of those (not until the new ones come out for the new p4 sockets).

I haven't tried turning the dual fans around yet because I need to make a new bracket and the new brackets have to be able to hold the force of the clips are well. That's quite a bit of work just to see if I get a few more degrees out of it.....so when I get excited, maybe I will try it out.

I would also like to try turning the fans 90 degrees because theoretically the air flow should be concentrated at the center of each sp-94 cell. Right now only a few cells are getting that effect with some cells having a relative vacuum near their centers. I think the efficiency goes up, and you might get better cooling. However, that will require new brackets AND a possible mod to the sp-94 if it worked (because the bits of copper that currently hold the fans from slipping sideways would have to be shaved off. Don't know I want to mangle my sp-94 just yet.....thinking though....
 
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