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Anybody game for an experiment...

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April 1, 2003 3:40:23 AM

Ok, I've been messing around with a bit of an experiment and I'd like to see if some of you can replicate my results...

It occurs to me that one of the limitations of the fan on fins coolers is that they can recirculate their own air... that is to say the fan forces air down on to the fins which then blows out the bottom and circulates back up from the motherboard toward the fan, which grabs some of this warm air and blows it back into the cooler... It crossed my mind that preventing this would probably lower CPU temps somewhat.

Inventive sort I am, I said... Ducting! Get the fan's intake air from someplace other than right on top of the heatsink.

Here's what I did...

I took a file folder (nice middle weight cardboard, pretty colours :smile: ) and cut a strip about 5cm (2" wide) long enough to fit all the way around the fan. I then wrapped it around the fan making sort of a square chimney standing up above the fan, folded the corners and taped it to itself so it was removeable without much difficulty. (think of a small square chimney sitting on the heatsink with the fan inside)

Ok, fire up the system and let the heat stabilize... 44c
Slip on my little fan shroud and let it settle... 42c

Next try this with the case closed, shroud off... 46c
And finally case closed, shroud on... 42c

Repeat... same results.

Anyone else like to try this and let me know what they get?
I'd be very interested to see if this is a fluke or not...



--->It ain't better if it don't work<---

More about : game experiment

April 1, 2003 3:54:06 PM

Interesting idea and I would try it, but alas, I have moved on to watercooling :smile:

But I will get someone else to try!

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... And I'm proud to be an American, where at least I know I'm free, and I won't forget the men who died, who gave that right to me.
April 1, 2003 4:32:20 PM

Watercooling... hmmm... what a convenient excuse :smile: .

I really would like to see if this is a fluke or if it's something that may help... so I'd be interested in as many results as I can get.

On my system it knocked the CPU down 4 degrees. Hardly something to get all excited over but if it's consistent in lowering temps on other systems, it might actually be something worth further developement.



--->It ain't better if it don't work<---
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April 1, 2003 4:35:32 PM

I am building a system for my girlfriend soon, I can try it out and see how it works, but may be a month or more bafore I can get all the parts she needs.

and hey, 4 degrees can be the difference between an overclock and a failed post on an athon, and on a p4, make it autothrottle down.

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... And I'm proud to be an American, where at least I know I'm free, and I won't forget the men who died, who gave that right to me.
April 1, 2003 4:57:49 PM

Exactly...

The thing that got my attention was that in the case-closed test my CPU temp stayed the same as it was with the case open. I think this reflects just how much recirculation of hot air does go on...

I guess the next step is to try different designs --shapes, sizes, air paths etc.-- to see if one works better than others... but for now I'm content just to see what happens when the air recirculation problem is reduced.

I suppose at some point I'm going to have to cut a hole in the side of a case and McGiver up a duct to bring outside air directly to the CPU fan. That will also be an interesting experiment.

But for now... I just want to see if others get similar results.


--->It ain't better if it don't work<---
April 1, 2003 5:02:46 PM

Ive seen attemps (and decent ones) in the past at ducting cool outside air at the cpu. One notable one is an old dell my boss has at his house that directs air via an 80mm fan from the back of the case through a duct across the slot 1 heatsink.

what interests me the most is the idea of just putting a small chimney as you call it on the fan. Quick, draw it up and patent it!

<font color=red>*</font color=red><font color=white>*</font color=white><font color=blue>*</font color=blue>
... And I'm proud to be an American, where at least I know I'm free, and I won't forget the men who died, who gave that right to me.
April 1, 2003 6:16:49 PM

Heh, heh... naaa... this is a trick I'd rather give away than patent.

If it works every time, it will show up on "new and improved" coolers no matter what I do. They'll change the shape of it a little and re-patent it as an improvement and before I ever get the money together for a production run, 13 companies will already be outselling me 100 to 1.

I wouldn't stand a chance in that market...



--->It ain't better if it don't work<---
April 1, 2003 6:21:30 PM

It just dawned on me, you finnaly found a good use for those fan size adapters! just put them on top of the fan, instead of putting it inbetween the fan and the sink. Only prob there is you are out of luck on larger fans.

<font color=red>*</font color=red><font color=white>*</font color=white><font color=blue>*</font color=blue>
... And I'm proud to be an American, where at least I know I'm free, and I won't forget the men who died, who gave that right to me.
April 1, 2003 6:25:14 PM

Yep... that's entirely possible.

The thing is to relocate the air intake away from the hot air coming off the heat sink... to prevent recirculation as much as possible. If just screwing on one of those adaptors does the job... what the heck.

It might also work with that thermaltake "ducting mod"... but instead of reloating the fan to the intake of the tube, just bolt the tube onto the top of the fan.

I like my little shroud trick... because it's 100% cheap and dirty :smile: .


--->It ain't better if it don't work<---
April 1, 2003 6:27:52 PM

One of the reasons I sugggest the adapter is that you can get them in many colors and styles, someone might not want cardboard in the middl of his "tricked out" windowed case...

<font color=red>*</font color=red><font color=white>*</font color=white><font color=blue>*</font color=blue>
... And I'm proud to be an American, where at least I know I'm free, and I won't forget the men who died, who gave that right to me.
April 1, 2003 6:51:02 PM

Spray paint?

How about flourscent purple?

:smile:


--->It ain't better if it don't work<---
Anonymous
a b K Overclocking
April 1, 2003 8:00:30 PM

"I suppose at some point I'm going to have to cut a hole in the side of a case and McGiver up a duct to bring outside air directly to the CPU fan."

Now you are talking. Then you will have as good of cooling that blowing ambient air will allow. Just be sure your exhaust isn't feeding your intake.

The weird thing about your testing results that keeps bugging me is the fact that your CPU temps went up after you put on the side panels (see non shrouded tests). That is the opposite of what I get, in fact both my CPU temp and M/B temp drop by a couple degrees C when I add the side panels. A bit strange....
April 1, 2003 8:21:11 PM

i guess your case is designed for better airflow with the panel on
if you've got two fans in the front and two in the back drawing air across the motherboard upward, that'll have a good effect
when you take your side panel off you're probably losing that effect
then again if your case isn't setup like this then my theory is for naught
before i got watercooling my casefan setup was pretty crappy and temps were lowered a few degrees by taking the side panel OFF

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April 2, 2003 12:28:11 AM

Actually...

Both went up without the shroud... but that's because this machine is jammed into a micro-atx case.

Only the case temp went up after putting on the shroud... the CPU stayed at 42c.



--->It ain't better if it don't work<---
Anonymous
a b K Overclocking
April 2, 2003 12:36:51 AM

@$#*! That's what I meant, but I blew it!

M/B temps went up with side panel installation, not CPU temps, duh.

Yeah, it still bothers me even though I can't seem to convey any coherent thought in english today.

I am so sorry!
Anonymous
a b K Overclocking
April 2, 2003 1:13:34 AM

I guess you just can't get enough airflow through those smaller cases.

That explains it.
April 2, 2003 2:29:56 AM

Its probably possible, but difficult

<font color=red>*</font color=red><font color=white>*</font color=white><font color=blue>*</font color=blue>
... And I'm proud to be an American, where at least I know I'm free, and I won't forget the men who died, who gave that right to me.
April 2, 2003 3:43:11 AM

I didn't list the motherboard temps.


--->It ain't better if it don't work<---
Anonymous
a b K Overclocking
April 2, 2003 4:03:15 AM

You're right, that made no sense. You can basically disregard my last 2 posts. I had misunderstood your reply to me. I shouldn't be posting when I am tired like i am now.

I do plan to run your experiment soon, though. I'll post back with my results.
April 2, 2003 4:14:24 AM

Kewl.. no problem.

Looking forward to seeing your results.


--->It ain't better if it don't work<---
April 2, 2003 12:41:42 PM

Yeah, I actually tried that last year and got 3 degrees, if I remember correctly. Used part of a Wheaties box. Shouldn't make a huge difference as long as you have decent airflow through the case, keeping the air being blown off the HS/CPU from doing too much hanging around, anyway.

You're right, spray paint would make it look just fine, for anybody with a window case.

War Eagle
April 2, 2003 2:20:10 PM

Thanks... 3 degrees... not bad! Wheaties box? Hey, why not :smile:

I did this to a couple of other computers last night and got 2 degrees on one and 5 degrees on the other.

You are right that increasing airflow through the case would make some difference... the computer with the 2 degree response had extra fans front and back (total of 3 case fans +PSU).

As I explained elsewhere in the thread, I'm operating on the theory that reducing recirculation of hot air is why it works.



--->It ain't better if it don't work<---
April 2, 2003 5:40:58 PM

Heh, heh! It was actually about a 10-year-old Michael Jordan Wheaties box....with the Wheaties still in it and sealed. Don't ask.
Hey, it was the closest thing at hand. I didn't have any nifty bright, solid-colored file folders.

War Eagle
April 2, 2003 6:26:20 PM

Well, at the risk of quoting Bill Cosby... "Mahn's is green and yers is arange"... I bought a mess of coloured folders a year ago with the bright idea of re-sorting my filing system using colour coding for quick recognition of who had which machines... between earning money and messing about on BBSs while waiting for burn ins and stuff I've just never gotten around to it... so I have about 1000 folders that have become "raw material" for these silly kinds of experiments. My latest incarnation of this fan shroud is a bright blue... maybe I'll try green next and see if it makes my CPU go faster :smile:

BTW... that 10 year old Wheaties box may well have been worth more than the serial inside it!



--->It ain't better if it don't work<---
April 2, 2003 8:32:48 PM

Much more. I was in a weird mood that day and was trying to make some room in my closets. Kinda regret doing it, but I've still got another one.

War Eagle
April 2, 2003 8:44:49 PM

Well... next time you get hungry, stay away from your closet.

:eek: 

--->It ain't better if it don't work<---
April 3, 2003 1:14:46 PM

HA! Ya know, I also had a collection of various Coke bottles (Japanese, etc) that were all at least 10 years old, and I got curious and tried one of those....man, that was AWFUL!!! Think I learned my lesson from that.

War Eagle
April 4, 2003 4:55:29 AM

i think my particular setup is very close to being ducted...

the 80mm 3200rpm panflo fan pushes air downwards onto the mcx-462.

diagonally above it, between the cpu and the gpu is the side casefan hole, without a fan, just a bare shroud.
behind the cpu is 2 x 2000rpm panaflo's, removing lots of air.
Current CPU temp is 63C (not really 63C, its a bug of the 8K3A+ that overreports temps. Can get up to 86C).
If i cover the side hole the cpu climbs to 66C in around 5 minutes, and i feel greater draw through the front 2 fanholes.
the suction felt on the bit of paper covering the side hole is enough to keep it on without me holding it.


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