I've recently made some major modifications to my rig, including replacing the noisy fans on my video card with some quiet ones, and changing the positioning of my fans. One of my goals was to add a 120mm fan at the front of my P183 case to blow across the GPU to help keep it cooler and try to vent some of the hot air out the back of the case.

I decided on a 120mm scythe 800rpm fan based on its noise profile. Overall i'm decently happy with its noise output. However, I was sorely disappointed at the results on the GPU. It did not decrease in temperate at all. After placing my hand over the gpu to see just how much airflow was coursing over it from the newly installed fan, I realized that there was almost NO air reaching it. I had to take the fan out, run it bare to find out exactly why - the fan does not blow "straight". Here is what i mean.



Bottom line is, the fan blows most of its air diagonally out to the sides rather than straight ahead. Most of the airflow is hitting either the bay above it where the DVD drive sits, or the separation area below it where the PSU lies. Very little actually goes straight out and hits the GPU.

Now, I can probably counteract this affect by getting a high RPM model that would blow SO much air, that enough will eventually reach the GPU. However, that would defeat the purpose of a nice quiet rig. So my question is, does anyone know of any nice quiet fans that tend to blow more horizontally straight? I assume this has to do with the shape of the blades.

Silverstone Air Penetrators.

Moving air naturally expands into calm areas so this is the same for any similar construct. The increased airflow through the case will still be of general benefit, but to achieve significantly improved cooling for a graphics card you can either make some sort of duct(cardboard is popular) or put a fan close up to the card. A few fans have incorporated grates that helps guide the airflow in a more straight line like the Silverstone Air Penetrator. They aren't low speed however and forcing air through a shaping vent invariably leads to some level of increased noise. Better to simply move a fan close to where it's needed, in my opinion.

If the card really needs more direct airflow that is.

Cardboard ducts work wonders

Dyson FTW....
http://www.mydysonfan.com

It might have a negative impact on the noise level but you could buy an airflow straightener such as these: SaxonPC, Nexus.

Thanks for the help guys. A duct seems like the most practical solution, but unfortunately there is too much stuff in the way for me to be able to use one.

Something like the Nexus beamair seems like an interesting solution, but i'm somewhat skeptical of something only about 0.25" thick having any real impact on the direction of airflow. How well do these things really work?

Ducts and air straightener filters are options but lets not jump the gun. You say you went scythe 120mm 800 rpm but you didn't say which one. They make 12mm thick, 25mm thick, and 38mm thick in a number of motor/blade combinations.

I'm assuming you didn't get the Slipstream Slim SY1212SL12SL. If you did swap it out for a 25mm thick fan and your problem is solved. Just in case that still doesn't stand out

SY1212SL12SL = super thin fan
SY1225SL12L = normal thickness fan

I'm guessing you got the Classic fixed RPM Slipstream SY1225SL12L or the S-FLEX SFF21D since both are 800 RPM and more commonly discussed. But you may have gotten the GentleTyphoon D1225C12B2AP-12 which is also 800 RPM. You may find that if you got a slipstream or gentle typhoon that getting a SFlex or Kama Flow will give you more direct airflow that you desire. If you got the S-Flex and it isn't direct flow enough for you you could try the others in 25mm thickness (Kama Flow 2, Slipstream, Gentle Typhoon) or try a 38mm thick fan.

They only make one style of 120x38mm fan though. It comes in 3 RPM choices but the only one to consider for quiet use is 1000 RPM. It's the Ultra Kaze DFS123812L-1000

In CPU heatsink reviews you'll sometimes see mention of how a fan handles resistance. Maybe they'll say it in terms of pressure, or in terms of RPM in free air vs RPM installed, or maybe in some other way I'm not thinking clearly enough to write about. Anyway the slipstream doesn't deal with high resistance as well and I'm guessing that is because of this non straight airflow you are noticing. That's also why I'm suggesting you might like the SFlex or Kama Flow series better but until you specify which fan you have I can't make better guesses.

But no matter what I say if you can afford to just go buy some of the other choices and try them you can tell us what works for you. Hopefully this post will at least get you started on figuring it out.

The ones I purchases are the SY1225SL12L slipstream type. One is installed in the rear exhaust position, and one in the front intake position. The rear exhaust works fine. I just wish the front intake had a more direct airflow directly over the GPU.

I have not checked the prices of these air straightenrs, but I assume they would be significantly cheaper than buying an entire new fan. Though if getting a new fan is the best option, I will certainly consider it. What would you recommend as the best option?

I don't know where you are so check prices shipped to you for

S-FLEX SFF21D 800 RPM*
KAMA FLOW 2 SP1225FDB12L 900 RPM about $20 after shipping to my zip code
ULTRA KAZE DFS123812L-1000 1000 RPM about $25 after shipping to my zip code

* The S-FLEX series has been discontinued but is highly regarded. If you can find it cheap on closeout somewhere buy it. Back when it was new $15 was a good price. Now you might have to pay more.

But if you can't afford any of those you can just grab my favorite old standard for a cheap fan

YATE LOON 120mm Case Fan - D12SL-12 1350 RPM about $10 after shipping to my zip code

Try it at 12V and if you don't like the ever so slight noise from it you can use an adapter to run it at 5V and then it'll be silent. The other nice thing is they are only about $4 a piece so once you pay shipping you can grab a 2nd or 3rd really cheap. It's my go to fan for low budget systems.


Oh, and the beamair type filters that I checked on were more expensive than just ordering a Yate Loon so I can't see them as a great value compared to getting a fan better suited to your needs (and making your own duct(s) is cheapest of all at free assuming you have some materials laying in a recycling bin that you can harvest or material that you can keep instead of tossing in the bin)

It looks like a good answer except the lowest RPM model I saw was 1500 RPM. Do you know if the starting voltage is below 5V?

http://www.silverstonetek.com/product.p ... 57&area=en

Oh, and by comparison it was about $25 shipped to my zip code.

This review shows it with a 5v,7v,12 molex to 3 pin adapter. If that is included with each fan I'm guessing it'll start at 5V reliably.


viewtopic.php?f=9&t=59318 is the thread for this fan if you get one or have one chime in there.

Have you tried changing all your fan vents to intake? I experimented with this, and it appears to force air out through some open expansion slots, and helped stabilize my system which has a passively cooled half-height Radeon 5750 in a half-height MATX case (not for the faint hearted).

Before, I must have had dead hotspots with the conventional intake at the front and exhaust at the top because i was getting blue screens everywhere at the most random times. When I switched my exhaust to intake, all the issues disappeared, and I could even feel the hot air by the expansion slots.

This requires that your case be quite sealed; in my case (pun intended) all the large open areas were covered with intake fans.

No idea. I use T-Balancer bigNG, which starts all fan at 12V and then slows them down. They are running at ~650-700RPM@5V in my case.