2in1 exhaust fan & cpu fan?

mikeraach · Post by **mikeraach** » Sun Mar 20, 2005 11:29 am

I'm looking at getting the LX-6A19 case. Originally I was thinking of having a 120mm in the front, 120mm in the back, and a 92mm fan on my cpu. I also have a psu that has a 92mm fan on the bottom.

However, where the rear fan is place, it will be right next to my cpu fan. I know this setup will cause turbulance and noise. I know many people with this setup chose to put the cpu fan in the sucking mode to allow the rear fan to pull the hot air from the cpu. The psu will also help pull some heat from the cpu as well.

My question is, could I make a duct from the 120mm exhaust fan directly to the cpu heatsink and remove the 92mm fan on my heatsink? This would get rid of the turbulance from the 3 fans being so close to each other, would still act as an exhaust fan pulling air from inside to the outside, and directly get rid of the heat from the cpu.

Has anyone tried this? How were the results? Did the cpu get cooled as well as having the fan on the cpu and an exhaust fan? Did case temps suffer because the exhaust fan was being restricted by the cpu heatsink?

Tibors · Post by **Tibors** » Sun Mar 20, 2005 12:42 pm

This one was posted yesterday: http://forums.silentpcreview.com/viewtopic.php?t=20537

Bluefront posted some threads where he used an Alpha PAL cooler with an aluminium dryer duct. There is an article in the main site's DIY section about a setup which uses "counter current crossflow", which is just difficult words to describe what you want. If you search a bit on the forums you'll probably find more examples.

You have to watch how you construct the duct or it might block the PSU fan.

Bluefront · Post by **Bluefront** » Sun Mar 20, 2005 3:22 pm

There are many ways to do this....Here's the duct Tibors referred to. Some of the photos show it attached to the rear exhaust fan (no fan on the CPU). In it's final form it attaches to the PSU bottom 120mm fan (again no fan on the CPU).

This setup works perfectly.....maybe my favorite project. I think there's 90 photos in that album.

mikeraach · Post by **mikeraach** » Sun Mar 20, 2005 5:11 pm

Right, I know what I am talking about is possable, and I even have a few ideas on how to do it.

What I am wondering, is the performance/noise of both setups.

Will ducting the exhaust fan to the cpu heatsink (and removing the cpu fan) still cool the cpu the same? Will doing this still allow enough air to be pulled in the case?

Or will having an exhaust fan, with a cpu fan (sucking) provide the best setup for cooling (with still minimal noise)?

Bluefront · Post by **Bluefront** » Sun Mar 20, 2005 5:35 pm

Actually you probably wouldn't gain much with two fans. Having one exhaust fan pulling air off the CPU heatsink works perfectly for me. Having a heatsink that works well in the "suck" mode is the way to go. An Alpha 8942 is enough to cool a Prescott with this setup.

Make certain the duct is a tight fit, with a smooth, unobstructed airflow path....that gives the best result.

Oh... how well does it work? I can run the whole computer off one 120mm fan using that duct setup.

mikeraach · Post by **mikeraach** » Sun Mar 20, 2005 7:57 pm

Bluefront, have you tried your setup with a fan on your cpu and an exhaust fan? If so, what was it compared to using the duct?

Bluefront · Post by **Bluefront** » Sun Mar 20, 2005 11:16 pm

Nope.....It was/is a size limitation. Due to the large size of the duct, I cannot fit an 80mm on top of the Alpha and attach the duct, then get it to fit in any case I've seen. You'd need a case about 9.5" wide.

If you used a flexable duct, maybe you could do it....but it's totally un-necessary. One fan on the case end of the duct is enough.

mikeraach · Post by **mikeraach** » Sun Mar 20, 2005 11:45 pm

Oops, I guess I should have been more clear.

Have you ever tried having a fan on your cpu, and a fan for exhaust WITHOUT the duct?

Bluefront · Post by **Bluefront** » Mon Mar 21, 2005 3:32 am

Well sure....the standard setup has a fan on the CPU and another case fan in the rear, and a third fan in the PSU. I used to build computers like that.....but no more.

Using ducts to exhaust heat directly off the CPU, keeps the rest of the system cooler, keeps the CPU cooler because hot air is not recirculated, and makes the whole setup quieter because of fewer fans, and better use of available airflow.

But because of so many variables, it's difficult to compare various systems as to heat, and noise. But ducting does work if it's installed correctly.

Shriek · Post by **Shriek** » Tue Mar 22, 2005 12:26 pm

Just in case it's not clear from the earlier posts, you'll want to make sure your heatsink of choice works well in reverse mode before trying this. Many of the newer sinks work well both ways, but (if I understand what I've read here correctly) many suffer when the airflow is in the "non-standard" configuration.

The Alpha that Bluefront mentioned is known to work well, as are the new aluminum heatpipe coolers from Thermalright (and a handful from other manufacturers). I use the XP-120 ducted as such with beautiful temps.

mikeraach · Post by **mikeraach** » Tue Mar 22, 2005 4:25 pm

I have a sp-97 for my xp2500 (running on NF7-S board). I seem to remember reviews saying it didn't run quite as well in the suck mode, but I can't find any of them.

The only thing I'm wondering about is the ducting from a 120mm to fit over my sp97--in that it'll create resistance and possably more noise (and less airflow).

Shriek, do you have any pictures of your current setup? I've been also debating upgrading my setup and getting a nf3 board with a 939 chip and xp-120.

Shriek · Post by **Shriek** » Wed Mar 23, 2005 11:04 am

mikeraach wrote:Shriek, do you have any pictures of your current setup?

Not yet, but I hope to soon. I was going to take some when I last had my case open, but I got busy taping up holes and playing with air pressure changes--quick temp tests suggest that I may be able to get by with forcing air through the CPU HS with the intake fan rather than the exhaust, and that's with the unpowered exhaust fan in the way (haven't replaced it with a shell due to a misplaced bundle of zip-ties

)

I'll try to finish up tonight if I can manage to stay away from WoW....

Shriek · Post by **Shriek** » Thu Mar 24, 2005 9:28 am

I don't mean to advertise a thread, but since you specifically asked for pictures, I put them here.