How much airflow do I need? Lian Li 351

[Skunkwourk]

Im planning to put a Phenom x4 905e and Silent Cell 5750 into a Lian Li 351. I also have the Scythe Mini Ninja as a passive CPU cooler. Therefore the only fans I would have running are 2 120mm in front and one 80 in the back. I was hoping I could replace all the fans with S-flex fans rated at about 20 dba to keep it quiet but Im a little concerned about their efficiency.

The Phenom is 65W so hopefully that doesn't run too hot and I don't plan on overclocking. As for the Silent Cell I've read that it can get hot but with "good" airflow I shouldn't have anything to worry about.

Does anyone have any idea what "good" airflow or what fans would be ideal for my setup?

 

[IGemini]

The 351 has more fans than most other cases its size. And Lian Li's site says they're rated to be fairly quiet (1000-1200 RPM). I don't think switching to those S-Flex fans would be much of an improvement. Airflow and RPM are always traded off with noise level.

 

[MrK6]

The problem with the V351 isn't the intake, it's the exhaust. If you can do the 92mm exhaust fan mod and open up the grill right behind the CPU socket, it will work wonders.

 

[zagood]

The problem with the V351 isn't the intake, it's the exhaust. If you can do the 92mm exhaust fan mod and open up the grill right behind the CPU socket, it will work wonders.

An easy, effective, but ugly way to do this would be to get a 80mm to 120mm adapter, place on the outside of the case, and mount a 120mm fan (will probably want a wire grill too) as exhaust on it. If you can fit it inside, great, but on the outside it'll a) leave more room inside and b) be more efficient pulling through that diameter reduction instead of trying to push.

 

[geofelt]

I just finished a sandy bridge build with the V351.
I have a GTX580 which fits with room to spare, and a 2600K.
I planned on using a noctua u9b cooler, but it was a couple of mm's too tall.
I got a silenx compact tower cooler which fits, just without the need to mod the case.
The stock lian li fans are good, and do not need replacement. They provide sufficient intake airflow for most anything. The key to good cooling is to get the hottest air out of the case as quickly as possible.
The GTX580 has dual slot direct exhaust and is relatively quiet. I suggest you look for a graphics card with direct exhaust. Something like this:
http://www.newegg.com/Product/Produc...82E16814161352
On the cpu side, you could try a passive cooler, but I think you would do well to get some airflow. A slow turning fan will be quiet becase it is buried deep inside the case.

I constructed a cardboard duct to direct the cpu cooler air towards the rear vents. There seems to be good airflow out of the vents, and cooling is close to what it is with the sides off.

 

[Skunkwourk]

Thanks for the advice. I ended up leaving the stock fans in there and Im pretty happy with it as is. After some cable management and time for the AS5 to cure a bit my temps are about

Idle
38 CPU
40 GPU

Load
52 CPU
70 GPU

Not too bad for Stock fans and purely passive heatsinks.