For 80mm fan what is more important, CFM or RPM?

[davidos]

I am using a 80mm fan on my sk6. Do I want higher RPM or higher CFM? Also, if I overclock what is the highest speed (or cfm) fan I can get that's quiet?

 

[WaTaGuMp]

They pretty much go hand in hand, the faster the RPM the more air it puts out. If you look around you will see that the quiter fans will produce lower CFM, cause the spin slower. Their are several things you can do when it comes to fans and output. You can go with Panaflo L1a's they are quiet but also produce lower CFM. You can also get higher speed fans and get a fanbus, which allows you to tune the fans to speed and the amount of noise they make. If it it too loud ten turn it down simple as that. They also have smart fans out there that connect to the mobo connections that can adjust automatically to the speed that the computer feels it needs. Unfortunately there is no solution to have both high CFM and low RPM its just simple science, the faster it spins the more air it will push in most cases.

 

[davidos]

Thanks WaTaGuMp.

How can an 80mm fan at 1600 rpm put out 27cfm when a 80mm fan at 2150rpm only put out 25cfm?

 

[WaTaGuMp]

Well that depends on how accurate the numbers are. It is very common to see numbers about fan RPM and the CFM they put out to be wrong. I guess its possible if the blades on a fan design suck they wouldnt put out very good CFM, but thats pushing it since most fan companies know how to make fans. Lets look at it this way if you take 2 airplane propellers of the exact same size and design spin one at 300 RPM and another at 800 RPM which do you think will move more air and make more noise? Im betting the 800 does. 😉 So dont believe everything you read when it comes to fan speeds and CFM, I have seen plenty of articles about this fan does this RPM and this CFM and when people try them they dont do what they say they do. But unless you have ametter sitting around that can tell you how much CFM a fan is putting out then just listen to what others have tried and go with what seems to work for most. I have 2 intake 2 exhaust both 80 mm in my case, plus 2 more in the PSU, and I dont really pay attention to the CFM they put out. As long as my comp runs all day and never overheats then I must be flowing some air through the case. Most everyone that decides on fans do so more for the noise issue then anything else, cause when it comes to case fans the Antec, Panaflos, Sunon, ro whatever you go with should move enough air to keep your computer happy.