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Fans and Molex Connectors

M

manutdc

Member
Hey everyone,

I've been looking at this fan (http://www.newegg.com/Product/...x?Item=N82E16835103063) as a case fan. According to Cooler Master the fans move 70CFM at "stock speed," and I'd need a fan controller to get it up to 90CFM. Is that only if I plug in the fans with the 3-pin connector? If I plug in the fans to a 4-pin molex, will they run at the full speed or will they run at the supposed stock speed?

Any help would be appreciated, thanks in advance!
 
The only way to change fan speed (and hence CFM) is to change the voltage sent to the fan.
And since 2 pin, 3 pin and 4 pin (molex) connectors all supply 12 volts, the fan will run at the same speed no matter how you connect it. Fan controllers also supply 12 volts only.

While there are ways to overvolt a fan, the fan's lifespan will be shortened ...significantly.

Just get a higher CFM fan.
 
Hm, okay, thanks for the info! Now I'm just curious what they're trying to do with the 70CFM "stock speed" while saying it can get up to 90CFM. I'd imagine stock speed would be the highest it could run, since there's no way to change it without increasing the voltage...
 
What im wondering is why 90cfm is the breaking point here? 70 is alot, but i mean if you only got one fan exhausting, I could see it making a pretty big diff.
 
One thing you need to be aware of with CFM is static pressure. 70CFM does not mean when you put it in your case it will put out 70CFM. That is how much air it moves with nothing in front or behind it and no pressure pushing against it. It has been a peeve of mine that case fan makers do not normally list static pressure ratings. Without it the 70CFM fan could be worse than the 50CFM fan.


This is one of the few fans on newegg that shows pressure rating.
http://www.newegg.com/Product/...x?Item=N82E16835129245


The part:
Static Pressure: 0.072 Inch-H2O


That means the amount of pressure that a fan can no longer produce any air. The best fans are around .099, this one is .072 so it does pretty good at pushing against pressure . Realize that at .072 that it doesn't put out no air. On a graph it is almost like a curve, the more pressure, the less CFM. So it pays to find the fan with the highest pressure rating to be sure you get as close to the rated CFM as possible.

Especially if you place filters over fans because that can cut their CFM in half or more.
 
Originally posted by: Narynan
What im wondering is why 90cfm is the breaking point here? 70 is alot, but i mean if you only got one fan exhausting, I could see it making a pretty big diff.
Click to expand...

Not really worried about the 70CFM vs 90CFM, just curious about what the deal is with the "stock" speed and "full" speed...seems kinda misleading.

Originally posted by: Modelworks
One thing you need to be aware of with CFM is static pressure. 70CFM does not mean when you put it in your case it will put out 70CFM. That is how much air it moves with nothing in front or behind it and no pressure pushing against it. It has been a peeve of mine that case fan makers do not normally list static pressure ratings. Without it the 70CFM fan could be worse than the 50CFM fan.
Click to expand...

I checked around the Cooler Master forums and the static pressure is apparently 2.94mmH20 or 3.04mmH20. I'm not sure if these values are good or bad though...
 
Originally posted by: manutdc


I checked around the Cooler Master forums and the static pressure is apparently 2.94mmH20 or 3.04mmH20. I'm not sure if these values are good or bad though...
Click to expand...

To convert from mm H2o to inch H2o you multiply x .04 so the fan is .11 h20inch at worst and .12 at best , which is pretty high.
 
That's good to know then, thanks! For future reference, is there some kind of range I should consider for static pressure?
 
Originally posted by: manutdc
That's good to know then, thanks! For future reference, is there some kind of range I should consider for static pressure?
Click to expand...

Think of 1 mm h20 as the bare bottom low quality and 5 mm h20 as the ultimate.
 
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