Does running at fan at 7V reduce it to roughly 7/12 of it's CFM output? And is 18.7 CFM enough to cool a 1Ghz TBird?

[Noriaki]

Ok here's the deal.

I have a 32cfm 26db 80mm fan.

I'm going to attach it to either an Global Win FOP32 heatsink or an Alpha PAL6035. I'm not sure how loud the 26dbA will be (my only other fans will be an Enermax Whisper 430watt) so I may knock it down to 7V.

If I knock it down to 7V will that reduce the CFM output to ~18.7CFM (7/12 of 32)?

And is that enough to keep a 1Ghz TBird cool when paired with one of the above heatsinks (and Arctic Silver II)?

I favour the GW FOP32 becuase it has that little ridge so it should be easier to attach the 80mm fan, but if the Alpha is alot better I'll consider using it.

 

[mechBgon]

I looked at the output graphs for a Panaflo M1A 80mm fan here to get an idea of the effect of running at 7 volts. According to the graphs, it appears to cut the flowrate in half at 7V compared to 12V.

On the other hand, 26dB is not very loud to start with. Maybe you'll find it's ok at 12V.

 

[Charles]

Noriaki, Alpha PAL6035 with a 18CFM fan is enough to cool a 1 - 1.1GHz Thunderbird. This is what I use to cool my 1066MHz Thunderbird on an Epox 8KTA3+.

 

[Mykex]

Might I suggest switching between 12v and 7v for the warm day of heavy gameplay? I have way too many fans(15)each having a good excuse but the amount of flow @12v wasn't needed. After setting my HD coolers(6 tiny fans)on 5v my main intake and chipset @7v I am much happier with the noise level. I am now also considering 7v for the side intake and the 80cm mod @7v. for my Fop32. I just want to squash the last hint of whine and get a nice "whitenoise" type sound but I would like to have it switched JIC.

 

[pbox]

Not so fast. 26dB is not loud, not the quietest but close. If you put and 80mm fan on the heatsink it will blow underneath you CPU socket and invalidate the temp readings. Just because you will see lower temp readings it might not be such...

If you use 7V to run the fan: the voltage-CFM in NOT linear. If you decrease the voltage it will decrease the CFM but not in the same ratio. Also those motors have a min limit on the starting voltage. They might run on 5-7V but they need 7-10V to start. And it it does not start you have about 5-10s before CPU meltdown (physical, unrecoverable). Try 10V or around. Measure voltage with the fan running!!!

Peter

 

[EvilDonnyboy]

I wouldn't say it'd be 7/12 the output if u put it on 7V. It depends on fin design and other factors.

Just think, If you were driving a car 100mph at full throttle (manual, 3rd gear or whatever) than u put it to 1/2 throttle. You would't just end up running at 50mph. There are variables.

 

[Noriaki]

Lots of people have fans running at 7V, Mikewarrior2 has a 92mm fan at 7V, so I figure my 80mm should be ok.

I don't care that much about temp readings...I don't even my thermal probe installed right now.

I'd try 10V but how do you get it?

You are given +12, +5, and two Grounds (+0V) on a standard molex. The fans power lead to +12 and ground lead to +5 nets +7V, but how do you get 10V? 12,7,5 I think are the only combinations you can make.

 

[johneetrash]

a rheostat maybe i think somewhere someone did a test (i know it was on the front page of hardocp) on the delta fan, hooked up a rheostat or something to lower the voltage... said at around 9v there was a noticable drop in noise with no noticable drop in performance, maybe 1 or 2 degrees.. i wanna do that