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Is this TOO much positive pressure?

Qu9ke

Junior Member
Sep 27, 2014
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I've been deliberating on what fans to include in the Thermaltake Core V21 case. I've thought of replacing the stock 200mm fan with one that has blue led, and I've thought of putting a 140mm blue led pwm fan in the rear as exhaust. The 200mm fan's cfm is 148.7 while the 140mm fan's cfm is 20-97. My question is this: Is the difference between the two's cfm too great leading to too much positive pressure, or am I worrying over nothing?
 

UsandThem

Elite Member
Super Moderator
May 4, 2000
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or am I worrying over nothing?
This. Cases are not totally sealed to begin with, and having one intake and one exhaust will not be an issue.

Plus, CFM has nothing to do with static pressure. That is measured differently, and both figures are usually provided by the fan manufacturer. In general, the bigger the fan, the lower the static pressure it provides.

http://www.overclock.net/t/737319/static-pressure-vs-cfm

http://www.tomshardware.com/answers/id-2175016/high-airflow-fans-static-pressure-fans.html
 

UsandThem

Elite Member
Super Moderator
May 4, 2000
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Also, I forgot to add I have three 140mm intake fans, and one 140mm exhaust fan.

My PC hasn't exploded, or imploded yet. ;)

Your PWM exhaust fan will likely start in the 650 RPM area (if you use a 'normal profile in your BIOS). It will increase as needed for temps. Your 200mm fan will move a good amount of air, but it will likely spin at a constant, lower RPM speed. That's what I have observed in my son's Thermaltake case (which also has the same size fans as yours does). It also stays relatively dust free.
 

aigomorla

Cases and Cooling Mod PC Gaming Mod Elite Member
Super Moderator
Sep 28, 2005
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Thermaltake Core V21 case
do you know how open that case is?

Positive pressure?
I will tell you this now... in that case it is impossible unless u start duct taping the hell out to close air gaps.
 

Qu9ke

Junior Member
Sep 27, 2014
20
0
16
do you know how open that case is?

Positive pressure?
I will tell you this now... in that case it is impossible unless u start duct taping the hell out to close air gaps.
...Touché. Yeah for some reason the openness of the case completely slipped my mind.
 

UsandThem

Elite Member
Super Moderator
May 4, 2000
14,470
5,029
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do you know how open that case is?

Positive pressure?
I will tell you this now... in that case it is impossible unless u start duct taping the hell out to close air gaps.
...Touché. Yeah for some reason the openness of the case completely slipped my mind.
Challenge accepted. I think this would create "too much positive pressure" for that case ;)

3,300 CFM


Seriously, I looked at the detailed pictures of that case after aigmorla responded, and that is one very open case.
 

BonzaiDuck

Lifer
Jun 30, 2004
14,833
1,013
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I've been deliberating on what fans to include in the Thermaltake Core V21 case. I've thought of replacing the stock 200mm fan with one that has blue led, and I've thought of putting a 140mm blue led pwm fan in the rear as exhaust. The 200mm fan's cfm is 148.7 while the 140mm fan's cfm is 20-97. My question is this: Is the difference between the two's cfm too great leading to too much positive pressure, or am I worrying over nothing?
That cannot be a CM 200mm LED fan. I think those things are only worth about 90+ CFM. There is an NZXT ~200mm fan that provides as much as 160 CFM. There is a 200mm red-LED fan -- name of which I can't recall at the moment -- was fairly decent at about 90CFM. Of all those, the best I've come across is the BitFenix Spectre-Pro LED 200mm series with the CFM maximum spec +/-10% was 148.72 CFM.

I like the green ones. I never had a Red thing for case lights, and my Blue thing lasted only a short time -- upon which I foreswore Bling until my Skylake build. Which -- is green.

But I'm using the 140mm green LED Spectre Pros x2, plus Akasa Viper "square" 140mm units in my Skylake project (no LED but yellow fins which work with the green light). One of those latter had developed a slight noise, but somehow -- I think it has disappeared. If I have the chance, I'll give the system a once-over with my mechanic's stethoscope.

Sorry for the digression though. Do not worry about "too much pressure." What you'd ideally like to do - an exercise with some tedium -- would pressurized the entire case and force the pressurized air at highest velocity through narrow apertures over the hottest mobo, RAM, CPU and VRM parts for immediate exhaustion from the case.

So for that, with my Skylake (de-lid CLU re-lidded) running neck-and-neck with various 240 and 280mm radiator water-systems, or actually better -- in one case, by 7C @ 4.7 Ghz.

Cutting Lexan and gluing it is tedium. Even cutting foam art board and glueing it is tedium. I have Xacto saw-blades. Nice to have tiny clamps for these projects, and I've used two or three different specialty glues to build my "interior doll-houses."

Good thing I don't yet have arthritis. Well -- leaving off. Gotta play the St. Laurent and Cote D'Azur stock-car roads in GRID2 with the Mach 1 Turbo Mustang, maybe knock off the Scottish countryside circuit in my Lotus in Assetto Corsa.

Nervous habit.
 

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