Dell case horrible airflow, newb to fans, could use some ideas

ss88

Weaksauce
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Recently bought a Dell XPS 8930. I've used Dell XPS towers for many years, and have never seen such a poor design with respect to airflow. Let me introduce you to this mini oven.

To orient you, the top of pic is top of case, the right side of pic is the front of case. The case PSU is upper left,, the PSU fan exhausts to the left side of the case (toward you in pic), and intakes air from rear. The PSU is mounted to a hinging bracket (more on that later). Notice no front fans. The PC comes with the stock Intel cooler, which sounded like a vacuum cleaner under any significant load on the i7-8700 (non-K) CPU, and an exhaust fan at the top. The combined noise from these two fans under load was unbearable. I swapped out the stock cooler for the Arctic Freezer 11 LP low profile cooler (had to go low profile due to limited clearance above CPU because of the PSU). That made a big difference. Still gets a bit loud under significant load, but not as bad as before, and the CPU runs quite a bit cooler. I suspect a good portion of the fan noise is from the stock exhaust fan (connects to a 4-pin fan header on mobo, so it ramps as the CPU is loaded).
FgDfgY9.jpg


Here's a better view of the front, where I'm thinking of adding a lower front intake fan.
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Lower half of case. So I guess the idea is intake fan here brings air across to the drive bays and graphics cards, and then top rear exhaust fan pulls air up through the gap between PSU and upper half of mobo.
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You can see the path airflow would have to take to reach the exhaust fan at top rear of case:
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Here's case w/ PSU hinged out of the way:
jqeSbNl.jpg


And here's the 92mm top rear exhaust fan:
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The only airflow access via the front cover are these slots that run along both sides and bottom of front cover (there is no grill or ports on face of front cover):
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Front of chassis with front cover removed:
XgzWpn7.jpg


Lower front:
e8L1gT3.jpg


Top rear exhaust fan:
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Top rear exhaust port w/ fan removed:
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After seeing how poorly this case was designed for airflow, I might roll my own PC going forward, but since I only recently got this PC, I'd like to make it work. Mostly I want to improve the airflow situation so that the CPU runs cooler and thus the fans run quieter. And since it's 8th gen core, I'd rather not sink a lot of money into this, given that I'll probably upgrade again in a year or two. I'm thinking what this really needs is a front intake fan (maybe 120mm?) and a replacement of that 92mm exhaust fan with a 120mm fan.

A few questions:
1. Since the intake is restricted by the slots in the sides/bottom of front cover, I guess I need a "static pressure" fan directing air inward?

2. And an "airflow" fan for top rear directing air out the top of the case?

3. On the Dell forum, seems the usual route to fitting 120mm fans is to buy Alienware Aurora case fans and keep the brackets and discard the fans since the chassis is basically the same as the XPS, and the Aurora case fan brackets fit the top rear exhaust and lower front intake perfectly. These Aurora fans are ~$15 each on ebay. Seems like a waste to spend $30 for 2 brackets in which I'm going to mount different fans. Is there an alternative way to mount 120mm fans to top rear and lower front? Zip ties? Super glue? I don't mind drilling holes in the case (well out of warranty and all the ugliness would be covered by the front and top covers anyway). Suggestions? When I move on from this PC, I'd probably take any case fans with me to the next PC (which I'll probably build), reverting this PC back to stock case fan and the Arctic CPU cooler (since I view it as unusable with stock cooler).

4. Should both intake and exhaust fans be PWM or 3-pin or one of each? If the fan noise at max RPM is quite low, I don't mind it running constantly, especially if that means it would keep the CPU cooler and not require the CPU cooler fan and any other PWM fan to spool up to max RPM.

5. Suggestions on fans? I see that some 120mm Noctua fans can be had for $20 and 120mm Arctic fans can be had for $10. Would like to keep it in this price range. Seems one of the benefits of the Noctua is they package in a bunch of accessories which can make mounting the fan easier.
 
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Another idea. Maybe I could mount an "airflow" style fan to the lower front chassis and run PC w/ front cover off. I don't really care about the aesthetics; I care about the noise (constant low level noise is preferable to periodic jet engine acoustics under CPU load). And without the front cover, an "airflow" style fan could suck a huge volume of air into the case.

XgzWpn7.jpg
 
Since you have a lot of space there, I'd suggest a 30mm or so thick, high static pressure fan. That way you could run it at a lower RPM than max and still get decent airflow. The only downside would be that it may be difficult to fit in whatever case you replace this one with.

Zipties should do fine, although you may have to sand down some sharp edges to keep them from being cut.
 
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i would cut out the grill over the exhaust fan, and the front bottom intake area then put a fan there and maybe where the extra hdd caddy is, then cut out every other "tab" in the side of the face plate(or leave it off).
youll need to use a splitter off the top exhaust though.
 
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Since you have a lot of space there, I'd suggest a 30mm or so thick, high static pressure fan. That way you could run it at a lower RPM than max and still get decent airflow. The only downside would be that it may be difficult to fit in whatever case you replace this one with.

Zipties should do fine, although you may have to sand down some sharp edges to keep them from being cut.
Why only 30mm? Seems there is room for 120mm fans at exhaust and at lower front.

Cool on zipties, wasn't sure that would work. Yep, I can sand or file down sharp edges where zipties attach.
 
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i would cut out the grill over the exhaust fan, and the front bottom intake area then put a fan there and maybe where the extra hdd caddy is, then cut out every other "tab" in the side of the face plate(or leave it off).
youll need to use a splitter off the top exhaust though.
What would be the point of cutting out the grills in these areas? Just more 'clear' area for airflow? Or to make it easier to fit 120mm fans?

Rather than cut out the sides of the front cover, I'd rather just leave it off since a disfigured front cover might turn off prospective buyer when I sell this PC. Plus leaving the front cover off would allow for unrestricted air flow via a front intake fan.
 
30mm thick
Gotcha. If I go with the idea in second post to just leave front cover off, then I would go with an "airflow" fan instead of a "static pressure" fan since airflow wouldn't be obstructed? Or am I not understanding how case fans are supposed to be used?
 
yes airflow, the cutouts are crap*. if your really planning on reselling it, then just jam fans and a splitter in it and leave the face off.
*reason for sp fans
 
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yes airflow, the cutouts are crap*. if your really planning on reselling it, then just jam fans and a splitter in it and leave the face off.
*reason for sp fans
Got it. Yep, leaving face off is no problem.

For this situation, would you go with PWM fans that ramp up with the CPU load or 3-pin fans that run constantly? The exhaust fan has a 4-pin header on the mobo, so maybe I'll get a BIOS error if I don't have at least one fan plugged in there?
 
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