Dell airflow design: shroud blocks all airflow! (pictures)

[king of snake]

I'm new to silencing, been lurking here for about a month. I arrived at this site after I became totally fed up with the noise caused by my Dell XPS Gen 4. After a bit of research, I "Zalmanized" the graphics card with a VF900-CU (which cut out at least 2/3 of the noise), and I'm happy enough for the time being.

Anyway, while I was mucking around in the case looking for sources of noise, I noticed what appears to be a major problem with the airflow design. Has Dell really gone off the deep end here, or am I just missing something?

Let's take a look at some pictures...




The design consists of two fans. The lower fan is the intake, the upper fan is the outtake. Now, admittedly I'm new to all this, but it seems pretty obvious what they're going for: a circular flow that forces the air in a loop.

Now let's take a 360-degree look at that airshroud, shall we?






^ Beginning to notice anything weird?



The lower fan is totally blocked by this V-shaped piece of black plastic!



So where does the air from the lower fan go?

The only possible outlet I've found is on the side, through this tiny gap in the plastic -- which would send the air straight back towards the motherboard, BETWEEN the heatsink and the back of the case. The only thing there is a bunch of capacitors, which had gathered an insane amount of dust.




Now, either I'm totally missing something, or that V-shaped black piece was supposed to be removed at the factory. What do you think?


BTW, I bought this machine before I knew any better. I've learned the hard way that it's always better to build your own... Now I'm building my own general purpose Linux server with all quiet components, thanks to SPCR.

[Michael Sandstrom]

I was on the verge of buying a Dell three years ago but then I discovered the great Silence Savior SPCR and learned from the best. My DIY quiet rig is a pleasure to use for music and video.

[jhhoffma]

Definitely remove the plastic. I don't know if it's supposed to be there or not, but you can always superglue it back on if need be.

You could probably get by with removing the intake fan altogether and replace the exhaust fan with a quieter one. Just make sure that the air won't short-circuit around the heatsink (you may need to make a small air guide), but travel through it like your diagrams would show.

[FlorisNielssen]

My first thought was a dust filter. But a very restrictive one..
But, as you point out, it's just plastic and lots of dust is going to your motherboard, not good.
I'd remove it, don't care if somebody was supposed to do that anyway, it'll certainly help your temps and dust build up on the motherboard. The tiny gap is probably to get some of the air to the VRM's, but most to the heatsink.
By the way, those are some LARGE fans.. Like, thick. 38mm?
You could also try to lose the intake or the outtake fan by the way (if you lose the plastic cover that is). It'll probably cool the heatsink enough. What are your temps anyway?

[king of snake]

Thanks for the responses.

I disconnected the intake fan, since it wasn't doing anything anyway. I am going to remove the plastic piece too. With or without an intake fan, some fresh air coming from that intake area might help. It will still be forced through the heatsink.

I may try to replace the fans with quieter ones, but considering those fans are so thick, I'll have to make sure the new fans fit without any problems, or making the noise worse somehow.

Unfortunately, I can't check the CPU temps with SpeedFan. Must be some kind of proprietary Dell motherboard. Any suggestions? Other programs I can use?

[psiu]

Try CoreTemp. I've gotten it to get a temp on a Sempron 64 on a DFI board with Via chipset that has no thermal sensors at all--it gets the temp from the CPU itself.

[king of snake]

Well, apparently this motherboard doesn't report temps at all, because neither SpeedFan, CoreTemp, or Motherboard Monitor can produce any readings. And I found some posts from people with similar experiences online. Ah well ...

At least the heatsink is cool enough to touch after playing Half Life 2 for about an hour. Is that a good enough test?

[NeilBlanchard]

Hello,

That looks like it is a "valve"? It is a flap that will let air into the shroud, but not out.

[king of snake]

Hi Neil,

I thought so too, at first, but it doesn't move or flex at all. It's just hard, stationary plastic. There's no air getting through that thing, as far as I can tell.

[NeilBlanchard]

Hello,
It's got a 38mm thick (92mm?) fan blowing into it -- the flap will move a bit...

[king of snake]

Neil,

I removed the plastic piece today, and during the process, I found out that it really IS supposed to be a valve like you said.

However, there was some sticky stuff holding it in place, so it would NOT move to allow air through. I actually had to slide a box cutter underneath it in order to "unglue" it from the shroud.

So, this was a defective valve I guess. I removed it altogether anyway. With both fans running, and no valve, my heatsink is totally cool to the touch. Going to try it like this for a while and keep an eye on the dust. Maybe replace the fans with quieter ones.

Thanks for your help everybody. If you know anybody with an XPS, you might want to check up on this little problem for them.

[EndoSteel]

You can add a flow divider between the two fan openings for even further temp improvement. With the exaust so close to the intake, recirculation of the hot air blown out of the case is inevitable.

[nd4spdbh]

just to let you know that valve/flap of plastic is spost to be there... air is spost to come out of that smaller hole cus if you look its righ where the vregs on the mobo are. at least they were on my buddies dell that has the same setup.

[king of snake]

nd4spdbh -

Thanks for the tip, but I wonder if it's really necessary to cool the VRM's.

Isn't it true that most cases don't have any airflow directed at the VRM's? Why is Dell any different?

Or, is it because in a standard case (no shroud), the basic airflow moving throughout the entire case is enough to keep the VRM's cool...?

Any idea?

[king of snake]

Just another update in this ongoing mystery ...

I reinstalled the valve after cleaning the sticky stuff off completely, meaning that the intake fan should have no problem blowing air through the valve now.

However, being skeptical, I watched the valve through the front drive bays of my computer as it was running. The valve does not move at all. I studied it closely even as I turned the computer on and off repeatedly; it simply doesn't move.

And another thing-- even if the fan was strong enough to move the valve, the heatsink is only about 2mm away, which would block the valve from opening any further.

So essentially, what we have here is a 92x92x38mm fan at full power, blowing straight into an impenetrable wall, being forced through a 90* turn, all so it can cool the VRM's. Way to go, Dell! That can't be good for noise. (And I suppose the title of this thread was accurate after all.)

Anyway, I'm still curious if cooling the VRM's is necessary in general (see my previous post). Is VRM cooling only necessary if you're overclocking?

[seraphyn]

Never hurts to have some airflow over them, in any case. But i wouldn't worry too much about them.

[DreamKiller]

I've worked on Dell XPS 600's before, those exhaust fans should be BOTH exhausting. Someone at the factory must've installed it wrong (I've seen it on HPs too). Anyway, I say just get rid of those 92mm fans and just zip-tie a single quiet 92mm on the fan grill while the second slot is blocked (tape it up!)

[vick1000]

Remove the "valve" and make both fans exhaust.