[yukon]

On a G4 Sawtooth, there's this punched metal backing behind the 120mm case fan, it doesn't have very large air holes. If the fan is on high, it's not pushing out even a quarter as much air as it would be outside the case and it's extremely loud because of the turbulence. Just today I've seen some odd things with G4 airflow, like air coming in from under the drives, and that metal backing seems to trap fibers really well, so I'm confused about airflow in a G4.

If you don't know what I'm talking about,
http://users.win.be/ws200167/macfun/...&power.jpg

http://www.g4noise.com/mods.php?ID=77&p=all
This person seems to think the same thing, "an adhesive film I used to cover the holes in the case. Maybe they were there for some kind of brilliant turbulence or back-pressure, but I think all they do is give the air a place to go that isn't out of the case." (note the fan flow is reversed in his MDD model, my fan is sucking air from between the metal and the plastic shell or something)

Should that metal backing be removed or reduced to lower noise and facilitate much better cooling? I don't even know why it's there as the fan's real intake appears to be at a 90 degree angle to the fan, is there something to be done to improve the intake vents? Can someone enlighten?

[Link]

The whole thing about airflow does nothing but confuse me -- at one point I did cover my g4's side with tape, but I think I eventually pulled it all off because I didn't notice any difference in volume.. shoot even the "tape over the hole in the CPU fan duct" didn't do much..

But that's possibly because the CPU fan on my g4 is loud, and I need to replace that like NOW (I think a bearing in it is going bad now), but I haven't put out the money to get that + a thermometer of sorts to make sure I don't overheat the machine in the process..

I suppose if that fan was being used as an intake there might be a difference in having those holes on the side, otherwise there isn't much of one. -- in which case taping it over would make a lot of sense.

[yukon]

Well, the G4 case is weird, it's a metal case within a plastic case, lots of holes and I'm worried that there are air channels in other areas that I'd be screwing with. I don't know where the holes behind the fan go, if it's just to a cavity in the case, then it should be taped up, if it's to some kind of other intake I don't know of then I should open it up. Either way, the fan unhappy without much intake, there was seemingly less than an inch of space between the fan and the sheet metal behind it, I need to open something up for more air.

The holes on the right side of the fan are the intake holes on the back of the case, I'd open that up more The holes that are directly behind the fan, with the case's greyish plastic siding visible through the holes, that's the problem. The honeycomb behind the fan does not appear to be taking air from anywhere, the only intake I know of is on the side of the fan (it normally looks like this)-
http://www.xlr8yourmac.com/G4ZONE/FanbktinG4.jpg

For your system, replace any 80mm fans with panaflo 80mm L1A or M1A, they're not expensive, everyone raves about them, and they've done well by me. Replace your 120mm fan with the Evercool 120mm Aluminum- it's the proper 25mm depth, it's available everywhere, it pushes a lot of air, and the chrome/aluminum look inside the case is really kicking....needs a fan controller though, 9v is good and 7v is difficult to hear. Seems you have a newer G4, from when Apple started overclocking, freaked out about heat, and stuck in like three 60mm fans, an 80mm, and a GPU fan, the Sawtooth only has 2 fans. 60mm fans are to be avoided like the plague (whiny and no airflow), 80mm can be replaced for better fans, and 120x120x25mm are available if you look (the evercool)....unfortunately the higher G4's can't use ATX PSUs, and it's unfortunate for me all the quality PC PSUs have 120mm or 2x80mm fans that would directly face sheet metal when installed...my PSU choices include a Sparkle or opening up an Enermax and disabling a 80/92mm fan (do not plug in a standard ATX PSU without proper modifications).

[Link]

Ah this is where the fun comes in okay.. if you haven't opened your machine, the side panel pops off real easy (i've done that before obviously) -- and no there's no channels there... if you've ever felt the case when the machine is running, you can feel air coming out the bottom if you don't cover the holes, but that doesn't do much good.

Opening the back up wouldn't be a bad idea, at least the metal part. As for replacing the CPU fan with a panaflo, I know that sounds great and all but they achieve the low dB at the cost of having low CFM.. aka the heatsink is going to run hotter.

My g4 is a dual 800, which does produce quite a bit of heat.. not sure how much exactly though but the heatsink is hot enough I don't want to replace the fan with anything lower power.. So far this leaves me with a Vantec thermoflow that has specs susipciously similar to the minebea that came with my g4.

http://www.newegg.com/app/ViewProduc...615&depa=0

[yukon]

Never taken the plastic off, disassembling macintosh computers to that point has always been a one way process for me, there's no way to put some of those all-in-one machines back together. If there's no air channels (and thanks), then I guess those perforations are just there to reduce pressure buildup or something, not sure how it gets clogged with dust though, when I cleaned it out I thought it must be some kind of ingenious filter.

I guess I'll open the back up if I can, just clip through some of the plastic (the metal is an EMI shield, I love Apple for taking that into consideration)....maybe use a wire fan grill....I'll see about removing some of that metal side to make room for the fan to get air.

Replacing an 80mm fan with a L1A will make it run quieter with lower CFM, yeah, but using an M1A will be quieter than standard with standard airflow, or so I'm told...Panaflo's being designed better than other fans. I don't know these systems, but if you can use an 80mm instead of a 60mm, do that fast, there are "adapters" (funnels) to change the fan, dunno if there's room in the case for it. Try to use faster large fans, and slower small fans if you can....my using a pumped up 120mm case fan, and a fan with near-L1A specs (slightly faster) in the PSU is working well. There are modification how-tos available for the higher G4s, but they were all pretty bad or simplistic, IMHO the design changes were just terrible, saw the inside of a MDD G4 today and was disgusted (dual 60mm PSU fans? an optical bay fan? CPU and GPU fans, looked like they dropped the 120mm fan. instead, rotate the sawtooth PSU the other way for two 120mm fans, and have an optical bay fan go on when the temperature raises high enough when burning). Thanks for the help, I need all the cooling improvements I can get as I upgrade.

[Link]

All in one? The powermacs are hardly all in ones..

There's no way to fit an 80mm in there without relocating the power supply.. I HAVE heard of people sticking an MDD power supply into a QS, which leaves plenty of room for a better cooling setup, but it's an expensive mod!

Myself, I think I just found what I wanted tonight muwahhaa.. A cheap 9600XT and a cheap DVI to ADC adaptor so I don't have to solder it! Yay!

[tr]

Originally posted by Link:
Ah this is where the fun comes in okay.. if you haven't opened your machine, the side panel pops off real easy (i've done that before obviously) -- and no there's no channels there... if you've ever felt the case when the machine is running, you can feel air coming out the bottom if you don't cover the holes, but that doesn't do much good.

i've felt the bottom of my case, right under where the case fan is (if looking at the sawtooth from the front, underneath the left side of the case), and air isn't coming out. air is being sucked in, well at least it is in my sawtooth. to me, it is clearly an intake (and also a place where dust gets sucked up, sticks to the holes, and often needs cleaning, as you noticed, Yukon).

so from my experience, i wouldn't cover those holes. the holes lead to an air intake channel, where air enters from the bottom, and travels in between the plastic side and the metal case.

[yukon]

The G4 isn't an all-in-one, those were just the worst of it (especially old ones, the brittle yellowed plastic snaps and it's apart forever), since that was the history and the G4 was expensive, I didn't venture farther than to take off the HS, PSU, and fan bracket

Perhaps you could fit a slim fan into your case? I'm throwing out a 80mm fan that's half the normal depth (you don't want it, it's old and has a nonstandard 4pin connector) so they exist to be fit into tight spaces. All else I could suggest would be an ATX conversion if it's possible. devise some way to take out the small PSU fans and mount a real fan externally to it perhaps....but that's just for noise, I'm doing my mods for upgradability and noise.
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Thanks tr, I couldn't check my G4. That really makes sense if it's got intake holes on the bottom, the G4 was on top of carpet for a couple months at ponts in it's lifetime, the buildup was insane....I won't cover the holes, I'll enlarge them and the area around the fan so it can get more air. If I'm not getting enough airflow, I might go further, make a stand for the G4 and cut out more area on the bottom, add a 120mm filter to the intake fan....works well for PCs, open up the front and put 2x4's under the case.

[powertrippin]

WEird. These forums are strange. Anyway, the holes you're talking about behind the 120mm fan are there for a reason. From what I can figure out, it moves air through those holes, and to the bottom of the case. There are more holes near the ends of all the hard drives....thuuusssss, pressurizing that side panel with a fan= air squirts out over all the HD's. I wouldn't cover it unless you like having hot hard drives. What we have here is a case that has a BUILT IN hard drive cooler.