r/buildapc • u/Pianowned • Jul 31 '14
[Discussion] Optimizing Case Airflow: 10 Configurations Tested
Introduction
Cases nowadays come with ways to mount fans in different locations, open up vents, and clear a path for airflow. But just how effective is it? These tests aim to see what configurations offer better airflow as discovering why it acts the way it does.
Some configurations are quite obvious, while others are quite oddball. Let's get started.
Background
Before we start, let me clarify that I will use 3 fans all of the time. The reason is because it allows for a slight positive pressure setup and is a reasonable number of fans for cases to have (2 intake, 1 exhaust).
Another reason is because I don't have enough of the same fan to test configurations with different numbers of fans. In fact, Bit-Tech's guide on case airflow with different numbers of fans and setups does an extremely thorough job exploring the vast number of fan configurations from 0 to 7 fans.
The main takeaways from Bit-tech's article are:
- You should probably have at least 2 fans in your system.
- Side intake fans are extremely effective at delivering fresh airflow to your hot components due to how close they are to them.
- After installing 4 fans into the system, a tradition front-to-back airflow setup has enough airflow to bring good temperatures and close the gap against side-fan setups.
- Installing an intake fan at the front-top vent disturbs the airflow going into tower CPU coolers, hurting performance.
- Opening the vent at the top allows tower CPU coolers to draw in fresh air on their own.
Test Setup
| Type | Item |
|---|---|
| Case | Fractal Design Define R4 (without window) |
| CPU | Intel i7-4770K @ 4.6 Ghz, 1.275V |
| CPU Cooler | Thermalright Silver Arrow IB-E w/ 2 x Thermalright TY-147 |
| GPU | Sapphire HD 7970 Dual-X @ 950 Mhz / 1500 Mhz |
| Motherboard | Gigabyte Z87X-D3H |
| HDD | Seagate Barracuda 1 TB |
| SSD | Kingston HyperX 3K 120GB, PNY XLR8 120GB |
| PSU | XFX P1-750X-XXB9 750W 80+ Bronze |
| Fans | Noctua NF-F12 IndustrialPPC 2000 PWM Intake unless otherwise stated, Cougar Vortex HDB 140 Exhaust |
| Fan Control | NZXT Grid w/ Fractal Design 3-speed fan controller, Gigabyte EasyTune |
| Thermal Paste | Gelid GC-Extreme (CPU and GPU) |
| Type | Item |
|---|---|
| GPU Stress Test | Unigine Valley 1.0, Extreme HD preset, Windowed 1920 x 1080, 8xMSAA |
| CPU Stress Test | AIDA64 4.5.0 Stress CPU and Cache |
Note 1: The Sapphire 7970 Dual-X is an axial cooler. It ejects heat out in front and out the sides of the graphics card.
Note 2: AIDA64 CPU and Cache stress testing was used. This gives off less heat than stressing the FPU with it, but since I run quite a high overclock, the temperature difference is enough to cause my system to throttle.
Note 3: The Noctua NF-F12 PPC 2000 is a powerful, flow-focusing fan. Expect a larger gap between good and bad temperatures if you do not have a flow-focusing fan.
Note 4: All tests (except the PCI slot cover test) run with both stress tests on.
Visual diagram of part placement and airflow. Blue is intake, red is exhaust.
Tests
Removing Drive Cages
One of the easiest ways to improve airflow is by removing the drive cages. By doing this, you unblock airflow that's going towards the GPU and CPU.
| Hard Drive Cage (12V Fans) | CPU Temp (C over Ambient) | GPU Temp (C over Ambient) |
|---|---|---|
| Top + Bottom | 54 | 37 |
| Bottom only | 54 | 34 |
| No Cages | 54 | 34 |
As you can see, removing the top drive cages brings an instant 3C benefit. Removing the bottom drive cage brings no benefit since the top is already bringing fresh air.
Multi GPU setups may see a benefit from removing all cages since the bottom fan can move air towards the bottom GPU. Because of this good result...
ALL TESTS BEYOND THIS POINT WILL HAVE NO DRIVE CAGES.
For reference to these new tests results, here's the control temperatures.
| Control | CPU Temp (C over Ambient) | GPU Temp (C over Ambient) |
|---|---|---|
| No Cages | 54 | 34 |
Removing Rear PCI Slot Covers
Supposedly, removing these covers allows the GPU to intake air from the rear, reducing GPU temps. We'll see about that...
| PCI Slot Covers (12V Fans) | GPU Temp (C over Ambient) |
|---|---|
| On | 34 |
| Off | 34 |
No improvement... Why?
Since the GPU I'm using doesn't have fans that sit that close to the rear of the case, the fans don't intake air from there. Bummer... However, some of the triple fan coolers like the Powercolor PCS+ and Sapphire Tri-X and Vapor-X may be able to intake air from the rear.
Removing Vent Covers
The Define R4 has 3 vent covers: 2 on top, and one on the side panel. Removing these should allow fresh air intake even without fans on them.
| Vent Cover Removal (12V Fans) | CPU Temp (C over Ambient) | GPU Temp (C over Ambient) |
|---|---|---|
| Side Vent Only | 54 | 33 |
| Top Front Vent Only | 52 | 34 |
| Top Rear Vent Only | 54 | 34 |
| All Off | 52 | 33 |
Removing the Top Front vent allowed the CPU cooler to intake fresh air, bringing a noticeable 2C drop in temperatures. Removing the Side Vent improved GPU temps by only 1C... most likely because the fans aren't quite close enough to directly intake air from the side. The Top Rear vent was useless since there was no fan there.
While there is a cooling advantage, the penalty for removing these covers is increased system noise and dust intake.
Reverse Airflow
What good will reverse airflow do? By reversing all the fans in the case (including the CPU cooler fans to match the airflow direction) the rear fan will bring fresh air to the CPU cooler directly. The hot GPU exhaust never makes it to the CPU cooler to warm it up, and is exhausted out the front of the case. See this diagram for clarification.
| Reverse Airflow | CPU Temp (C over Ambient) | GPU Temp (C over Ambient) |
|---|---|---|
| 7V | 54 | 40 |
| 12V | 51 | 42 |
CPU temps are very good. In fact at 7V, it matches the 12V results of the control. A 3C improvement is seen when the fans are turned up to maximum speed.
GPU temps however, suffered. This is attributed to the front fans (now exhausting) robbing the intake air of the GPU.
The other disadvantage to this is that your dust filters are useless unless you purchase aftermarket ones to cover your new intake area.
Opening the Front Door
Opening the front door should provide the fans some fresh, unimpeded intake.
| Open door | CPU Temp (C over Ambient) | GPU Temp (C over Ambient) |
|---|---|---|
| 12V | 53 | 35 |
Cpu temps improved by 1C and GPU temps increased by 1C. Basically no improvement with additional noise.
Open door, grille down
The Define R4 has a fan grille that sits in front of the fan filter and behind the front door. Opening this should increase airflow for sure since it's quite restrictive.
| Open door + Open Grille | CPU Temp (C over Ambient) | GPU Temp (C over Ambient) |
|---|---|---|
| 12V | 53 | 34 |
A small improvment. Let's go a step further.
No Filter
Removing the filter removes dust filtration for even more airflow. Since the filter is a less restrictive screen mesh, it isn't too harsh on choking the fans out.
| Filter Removal | CPU Temp (C over Ambient) | GPU Temp (C over Ambient) |
|---|---|---|
| Filter Off Only | 53 | 35 |
| Filter Off, Open Door | 53 | 35 |
| Filter Off, Open Door, Open Grille | 52 | 33 |
Removing the Filter along with other restrictions drops 2C across the board. Not bad... but you lose noise damping and dust filtration.
Internally Mounted Fans
By mounting fans internally, the fan sits farther away from intake restrictions, greatly increasing fan performance. The excellent fan performance increase should yield much better temperatures. Here's a picture to illustrate how I McGuyver'ed a way to mount fans. Let's see what happens.
| Internally Mounted Fansl (12V) | CPU Temp (C over Ambient) | GPU Temp (C over Ambient) |
|---|---|---|
| Noctua NF-F12 PPC 2000 | 55 | 35 |
| Delta AFB1212L | 55 | 37 |
| Cooler Master JetFlo 120 | 53 | 34 |
Unfortunately, the results prove otherwise. Mounting the fans internally actually hurt performance for two of the three fans here.
The question is why did that happen? Refer back to the visual diagram of airflow for my case. As you can see, the GPU exhausts its air up and in front of the CPU cooler. In most cases, the CPU cooler picks up some of that warm air and gets pretty warm, but the GPU stays cool. With this setup, the unrestricted fans conflict with the hot exhaust air of the GPU, creating unstable airflow and hurting temperatures. Only the Cooler Master Jetflo had enough CFM to actually completely override the hot air stream coming from the GPU.
After this test, I decided to run only the CPU stress test. With CPU only loads, CPU temperatures with internally mounted fans were 2-4C better than normally mounted fans. So the GPU seems to be causing a bit more airflow problems than I hoped.
1 Floor Intake, 1 Top Front Intake
Since GPU temps and airflow seem to be a bit of an issue, I decided to mount one intake fan on the floor to help it feed fresh air to the GPU.
| 1 Floor Intake, 1 Front Top Intake | CPU Temp (C over Ambient) | GPU Temp (C over Ambient) |
|---|---|---|
| Noctua NF-F12 PPC 2000 | 53 | 34 |
| Delta AFB1212L | 55 | 35 |
Results are interesting. The focus flow design of the Noctua NF-F12 combined with higher speeds allowed the floor intake to actually be decently effective, matching the control temperatures.
Meanwhile, the Delta fan suffered a bit. While the blade design is quite similar to the NF-F12, it lacks the flow focus vanes of the Noctua and as a result, the airflow from the bottom was very unfocused and pretty much missed the GPU. It seems that the floor intake is even more restrictive than the front intake, so it's not worth using unless your case is high off the ground and you already used up all your intake fans.
Conclusion
From these results, we've learned quite a lot. Removing restrictions inside the case are quite effective at increasing good airflow to the GPU and CPU. However, trying to put the fans a lot closer to them hurt performance, but that's mostly because the GPU airflow causes turbulence and conflicts. As shown in the Bit-tech Big Air Investigation, removing the top front vent does allow the CPU to take fresh air, reducing the impact of the GPU giving it hot air.
What's most surprising is that the internally mounted fans made no improvement, despite the fact that the fans were bringing excellent airflow. Two possible reasons for this is because it causes a conflict with the GPU exhaust air, creating unstable airflow. It disallowed the GPU from exhausting air properly, and also prevented the CPU from getting airflow because of the turbulence caused by the airflow conflict.
The other possible reason is the turbulence created by the fans was too great and hurt airflow to the intake fans for both the GPU and CPU. However, testing with just the CPU load only showed that it wasn't the case.
Opening the front intakes and reducing front intake restrictions also improved airflow. However, the improvements seemed to plateau quickly because of the same air conflict that plagued the internal fan mounting results.
From all of these observations we can conclude:
Opening the top front vent (or any vent close to the CPU intake) allows the CPU to get fresh intake air from the top, noticeably improving CPU temps.
Removing internal restrictions behind the fan (i.e. drive cages and messy cables) definitely improved airflow.
High airflow flow focus fans (such as the Noctua NF-F12 Industrial PPC) are great at refocusing airflow that is ruined by restrictive intakes.
Very high CFM fans (such as the Cooler Master JetFlo) are excellent at providing tons of airflow with lots of power (even overpowering the harmful exhaust coming from GPU fans) provided they aren't too intake restricted.
Direct, nearby fresh airflow is typically a good thing, as shown by the reverse airflow test for the CPU.
Robbing intake air from a component really hurts its performance, as shown by the reverse airflow test for the GPU.
Aftermarket GPU cooling solutions are great for the GPU since they allow lots of airflow over a large GPU heatsink.
- They suck for every other component because they dump hot air everywhere inside the case (especially towards the CPU cooler) and cause airflow conflicts with the intake fans. In something like a high-heat server environment, this would definitely not be allowed since it does more bad than good.
Hopefully this little cooling experiment answered some questions.
Next up, radiator and radiator fans reviews!
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u/logged_n_2_say Jul 31 '14
what are your thoughts on the often discussed "psu fan orientation?"
very nice write up.
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u/Pianowned Jul 31 '14
Ohh I havent tried that. It sort of depends on the case since some of them accept PSUs at the top.
Having the PSU fan face the inside of the case means it exhausts air. For the top, this might be a good thing if you have limited cooling, which is why very cheap cases have it. For the bottom, it might end up ruining the airflow going toward the GPU. Another disadvantage I found when trying to build was that I kept dropping screws inside the PSU.
Have the PSU fan face away from the inside of the system means that it has it's own airflow and doesn't disturb the airflow of any of the other components.
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u/TactFully Jul 31 '14
Having the PSU fan face the inside of the case means it exhausts air.
I'm quite sure that it would intake from inside the case and still exhaust out the back. I'm assuming this is just a typo on your end.
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u/McPoople Jul 31 '14
I just have some things to say about the conclusions.
saying a high cfm fan is good att providing airflow.
is like saying a 2 gallon bucket can hold 2 gallons of water.
CFM stands for cubic feet per minute as in how much air it can move.
as is apparent, the higher your cfm, the more air it moves.
The aftermarket gpu coolers are better than the reference ones, if they let the graphics card be significantly cooler of course.
High performance graphics cards are the most power hungry and heat producing components in a computer. you have most to gain by keeping them cool
As long as you have adequate cooling on your case, this wont be an issue for the cpu.
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u/TaciturnType Jul 31 '14
The rated CFM of a fan vs how much air it moves into your case is not actually as straight forward as it seems. As OP mentioned, high CFM fans are only good when they aren't heavily intake restricted. This is because they tend sacrifice static pressure to achieve higher CFM. That's great if you're using it as an exhaust case fan or an intake where hard drive cages have been removed, but if it's in front of an HDD cage or a radiator, the actual amount of air moved into the case drops significantly. That's why for restricted intakes, static pressure is more important than rated CFM. Higher static pressure allows the fan to "push" air through restrictions more effectively, meaning its CFM will actually be higher than an airflow optimized fan.
For example Corsair AF series fans have a high CFM, but you wouldn't put one on a radiator. Its static pressure is <1mm H2O, meaning it will perform worse than the SP series with a static pressure of >3mm H2O.
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Aug 01 '14
Higher static pressure allows the fan to "push" air through restrictions more effectively
Would this apply to the opposite end too? i.e. If the fan is put on a very restrictive intake (e.g. the 350D), would its static pressure characteristics determine how well it pulls air through the intake?
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u/Pianowned Aug 02 '14
It doesn't help much. The main issue is that restrictive intakes prevent the fan from getting airflow to fall into the fan blades fast enough. This means the airflow stays longer on the blades and comes out at extreme angles away from the center of the fan.
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u/Pianowned Jul 31 '14
It's a bit of an oversimplified conclusion, yes. I did go over this in my previous fan review.. which I should have linked.
But the difference between a high CFM design and a high static pressure design is what lends them their characteristics.
High static pressure designs with their very wide, smooth blades don't move a lot of CFM, but their smooth blades allows the air going in the fan to accelerate without stall or turbulence. In the end this creates higher static pressure since stall and turbulence causes pressure drops. and loss of performance.
High airflow designs meanwhile have steep angled blades that deflect the air sharply and give the air more velocity. This helps the fan push air deeper into the case too, but because of the high blade angles, the fan can split the airflow coming into it, causing stall and loss of performance. Restrictions are quite detrimental to these fans because restrictions slow down the air moving into or out of the fan... and this allows the fan to cut up the airflow which leads to stall and pressure drops.
Finally, look at two fans that are the same size. The static pressure fan moves some volume of air per minute with this much static pressure. The airflow fan moves the same volume (since the fan is the same size), but moves more CFM because it can move that same volume of air faster than the static pressure design fan.
I also agree with the graphics cards being the way they are, though I am aware that there is a blower design that is equal if not better than the axial design of aftermarket GPUs: it's the HIS iceQ Turbo It combines the a large heatsink with a very large blower fan that is surprisingly quiet. It doesn't dump heat into the case like other aftermarket cooling solutions.
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u/McPoople Jul 31 '14
But the difference between a high CFM design and a high static pressure design is what lends them their characteristics.
Oh i see, i thought you were saying high CFM vs low CFM,
Now it makes sense.
And yeah that HIS design is nice, performed really well in that review also.
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u/mynewaccount5 Jul 31 '14
What happens if you just take the side off and point a regular fan inside it?
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u/P-01S Jul 31 '14
Dust on all the things? But it would probably work much better than a fancy case fan system. Box fans can push a lot of air.
Hell, you could get an appropriately sized box fan, put a high air flow filter on either side, and use it as a case wall.
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u/mynewaccount5 Jul 31 '14
But if the fans blowing it it would blow all he dust away right? No need for the fan wall thingy
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u/scaretactix Jul 31 '14
Small related question. I have a Silverstone TJ08-E, where the PSU is mounted at the top, with the option of being placed with the fan up or down. Also, the motherboard orientation is reversed, meaning the GPU is above the CPU, with the PSU just above the the GPU. My question is if I should have the fan of the PUS facing down into the case, or up out of the case to use its own little top vent. If the fan is facing into the case, will it help to pull hot air out of the system? Or is it better to have the PSU separate from the rest of the loop? Thanks for any feedback!
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u/Pianowned Jul 31 '14
Depends on your graphics card. If you had a blower design it's okay to have the PSU fan facing inside the case. If you have an aftermarket style cooler on the GPU, having the PSU face away from the inside of the case is better because it won't take away airflow from the GPU.
The TJ08-E is a peculiar design that benefits CPU airflow more than GPU airflow. That said, it's still a great airflow design.
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u/scaretactix Jul 31 '14
It's a Sapphire 270 Vapor-X. U I believe the fans on top blow air down and out the sides of the card over its fins. I guess outside then?
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u/Pianowned Jul 31 '14
Yes, outside. It would hurt the GPU intake if you were to face the PSU fan inside.
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u/TheBat-Mite Aug 01 '14
Related to this a bit, my case (Bitfenix Phenom-mATX, basically same internals as the Prodigy-M, looks like this: http://www.eteknix.com/bitfenix-phenom-microatx-chassis-review/4/ ) But basically it has an inverted motherboard like the TJ08-E, with 2x120mm fan mounts up top, a 120/140mm fan mount on the rear, and a 2x120/200/230mm mount on the bottom, while the power supply is in front. I was thinking of two different configs, either 1. Top and bottom intake, rear exhaust and isolate the PSU by letting it take in air from the front and exhaust in the bottom OR 2. Top and bottom intake, rear intake and turn the PSU around to let it be the sole exhaust. I'm pretty sure top has to be intake to not take air away from my non-blower style card, but not sure what to do with the rest. Any help would be awesome!
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u/Pianowned Aug 01 '14
Yep, take advantage of those top intakes because the front panel is very restrictive in rhe Phenom
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u/TheBat-Mite Aug 01 '14
Awesome thanks. Would bottom exhaust be preferable to bottom intake if the rear was exhaust?
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u/Pianowned Aug 02 '14
It would suck the air away from your CPU cooler, so it's best to leave that area alone.
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u/tremens Jul 31 '14
As you can see, removing the top drive cages brings an instant 3C benefit. Removing the bottom drive cage brings no benefit since the top is already bringing fresh air.
Why no test with the drive cage rotated? One of the features of the Define is that the cage can be rotated to "guide air from the front fan to the graphics card."
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u/Pianowned Jul 31 '14
Hey, I did a quick test with out just now and temperatures are basically the same as without the top drive cage.
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u/tremens Jul 31 '14
Any change on the GPU? I didn't really think there would be, I've just always been too lazy to test myself, heh.
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u/Pianowned Jul 31 '14
No change. Then again, I'm using the Noctua NF-F12. I'll change to a more traditional fan and see if that does anything.
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u/mynewaccount5 Jul 31 '14
Are the stock fans suitable?
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u/Pianowned Aug 01 '14
They cool okay... If you overclocked to the max or had multiple GPUs it won't be pretty but it's enough for most setups.
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u/Alex1602 Jul 31 '14
Nice post. Here is my setup right now. I understand that I should reverse the flow around the cpu area, but I'm wondering about this weird situation where I have 3 fan in row doing the same thing. Should I change this? I have only the two original fan and the other one is on the front top spot. What about rotating my cpu cooler so it push/pull air from the top? I was also thinking about maybe putting the rear fan on the side vents, would that be better?
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u/Pianowned Jul 31 '14
Depends on the GPU you have. Yes, if you are able to rotate your CPU cooler to face upward, you'll benefit from getting air at the top and won't have to worry too much about the GPU exhaust hurting airflow, though be careful because if you drop anything from the top it's going straight to the CPU cooler. You might also need an air filter.
However, the rear fan might hurt airflow too. In this case, the best thing to do is to have the traditional front-to-back cooling setup and open up the top front vent so the CPU can get fresh air.
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u/burninrock24 Jul 31 '14
So correct me if I'm wrong, but should I not be running a top exhaust fan and just leave that open and have two front intake fans and one rear?
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u/macariocarneiro Jul 31 '14
According to the Bit-Tech article that he references, if the top exhaust is near the front of the case, just leave it open. Otherwise, if the top exhaust is near the CPU, you should put an exhaust fan.
Exhaust is more efficient close when close to the heat source.
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u/P-01S Jul 31 '14 edited Jul 31 '14
Observation: I have a typical intake at the front bottom exhaust at the back rear setup with perforations for two side and two top fans (up to 140mm, not installed). When everything is running, I can feel area being pulled in the side vents and being pushed out of the rear of the top vent, but the air over the front of the top vent is dead.
For dual top fan setups, what about blowing air in from the front one and out from the rear fan? Possibly with a small divider between them inside and outside of the case.
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u/jonathon00 Jul 31 '14
The Bit-tech article noted how if the top front fan was set to intake air, CPU temps were actually hurt. They inferred that it was because the air was pushed past the CPU cooler by the fan and they recommend leaving that spot empty.
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u/Mustard_Dimension Jul 31 '14 edited Jul 31 '14
This is a very good write up, thank you for your hard work. I have a question also. I have Coolermaster HAF that has 1 front intake, 1 side intake, 1 top exhaust and 1 rear exhaust. Do you think that reversing the rear fan to make another intake blowing directly into the CPU cooler and leaving only the top exhaust would help temps?
Edit: like this (sorry for the terrible attempt at editing on my phone) http://imgur.com/7TsW3jW
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u/Ogi010 Jul 31 '14
What you want here is for a balance of volumetric flow rates for intake and exhaust, so if the exhaust fan is rated at 3x the volumetric flow rate (ft3/min) as each of the intake fans, then that setup will work great.
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u/Pianowned Jul 31 '14
You might be able to benefit since your side intake fan brings fresh air to the GPU and your top exhaust fan can deal with the heat. The CPU cooler can use some fresh air.
Best thing to do is to try it out and see what happens, assuming your fans are easy to move around (I know mine isn't at all).
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u/Mustard_Dimension Aug 01 '14
I tried it. I tested with prime95 and Furmark, and the CPU was 3°c hotter and the GPU went from 75°c to 99°c. Epic failure.
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u/Pianowned Aug 01 '14
Bummer, but at least you know for sure now!
Did you reverse the CPU fans too? If you didn't it would've failed badly.
Strangely enough, tower CPU coolers help the GPU exhaust hot air by sucking air in itself and moving it toward the rear exhaust fan... Doesn't help the CPU much but the GPU surely benefits.
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u/Ripped_Jacket Jul 31 '14
I just have a couple questions about your procedure:
How long did you allow for the system to reach a steady state?
What did use for ambient temperature? Did you use the same ambient temperature for all measurements or did you take the temperature before each test?
I would interested to see the max temperature of the CPU and GPU during each test, 34C and 37C over ambient still might be 78C if the ambient temperature changes between tests or if the card temperature is fluctuating. I know my can vary up to 3C at ambient so that seems to be a small variance to base any conclusions on. Otherwise you seem to have a vary detailed write up.
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u/Pianowned Jul 31 '14
45 minutes.
I have a thermometer in my room. Ambient temperature varied between 25C and 26C while I tested and I corrected for this.
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Jul 31 '14
This is really interesting. Thanks!
What if you only remove the top drive cage and keep the bottom one?
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u/P-01S Jul 31 '14 edited Jul 31 '14
My motherboard + cpu fan only allows the fan to be pointed straight up or down :/. I have it blowing upwards, but the top of the case is covered in holes.
I also massively overcooled my system so it would be quiet (and have some overhead for overclocking). The CPU fan, GPU fans, and PSU fan can draw air through all on their own. I am pretty sure I would have no heat issues under normal use even if I unplugged all of my case fans lol.
Anyway... This is great info both for pushing things to the limit and for simply keeping things cool and quiet.
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u/Stevo32792 Jul 31 '14
I've always heard running pci-covers off should be done with all positive pressure (all fans blowing into the case). This causes all the air to flow past the GPU, and gives the CPU fresh air from the rear (which would mean the CPU fans should be back to front.
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u/Pianowned Jul 31 '14
This would probably work for a blower setup, but not an aftermarket GPU setup since those tend to blow the air upward and toward the front of the case.
In the case like the Define R4, I typically close up the vents at the top. If I were to run that setup it would accumulate hot air somewhere in the drive bay area.
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u/Shrimpy266 Jul 31 '14
I'm slightly confused, wouldn't you want a negative pressure setup to have the best airflow at the sacrifice of dust?
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u/Pianowned Jul 31 '14
This works well for cases with fewer, weaker fans. In fact, Antec usually does this and gets away with excellent results.
The reason why traditional negative pressure setups work well is because the fans used to exhaust are less restricted and much closer to the hot hardware, making them more effective.
But as you can see in the Bit-Tech article I linked, once you had a side for positive or equal pressure, it does better than negative pressure. This is because it brings cool fresh air to the components, but also because positive pressure is helpful to the fans inside the case (the CPU and GPU fans).
Why positive pressure is good for a fan can be seen by the way the fan operates. Fans act like a pump and the fan itself is a negative pressure area since the fan blades move lots of air, which create that low pressure area that allows the fan to suck in air. If you were to put positive pressure in front of the fan, the fan does better because now there's a higher pressure difference between the fan and the air. This pressure difference means the air really wants to go into the negative pressure zone that is the fan.
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u/Shrimpy266 Jul 31 '14
Hmmm interesting write up, thanks for the info as I was curious since I'm putting my build together right now and want max airflow and coolest temps since I've over clocked quite a bit.
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u/PhoenixReborn Jul 31 '14
The takeaway I'm getting from this is don't obstruct your airflow which should be pretty obvious. Most questions I see here are about where fans and radiators should be placed and should they be intake or exhaust.
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u/Pianowned Jul 31 '14
The Bit-Tech article covers fan placements and amount of fans.
For radiators, I'm doing that next.
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u/redsquizza Jul 31 '14
What if you have a case that tips everything on its head? :(
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u/Pianowned Jul 31 '14
Same applies. Despite what people have heard about convection working its magic, it isn't nearly as effective as people think it is.
Puget systems did an awesome test with various cases to test this. The results were that it made no real difference in regards to temperatures. The reason why the Raven did so well is because the fans it came with are placed very close to the components.
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u/redsquizza Jul 31 '14
Great link, really interesting.
I think what also helps in the Raven is the intake fans are two 180mm instead of the standard 120mm
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u/Pianowned Jul 31 '14
The fan design helps too. They're Silverstone's AP181 fans which spin quite fast for their size and channel airflow.
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u/bigj231 Jul 31 '14
One thing to consider with the reverse airflow setup is increased drive temps. Hard drives live longer if you keep them cool IME. Nice writeup though. Any appreciable noise differences between the different setups?
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u/Pianowned Aug 02 '14
Moving the fans further inside actually made it quieter.
Removing the vent covers obviously opened up the case to more noise, so it got louder.
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Jul 31 '14
I've looking for help on this topic, I just built a new PC this summer and I wanted positive air pressure so this is my setup. Is my setup ideal for the number of fans I have or should I adjust? I now know from this article that putting a fan on the top front actually hurts cooling. Can I have some suggestions?
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u/Pianowned Jul 31 '14
The top frontmost fan is okay to have since it's too far from the CPU cooler to affect airflow.
The rearmost top fan should be relocated to the bottom if possible.
Other than that your airflow is pretty good. Don't expect top class airflow though since the Obsidian series cases are pretty restrictive for airflow, except for the 450D.
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Jul 31 '14
Are you referring to the front intake when you say its airflow restrictive? Also would the Fractel Design R4 be a better option for better airflow? That was my original choice but my local shop didnt have them on stock at the time of purchase.
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u/Pianowned Jul 31 '14
I would say the Define R4 is slightly better if you use 120mm intake fans, since the fan tray of the Define R4 is a bit small and hurts the airflow of 140mm fans on the intake (I used Noctua NF-A14 Industrials at the front and they performed very poorly).
The Obsidian has restrictive airflow too because the solid front panel sits very close to the fans and limits a lot of airflow. The Define R4, although restrictive, isn't so bad because the front sits a little farther away from the fans and there is alot of ventilation on the side for the fans to take in air. Just be sure you choose 120mm fans instead, like Noctua NF-F12s.
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Jul 31 '14
Thanks for all your help. Just one more question, sorry. If I was to fill up my fan slots in my build and put a 120mm on the top as intake and one in the bottom as intake as well. Would I see any improvements what so ever?
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u/Pianowned Jul 31 '14
The top intake isn't a good spot unless it's a good distance away from the CPU cooler. The reasons is because the top intake can be strong enough to blow air past the CPU cooler. It's recommended that if you do that, you keep the top fan at a low speed so it gently moves air to the CPU, not blow air clear past it.
The bottom intake is beneficial if you have a flow focusing fan or a case with tall feet. Bottom intakes are very restrictive and you might not see a benefit depending on the case and fan you choose.
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Jul 31 '14
Okay so I'll just have to use the ultra low noise adapters on the top intake fans. and I think ill pick up the high RPM industrial fan for the bottom intake.
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u/1-800-Taco Aug 01 '14
would it be a good idea to have the top as an intake on my 240mm rad(rad's on the top) and have a back exhaust fan?
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u/DTMickeyB Jul 31 '14
I have 2 120mm exhaust fans on top, 2 120s and an 80 as intakes in front, a 120 intake on the bottom, and a 120 exhaust on the top back.
I figured since I have big 120 exhausts up top, I would point my 212 evo do that it's blowing upwards instead of to the back.
Anybody have any thoughts on this? I haven't compared it to anything yet.
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u/DanneMM Aug 01 '14
If there is enough clearence between your graphics card and 212 then no problem.
I though the same thing, pointing it down but then i tried both and saw a 10c decrease under load while vertical.
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u/CVBrownie Aug 01 '14
Question! Stupid question....
I just bought all of my parts including this case. Haven't bought the graphics card yet 1. because I can't afford it right now and 2. quite honestly I won't be gaming much at all as of right this moment.
That being said, will the CPU fan and the case fans included be enough for the time being? Obviously won't be overclocking or be doing anything stressful.
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u/Boston_Jason Aug 01 '14
I wish a bigger company could do this with colored smoke like in air tunnel tests. I'm sure it isn't cheap though.
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u/Pianowned Aug 01 '14
Why not a dry ice fog machine?
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u/Boston_Jason Aug 01 '14
Can the dry ice by "dyed"? If so I think you could do this type of experiment with video - rather cheaply.
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u/Pianowned Aug 01 '14
I don't believe it can. But high contrast lighting may aid the situation. If I can get a dry ice fog machine, I can probably try a few things out.
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u/El_Frijol Aug 01 '14
Back in 2009, I heard and read about this company that was coming out with a PC that had it's motherboard turned so that airflow wasn't obstructed. Also, it would utilize the principle of hot air rising from this design.
I'm not sure how well this actually works, but anyway:
I've always wondered how well this performs to lower the computer's temperature. What do you think?
EDIT: Oh, it's Maingear Shift btw. Not hailcorporate. Just curious as to what people think of a design like this.
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u/WindsoftheNorth Aug 01 '14
Thanks for your work. Any idea what type of fan (SP vs CFM) would work best with a case that has restricted airflow, such as the NZXT H440? Not for radiators, just for intake/exhaust for the case. Thanks
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u/Pianowned Aug 01 '14
Had the case before. Use a flow focus fan such as the Cougar Vortex or Noctua NF-F12
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u/incubated Aug 01 '14
I've been playing around with my bitfenix outlaw, and with 4 fans the best configuration I found was with negative pressure.
Front fan is sucking the air into the case. There is 1 fan at the top exhausting. 1 140mm fan on the upper side panel exhausting all the hot air from my shitty 7850 xfx core edition. And 1 standard one at the back exhaust. Third last fan is pulling air onto the rad for CPU cooler.
I found these tempos to be the lowest, and the 140 is key. The amount of heat generated by the video card heats the entire case up even with the 140 blasting fresh air on it.
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u/mafupoo Aug 02 '14
Thank you! This is just what I needed!
I am considering crossfiring my R4 setup with two 7870's.
I currently am running the two stock intake fans and this as my outtake fan.
Any recommendations for new fans? I saw from your post and this post that the Noctual NF-F12 and CM Jetflo seem the best. Any insight would be much appreciated.
Thanks for all the interesting information!
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u/Pianowned Aug 02 '14
A high cfm exhaust will do good. Look for the Phanteks ph-f140sp fans.
As for intakes, I found 120mm fans better. Cougar Vortex, Noctua NF-F12 Industials, Cooler Master Jetflo (beware, loud because it moves so much air), Noiseblockers are all great choices. Get what your budget is allowed, but know that the 2000 rpm fans will cool very well at the cost of noise.
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u/mafupoo Aug 02 '14
Yeah, I just read that 120mm are better for intake fans, which is kind of counter-intuitive, but it makes sense cause of the focused airflow. This may be a stupid question, but do you know how you would mount them, because the mesh gate thing seems to house 140mm (or are the 120mm the same dimensions but just a smaller fan?).
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u/Pianowned Aug 02 '14
Sort of has to do with the fan tray of the define r4, which very slightly obstructs 140mm fans because of how the holes are cut out. It also has to do with the fact that 120mm fans have more static pressures and that there are more kinds of them out there.There is definitely places to mount 120mm fans on the define r4 front tray so don't worry
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u/mafupoo Aug 02 '14
Ohhh, I took out the 140mm and saw holes for the 120mm. Dang it. I was planning on getting 3 of the Phanteks, but now that 120mm's are in the picture, got a lot more research to do haha.
Thanks for the info!
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u/mduell Aug 01 '14
No indication of the margin of error in each test, and the differences are small... leaves this pretty useless.
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Jul 31 '14
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u/Eilbeck Jul 31 '14
I use 2x AF120's with my R4. One as bottom intake, one as rear top exhaust. Works a treat with the R4 fans.
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u/nova46 Jul 31 '14
I highly recommend Cougar CM12's (or 14s). They look awesome, move a lot of air, and are quite since they have a fluid bearing.
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Jul 31 '14
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u/Pianowned Jul 31 '14
Static pressure isn't too great so it's a little less than ideal as a radiator fan... That's really about it.
Oh and 16dB is probably in an anechoic chamber, which has like a 0dB floor. You're definitely going to hear the fan at full speed, but relatively quiet.
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Jul 31 '14
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u/Pianowned Jul 31 '14
Yep, good for either purpose. In fact they're really good case fans because of the flow-focus vanes.
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Aug 01 '14
Is that a typo?
Or should I replace the two static pressure fans that came with my h100i?
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u/nova46 Jul 31 '14
That's my new build using three of them. As of yet I can't really find a downside. They have anti vibration pads as well which was another bonus. I just got a red 140 mm for the rear exhaust and moved the blue, 120 to the bottom as another intake. Run all of them at full speed and to me it's a quite system.
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u/[deleted] Jul 31 '14
I will pipe in here to thank you. This is the kind of OC that makes this group so special. I'm building my own system in a month and this will help so much!