80mm Exhaust and 120mm Intake

Nov 7, 2018
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I got this generic casing with only 2 fans installed. At first it was 80mm intake and 80mm exhaust. The 80mm intake got damaged so I had to replace it with 120mm because that's what I have from my old chassis. So my question is, would this affect airflow? Given that my air intake is much larger than the air that the 80mm can push out.

I watched one video from Linus just now when he was unboxing one of their orders $1500 pc. The fans on it were unequally size and he got worried. Now that I saw him worried, makes me more worried.

Would this unequal fan size give me trouble?
 

Darkbreeze

Titan
Moderator
Yes. Same for the back fan too if there is room. If you have room to drill holes that are similar in size to those that are already there, until the circumference of the grillwork is the same as that of a 120mm fan, then you can add a larger fan back there as well. That would be a very good idea because honestly the fans inside the power supply do not tend to move much air out of the case plus the power supply would enjoy a longer life if it didn't have to use hot air to cool itself.
 

Darkbreeze

Titan
Moderator
Linus is an idiot. Period.

As far as your fan configuration is concerned, that is a very minimal cooling configuration however increasing the size of one of the fans cannot "hurt" anything. Yes, it MIGHT create a positive pressure arrangement, but that will ONLY cause you to have better dust suppression. It's not going to reduce your cooling capability at all. It might actually increase it since an older case with only room for an 80mm exhaust fan will probably have many gaps and holes for air to escape from so some amount of the added air pressure is going to find it's way out, taking some heat with it.

Optimally, you would want equal air pressure or negative air pressure for the best cooling. As follows.

High static pressure fans are desirable for all intake fans, radiator fans or heatsink fans. All of those types of fans will usually encounter significant resistance to airflow, so having fans with higher static pressure is desirable in those applications.

Exhaust fans do not face much resistance, so using fans with high static pressure is not necessary in those locations, however, USING them will not hurt anything either. Technically, you generally want fans with the highest CFM and highest static pressure you can reasonably afford to purchase for intakes, heatsinks or radiators. Exhaust fans, the static pressure is not very important but high airflow (CFM) is generally desirable.

For most configurations 2 x120mm, 2 x140mm or some combination of the two for both intake and exhaust are sufficient. WHEN possible, using a 140mm fan is much preferred as you are able to move an equivalent amount of air as a 120mm fan at a lower RPM resulting in a lower overal noise level.

Negative pressure configurations offer the BEST cooling performance. Positive pressure configurations offer dust suppression. Neutral pressure, with an equal, or nearly equal amount of airflow coming in as what is going out, offers a good solution that meets both types halfway. This is the MOST recommended configuration. If you want the best cooling performance, then you might not only add another exhaust fan to that top rear position like I said, but make sure it is a high CFM model AND also maybe replace the current rear exhaust fan with a model that has a higher CFM rating as well.

BeQuiet fans are only good in regard to noise levels, and that is only because they tend to run their fans at a maximum RPM that is significantly lower than most other comparably sized fans. They are good for systems that don't need great cooling and silence is more important, although you can technically do that with any fan by adjusting the fan curve in the bios and capping it at a speed that is acceptable.

If performance is more important, I would stick to fans by Noctua (And yes, they have black models now so you are not stuck with baby poop brown), Thermalright (Not to be confused with Thermaltake) or even possibly the EVGA FX 140 or 120m fans which move a lot of air but are a bit noisier than these others. Corsair Maglev fans are also fairly good.

However, in your case, with an older chassis that only has an 80mm exhaust, if you cannot install a 120mm fan in that (hopefully) rear exhaust position, then there's not much you can do. I'm guessing this is probably a case with a top mounted power supply, or no? What IS your case model?

What are the rest of your hardware specs?
 
Nov 7, 2018
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Dang, I learned a lot in just a span of 4 minutes. Thanks man.
Yup, you got it right, the psu is top mounted. It's an $8 Fortress generic casing. I was planning to change the exhaust to 120mm too but the slot is only good for 80mm. the 120mm intake is placed on the side panel.
 

Darkbreeze

Titan
Moderator
Ok, so I know you don't want to hear this but there's two ways of looking at this and neither of them are very good IMO.

One, you need a better case. What country are you in? I can probably source you a really decent case, at least much better than what you have, for around 35 bucks. Maybe less than that if you're in a country that has local versions of Craigslist. Anyhow it's an option IF it's an option monetarily, meaning, if your wallet agrees.

The other option is that maybe you mod your case. There are a lot of tutorials and youtube videos on modifying a case for a larger fan. Most of them are primarily for cases with bottom mounted power supplies though. The fact that you have a top mounted power supply means that in reality you actually probably have TWO 80mm fans or an 80mm and a 120mm fan, both actually at least somewhat as exhaust fans.

So that side 120mm fan, IF the fan grill up front is large enough to accomodate the entire circumference of the fan blades, is definitely not causing you problems. It would be a lot better if you had any front fan locations or could mod the case to accept one. I've done this many times to a number of cases, but I may have tools and experience you lack so it's understandable if that's something you don't feel comfortable pursuing. Let me just link you to this to give you some ideas though about modifying the rear fan location for a bigger fan or adding a front fan location.


I don't get into detail, you can find that elsewhere, but if you look through the whole thread you'll see how I enlarged the rear fan location that originally only supported a 120mm fan, to be able to handle a 140mm fan, and I ADDED another fan in front where they used to be only optical and hard drive bays.


http://www.tomshardware.com/forum/id-2528266/140mm-rear-exhaust-storm-enforcer.html

 
Nov 7, 2018
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yeah, I'm much more interested in modifying this case. I love modifying. I wanted this generic case to look good before I sell this for a better price.
My old specs are:
amd a8 7600,
emaxx a70fm20+ mobo,
1x8gb ram,
1 hdd,
deepcool fan with the blue fan(cheap one)

Modding the front of the case is a pretty good idea. There's an 80mm fan slot there inside, but the external part is fully covered. I think modding will also include drilling tiny holes until it covers 120mm hole to the front side of the case would work? is that right?
 

Darkbreeze

Titan
Moderator
Yes. Same for the back fan too if there is room. If you have room to drill holes that are similar in size to those that are already there, until the circumference of the grillwork is the same as that of a 120mm fan, then you can add a larger fan back there as well. That would be a very good idea because honestly the fans inside the power supply do not tend to move much air out of the case plus the power supply would enjoy a longer life if it didn't have to use hot air to cool itself.
 
Nov 7, 2018
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When I checked the back, I don't think I can extend the circumference to 120mm. the slot for the io shield is just right beside the 80mm. Below the 80mm is also the slots where cards will come out. above the 80mm is the power supply slot. I just realized, this is one ugly looking case. lol. I was thinking drilling holes at the top for exhaust. Its somehow has decent space for 120mm. Will there be issues, If I'm going to do it at the roof of the case?
 

Darkbreeze

Titan
Moderator
Not much point really in a top mounted fan in FRONT of the power supply. Can't hurt I guess but those old style case designs were just not intended for use with modern hardware. A fan there is likely to simply move the air path away from the CPU and motherboard where you want it to be and bypass that area altogether.

Can you post some pictures of that case? I've worked some pretty crappy cases into really good mods in the past. Might even be able to move the fan sideways and put another 80mm fan next to it. IDK, without seeing the case it's hard to say.

What FAN MODEL is being used in the 80mm fan location?
 
Nov 7, 2018
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honestly, I don't know the model, it's a generic one too that came with the case. Here's the pic of the case. https://www.facebook.com/pcrigobsessionphilippines/photos/a.2237157796528611/2261133224131068/?type=3&theater

 

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