New G5 build - Two 80mm fans or One 92mm Fan at rear end ?

[macnb]

Just starting out on a G5 build.
Going to be using a Lian Li motherboard tray, back plate and I/O Panel from a sacrifice case I mentioned here.

For the rear exhaust fan, I was going to use 120mm fan. It will fit if I don't mount the motherboard tray on the existing G5 stand-offs.
But I plan to use the stand-offs to aid cable management (i.e. hide them under the tray).

So, having made the decision NOT to use a 120mm fan at the rear,
I am now looking for feedback as what to use: two 80mm fans or one 92mm fan ?

They will be Be-Quiet fans most likely.

The back-plate will eventually be flush mounted to the case with JB-Weld.
To practice this welding, I have "prepared" the back-plate by "filling" in the 120mm fan holes and it's mounting holes with scrap pieces cut to size:



Here it is after JB-welding and plenty of elbow-grease to smooth it out before applying primer:


BTW, this was the first I ever used JB-Weld and it's amazing stuff. I left it curing for 30 hours sat next to a hot radiator in the house.
Very strong and grinds down very very smooth with p800 sand paper.
(I took lots of photos for the build log later).

I did some quick mock ups of fan options and how the backplate would be cut to size.
First option is to use the existing G5 dual fan grills behind two 80mm holes:

Second option is to use dual 80mm fans with standard grills:

Third option is one of the existing G5 dual fan grills behind with one 92mm fan:

Apart from the aesthetics of two 80mm vs one 92mm fan, there are efficiency aspect to consider in terms of airflow.
Can I assume 2 x 24 CFM 80mm fans are better than one 34 CFM 92mm fan ?

What do the expert modders recommend - two 80mm or one 92mm fan ?

 

[Dschijn]

It depends on the Hardware you are going to use. If you realy need the cooling go for 2x80mm.

 

[macnb]

It depends on the Hardware you are going to use. If you realy need the cooling go for 2x80mm.

Thx Dschijn.
H/W: GA-Z77X-UP5 OC 4.7Ghz, 16GB Vengence RAM, Corsair H100i CPU watercooler, Intel HD graphics but may add a graphics card later, Samsung SSD and will add a 2.5 WD Black HDD.

May be better to add 2 80mm to insure for an NVIDIA GPU card later ?

 

[neilhart]

Quote ... What do the expert modders recommend - two 80mm or one 92mm fan ? ... /Quote

If you work at it, you can run a 120 mm fan at the rear. I did it on the Short Stack:
.

.
And in the early test version of the Short Stack, I had a Thermaltake Water 2.0 Performer closed loop all in one liquid CPU cooler installed on this fan port. I found that the liquid CPU cooler was over kill and went with an air CPU cooler (this is with a non-OCed i7-3770K).

However in your case it all depends upon where and how you mount the Corsair H100i CPU water cooler and the rest of the conversion detail.

Good modding,
neil

 

[macnb]

Quote ... What do the expert modders recommend - two 80mm or one 92mm fan ? ... /QuoteIf you work at it, you can run a 120 mm fan at the rear. I did it on the Short Stack:

Thx neilhart. I remember tracking your work on the Short Stack - amazing engineering.

I can fit a 120mm fan but with a compromise. That is, I would have to drop the mother board tray by 7-8mm (by not mounting it on the existing stand-offs).That would mean that I cannot hide the power, sata, etc cables under the tray as there would be no room.

Alternative is to NOT use the tray at all and mount the motherboard directly onto the chassis leaving enough room under the motherboard for hiding the cables (by using the 16mm G5 standoffs).

Regarding the H100i, I have narrowed down two positions.
First option is vertically at the front (as intake):


Second option is on the floor of the case (as exhaust with additional intake fans on the front):



Current favourite is to exhaust on the floor as that leaves good room at the front to mount the HDD bay (under the DVD shelf).