I just bought a couple of EVGA 2080TI refurb blower cards. I need to run them in a Workstation where the PCIe x16 are 2-slots apart, unlike the gaming motherboards with 3 or 4 slot spacing. 
 
The EVGA cards have a thicker plastic shroud around the blower than some of the other brands and the metal backplate, which effectively closes the gap so one card has hard time getting enough air. 
 
I'm thinking to remove the metal back plate from one card so the other one next to it can draw more air. 
 
If I have to move one back to the PCIe x8, the 2080 TI Founders cards seem actually to do better, other than blowing their heat all over the place. 
 
I need them for GPU compute. 
 

This is my motherboard layout. It is a Xeon workstation, and like many professional boards, the graphics slots are spaced 2-slot format. 
 
In my case, slot 2 and 3 are my x16-lane slots. The others slots are x8. The bottom slot has an Infiniband card in it.  
 
While it might not seem like a lot of difference, having both cards in x16 lane slots turns a 6 day computing run into a 5 day computing run. 
 

 
 
This is what I need to accomplish. Well, with the 2080ti cards, rather than the Quadro RTX8000 that I wish I could afford. Two of those RTX8000 would set me back $11,000. I have to get by with what I can afford. 
 

Definitely try running as is just to see what your temps are. 
Depending on your configuration its very well possible that you will be 
fine temperature-wise even with the tiny gap in between. 

can you put a card in slot 1 and in slot 4?
 
 

aka_STEVE_b
Leave the side panel off your case and place a fan blowing at them is the coolest & cheapest option.

This also works

So here are the actual photos of the chassis, with the cards where I need them to be. The gap between the ridge around the blower and the backplate of the next card is 0.681mm, measured with a feeler gauge. That's like putting your hand over a vacuum cleaner. It can't get any air. 
 
 
 
 

 

Why haven't you taken the backplate off yet and told us the difference in temperature?  Why are you avoiding finding the answer?
Backplate on second card vs no backplate on second card: let us know your result.
 
Regarding the x8 vs x16, the difference is probably very small.  Certainly very small compared to the thermal throttling you are currently witnessing within few minutes -- according to you.  So, sacrificing x8 instead of x16 in the grand scheme of things seems like a no-brainer.
x8 not throttling vs x16 and throttling: let us know your result.

Adding a backplate used to be a modification.  Now taking a backplate off is a modification?  Wow, times have changed.
 
How many hours or days are you losing due to throttling?  I still believe that x8 without throttling will vastly outperform x16 with throttling.  Your workload should be GPU intensive, right?  I mean, that is why you are using GPU compute, right?  This isn't a PCI-E bandwidth intensive workload, right?  I mean, if it were, you would just be doing the computations on the CPU and avoid using PCI-E at all.  Catch my drift?  PCI-E bandwidth may have an effect, but it should have a small effect compared to the GPU computation power that you are losing due to throttling.
 
If the PCI-E bandwidth has more of an effect than the GPU throttling, I have to believe that you have vastly overstated the severity of the throttling that you have witnessed.

Years ago I had the same issue with no air flow. I inserted the rubber PCI protectors of the cards in-between the two cards at the rear corners to open the gap. There is plenty of give to open the area and the difference was measurable.
 
You could place something similar in-between your cards near the smallest space separating them by 3/8 of an inch easily. Add an external fan blowing across the cards would help as well.
 
 

If anyone else is contemplating stacking two of these side by side, get a different blower card. If you're going to run just one, then it is a perfectly great card. I can imagine in a tight small format case, it would be very good actually. 
 
But not two in 2-slot spacing. Buy another brand of blower card. 
 
I pulled the backplate from one card and it helped quite a bit with cooling and airflow. It is usable now and gets sufficient air. 
 
This card is constructed pretty weirdly, unlike all the other blower cards out there. EVGA definitely did their own thing with the cooler and baseplate. The backplate cannot simply be removed by itself. The plastic top shroud has to come off first, then one of the screws in the backplate is held in by a nut on the chip side of the circuit board, where it would normally be screwed into the base plate of the cooler. But - it is a blind hole, so it is attached with a nut. So when you unscrew it, it just spins. But the top comes off. 
 
Also - the screws are too long, owing the the 2.5mm high offsets screw bosses cast into the backplate. So I had to round up some washers and spacers. 
 
If it is desired to re-assemble with the backplate, it goes onto the PCB first, and the screw and nut on the top of the PCB. Then the main cooler chamber and 4-spring screws with the VRAM heat spreader, then the upper shroud and the remainder of the backplate screws and the PCI fence and screws. 
 
It is a a little out there. Great as a single card or with 3-or-4 slot wide spacing (but the double fan cards are quieter). 
 
A slight change in the design of the plastic upper shroud and the backplate to allow adequate clearance for airflow would have been easy and made them more versatile.