Hello Everyone,
After install the Hybrid Cooler on my SLI of 1080 FTW, the temperatures changed as follows:
Top GPU: 53 load; (33 idle)
Bottom GPU: 58 load; (38 idle)
 
Before install the Hybrid Kit:
Top GPU: 82 load; (50 idle)
Bottom GPU: 72 load; (48 idle)
 
As you can see, before the installation, the top card always run 8-10 ºC hotter than the bottom card (under load). Now, after the installation the bottom card always run 5º C hotter than the top card (idle and under load). I double checked it.
 
I didn't inverted the cards to test yet.
The load temperatures were tested using 10 minutes of Unigine Heaven.
As the temperature gap is always 5º C, even at idle, I don't think it could be the radiators location.
 
Do you think is it normal the bottom cards gets hotther? Is it worth to disassenbly the cards and change the thermal paste? (I used the pre-installed thermal paste).
 
Thanks in advance for your help,
Cheers!
 
-------------------------------------------
Update on 02/21/2017
-------------------------------------------
New radiators position setup and new tests done. I added the new image at the initial post.
Ambient temperature: about 31 ºC
Run 10 minutes of Unigine Valley.
I got the numbers using the Precision software.
 
Top GPU:
49 ºC (32 idle)
Voltage: 1.000 V (0.625 idle)
 
Bottom GPU:
54 ºC (35 idle)
Voltage: 1.063 V (0.625 idle)
Power: always 3% - 7% higher than the Top GPU during load
 
The 5ºC gap remains the same. Could be the Voltage?
Although this fan configuration seems strange, it is very efficient and the internal components of the case look very cool.
On the Hybrid Kits, I touched the tubes and radiators during the tests, and they get extremely hot. Much more than the CPU AIO. It seems to be a good idea to use them as exhaust fans and prevent the tubes from getting too close to each other.
Now I don't know if worth it the disassembly process, in order to change the thermal paste. Any ideas?
Cheers!
 

Scarlet-Tech
I would definitely disassemble and change the tmermal paste, just to make sure it gets good coverage. I would think both cards would run abkut the same under hybrid coolers, especially if the coolers are both exhausting.

You picture isnt showing right now, just ahows a broken image link. Your picture is set to private on google, so only people that know you may be able to view it. Set your image to public, or use imgur to upload a picture.

Are you able to see the picture now?
 

 
Ok, sorry about that.
Image attached now.
 

Thanks for your reply!
I have tried to to install the radiator on the fan at the front top, and invert the bottom as intake. No difference on GPUs temperatures at all, but the CPU rad get much hotter.
 

Before you start stripping the cards down, you might want to experiment with the fan/radiator placements.  It is possible there is a mild contact problem, but your load temps are only slightly high and more importantly the idle/load delta is the same between the two cards.  The odds on creating a perfectly replicated contact problem on both cards is low.  
 
In fact, a 20C delta isn't bad all.  However, your idle temps on both are high, unless you are in midst of Summer in warm room.  My 120 radiator kit is mounted in the rear exhaust and like you the CPU radiator is set as top exhaust.  The GPU idle temp is lowest in the system, sitting right at room temperature.  What kind of room and case temperatures do you have?
 
With the lower #2 GPU using intake air from the front, I would expect it to be cooler under load, however since it is both warmer at idle and load, I wonder if there is a different issue.  Can you compare the two voltages on your cards (idle and load)?  The two Asus 980's I recently removed were quite different.  One original ran at the standard 1.20v for that model, but the thrice RMA'd card only needed 1.06v to make its mark.  It was always cooler than 1.20v, no matter the position.
 
In the front panel, highest slot, the GPU radiator will dump waste heat into the CPU radiator.  That is likely the reason for the higher CPU temps.

Thanks for your reply!
Yes, it is Summer and my room is pretty warm (about 33ºC). That is the reason i changed to the Hybrid solution.
Definitely I will invert the cards and check the voltages before the disassembly process. I will post here the results. Thanks for the tips!
Just for note, I updated the BIOS containing the new fan curve (thermalmod) and currently it is setted to the SLAVE bios.
 

 
I would move the Front Radiator Up 1.
This way your Bottom Front Fan will pull in cool fresh air into the Blowers on the GPUs.
Between the two GPUs is where you need it the most to cool the VRM and even the PCB.
This also puts the Bottom of the Radiator above the GPU as Recommend.

Thanks!
But on the FTW Hybrid Kit, the fan on the cards exhausts hot air. It is not the same type as on the non FTW kit.
 

X-TAC
Perhaps, but you don't need a lot of air on the hybrid models.  The GPU fan is cooling the VRM and memory modules and he hasn't mentioned an issue with those.  It won't have any effect on the diode temperature cited above.  Either way, the on board GPU fan is displacing the air around those board components.  Moving that air out, rather than the actual temperature of the replacement air, is what makes it effective.   

The (memory modules) are cooled mostly by the Radiator not the Blower Fan on the FTW Hybrid Cooler.
 

Also the Blower Coolers Exhausts Hot Air out the Rear of the Case unlike the ACX Coolers.

Nice looking Rig mmuna
 
My basic airflow test --> if you see the temps decrease with the side cover to the PC Case removed, there is room for improved airflow.
 
I also agree that you should look at the voltage and see if the warmer card has a reason to be warmer.

New radiators position setup and new tests done. I added the new image at the initial post.
Ambient temperature: about 31 ºC
Run 10 minutes of Unigine Valley.
I got the numbers using the Precision software.
 
Top GPU:
49 ºC (32 idle)
Voltage: 1.000 V (0.625 idle)
 
Bottom GPU:
54 ºC (35 idle)
Voltage: 1.063 V (0.625 idle)
Power: always 3% - 7% higher than the Top GPU during load
 
The 5ºC gap remains the same. Could be the Voltage?
Although this fan configuration seems strange, it is very efficient and the internal components of the case look very cool.
On the Hybrid Kits, I touched the tubes and radiators during the tests, and they get extremely hot. Much more than the CPU AIO. It seems to be a good idea to use them as exhaust fans and prevent the tubes from getting too close to each other.
Now I don't know if worth it the disassembly process, in order to change the thermal paste. Any ideas?
Cheers!

mmuna
Thanks for share your build SKRYKER, it looks awesome!
ksgnow2010 -> it would be great see an image of your build!  :-)

Here's an infra-red picture...I'll have to take a regular picture and post it!
 

Oh, reverse flow.  That's interesting.  I was just wondering how that would work out if I put a 360 on the front and 280 up top, both as exhaust with bottom/rear intake.  You'll need to adjust for any room temperature differences, but since the idle/load delta came down 1/3C respectively, that does look like an improvement.  However, since most people's liquid temps are so much lower than air cooling, a 1-3C difference might not be overly compelling if you have to make sacrifices elsewhere.  I would think this would be better case and component temperatures as well since all the waste heat is now going straight out, but I have not tried to run in reverse.  I would take off the front air filter, if you haven't already done so.  The 740 has a pretty good one with a little offset from the frame so it doesn't completely choke the fans, but it is still resistance and you shouldn't need it in this configuration.  
 
It looks like you also found the voltage difference and that explains the temperature gap between the two cards.  From what I have seen, the 1.06v is normal and your 1.00v model is just a superlative example that makes its clocks with lower voltage.  Leave it where it is as the top/#1 dominant card.  It is normal the for the smaller radiator hoses to be warmer than the H100iv2.  Each of your GPUs at 100% is producing considerably more wattage than your CPU can generate, even overclocked to the brink.  To boot, it is also likely to stay at a higher load for a longer duration during gaming (or similar) whereas most people have more variable CPU loads.  Combined with the smaller volume of water in the 120mm radiator and you get a higher coolant temp than the CPU radiator.  

X-TAC
Oh, reverse flow.  That's interesting.  I was just wondering how that would work out if I put a 360 on the front and 280 up top, both as exhaust with bottom/rear intake.  You'll need to adjust for any room temperature differences, but since the idle/load delta came down 1/3C respectively, that does look like an improvement.  However, since most people's liquid temps are so much lower than air cooling, a 1-3C difference might not be overly compelling if you have to make sacrifices elsewhere.  I would think this would be better case and component temperatures as well since all the waste heat is now going straight out, but I have not tried to run in reverse.  I would take off the front air filter, if you haven't already done so.  The 740 has a pretty good one with a little offset from the frame so it doesn't completely choke the fans, but it is still resistance and you shouldn't need it in this configuration.  
 
It looks like you also found the voltage difference and that explains the temperature gap between the two cards.  From what I have seen, the 1.06v is normal and your 1.00v model is just a superlative example that makes its clocks with lower voltage.  Leave it where it is as the top/#1 dominant card.  It is normal the for the smaller radiator hoses to be warmer than the H100iv2.  Each of your GPUs at 100% is producing considerably more wattage than your CPU can generate, even overclocked to the brink.  To boot, it is also likely to stay at a higher load for a longer duration during gaming (or similar) whereas most people have more variable CPU loads.  Combined with the smaller volume of water in the 120mm radiator and you get a higher coolant temp than the CPU radiator.  

Yes, the front filter was removed. It is sad because it is a really good magnetic filter.
Now I need to find out some filters for the rear and for the bottom.
The amount of heat that come out from the front now, during stress load, is absurd! That makes me confident about this inverse setup. I really want to avoid such a heat storm geting into the case.
When I was running the tests, my office got so hot that I had to turn on a fan near the window to remove all the heat from the room!  :-)
Thanks for sharing your thoughts.