I'm wording if i wanted to run SLI on my pc , With my power supply located on the bottom of the pc case with the PSU fan sitting right next to the second video card . Would this cause a problem with overheating the GPU on the video card. In other words the PSU is pulling air in and the pushing it out the back of the pc case. Now the video card is taking air in from the pc and pushing it onto the GPU. So ultimately their is only a inch or two between the PSU and the GPU.
I'm not quite sure what you're asking. Do you want to know if you can use SLI? To answer that, we need to know the motherboard and PSU. Or are you asking how the air flow will work? If that's the question, here's the answer:
The cool air will be pushed in by the front fans and pulled in through the side mesh (or pushed by an additional fan there). The exhaust fans (PSU, the top and back fans) will pull the cool air over the cards, where the GPU's heatsink and fan will cool the card. The now hot air will be pulled out of the case by the exhaust fans.
If you're asking if the air flowing through the PSU is going to case the GPU fans to be stressed, the answer is no because the fans orientations are different. The PSU fan moves the air perpendicular from the bottom of the case, while the GPU fans move it parallel to the bottom. The two systems don't cause extra stress on the fans that way.
GPU cooling works exactly the same way in SLI as it does if you only have one card.