I have a KFA2 GTX780Ti with what looks like an Nvidia Titan style cooler. I want to create a slightly positive air flow in my case but need to know what the air flow out due to the graphics card will be. Can't find this info anywhere, any ideas or estimates?

Have no idea what your asking - can you post pics or something

My graphics card cooler looks like this which looks like the Nvidia reference Titan style cooler. It sucks air from inside the case and vents it out of the case through the graphics card. I want to know what the flow rate, or peak flow rate, of the fan in the cooler is so that I can compensate when choosing case fans.

 

E.g. I have a small 80mm fan that vents out of the case behind the motherboard and even that has a flow rate of about 20CFM, so I think the graphics card fan would be more. I'm considering up to 6 case fans with flow rates around 70 - 80CFM and want to maintain perhaps ~20CFM positive net flow. So I think the graphics card fan would have an impact.

 

But what is the flow rate of that coolers fan???

Your over thinking this thats a contained fan system in your gpu will have no effect on case fans - just add your case fans and and then control your gpu fan with a software - usually crank up gpu fan while flight simming and turn it down during normal use - I always have my case fans on full 

I think I understand what Djang0 is getting at.  I've been down the road of graphics card coolers that draw outside air into the computer case and those that draw air from inside the case and vent it outside.  If your computer case lacks intake fans, then a GPU cooler that sucks air from outside the case is a real good idea.  But, these days, most cases have multiple intake fans and the fans tend to be larger in diameter than the ones in old computer cases.  With multiple intake fans, a GPU cooler than draws air from inside the case and vents it outside the case should be just fine.

E.g. here's one possibility for my CoolermasterCM690 II case:

Intake = 200CFM

Enermax 120mm Twister Storm = 73CFM (min)

Enermax 140mm T.B. Silence = 81CFM

Enermax 90mm T.B. Silence = 46CFM

Exhaust = (176 + ??)CFM

Enermax 120mmTwister Storm = 73CFM (min)

Enermax 140mm T.B. Silence = 81CFM

Panasonic 80mm Panaflo = 22CFM

KFA2 GTX78Ti cooler CFM = ??

 

What is the air flow out of the case due to that graphics cooler?

In that confined pc case just do what I stated and you will be fine