I've got an initial chart done for EDFs and it looks like I've made my choice on the motor/EDF combo. The two with the most thrust on a 3 cell and under 40 amps are the 2.5" 64mm 7 blade EDF running on the 3900 k/v HXT2835 motor (about 25 ounces of thrust) at around 30 to 35 amps, or the 2.68" 68mm 5 blade EDF running on the 3900 k/v HXT2835 motor (about 23 ounces of thrust) at around 26 to 33 amps. These are rough averages on the compiled data I've dug up from users.
The 2.68" with this motor, while producing slightly less thrust than the 2.5", is more in the EDF's rated thrust range (750-950g), while the 2.5" is rated to handle 400 to 1500g. That leans me a little more toward the 2.68" even though it may have slightly less thrust with that motor, but what closes the deal for me is that there were more examples of the above thrust and amps to be found on the net to help verify those numbers than the 2.5". For that reason I'm opting for the 2.68" unit being powered by the HXT2835 3900 k/v motor. It would be interesting to see some further tests on both of these fans done with this motor to see which wins out. Anybody?
Update since this post: I bought both fan units so I'm the one who gets to compare them both with the 2835 3900 k/v motor.
Incidently, check out some of the user remarks on United Hobbies website about this inrunner. A few guys are throwing it on Strykers (as pushers, not with the EDF) and reporting some very nice air speeds. At $17 for this motor it's a winner compared to the brand names it "mimics".
The next size up EDF (3") had some examples for its, but most if not all of those were for 4 cell or higher packs.
I'm also wondering about the shaft diameter of the EDF and the motor. Some say 3mm, some say 3.175mm. Some say they changed it on the EDF. Fairly confusing. Guess I'll just pick up the 3 and 3.175mm adaptors to cover all bets.
It should also be noted that the HXT2835 (the non-heat sinked version that you should be buying for an EDF) will fit the 2.5" fan but it's .2mm bigger, so the motor's case needs sanded down or the EDF mount hole expanded but people have done it. Think I read where a guy just grinded off a few little plastic ribs in the EDF mount hole to make the motor easily fit. The 2.68" fan has a 29mm mount hole so a little tape wrapped around the motor should snug it just fine according to one post.
23 to 25 ounces of thrust on an EDF using a 3 cell lipo is a little better than I expected to find for them. I can see myself building a nice little fast platform that may indeed do unlimited V still. [8D] Here's the chart I compiled with more to add later. Sorry about the format as the web can/has screwed it up some times. Also sorry I didn't edit down some of the rant at the top. Didn't feel like it doing that yet. It was more of a "mission statement" for myself to focus on what the chart was going to be about.
http://www.rcgroups.com/forums/showthread.php?t=822677