True. Most of the 'aftermarket' are replicated auto manufacturers designs anyway. You get some 'innovation', like that hybrid fan from Permacool which is basically a flex fan on an electric motor, which I was the most curious to test. If I didn't fear getting sued I'd publish all my fan numbers, but yeah.

When I was done testing the fans, i would sell them 'used' on craigslist, but I just threw the perma cool away.

With 'used' fans, just pay attention to the radiator thickness/density, if they are the same, they should move more in a truck. (A truck will typically have a larger opening in the grill, and present less restriction then a car front end) Taurus/mustang fans will move more in a truck, but doubtful they'll get much over 2500 cfm (which is enough). Not a fan of them because of the amp draws, but if you're not running a stereo system you don't need to worry about it.

 

so you basically jump in here and tell me im talking out of my ***, but you havent given one shred of proof against my claim that 1 inch from the rad is the sweet spot...in fact, you go into everything but that....i never got into cfms and what was advertised, anyone with any sense knows that published numbers are best case scenario...

i dont know the values, but i do know there are formulas to determine how much airflow is needed, through what material, at what density to remove a certain btu from a designated cooling fluid in a certain amount of time, why dont you publish those numbers for us since you have all this testing under your belt....

 

well it doesnt even have to be 1 inch... it has more to do with the shroud... the blades should be about half way out of it so it pulls the hot air out away from the radiator thus drawing cooler air in

:P well idk if thats the exact reason y... but i do know that it is suppose to be halfway out of the shroud... the 1 inch ur suggesting would have to fall under the tight engine compartment... and give room for the shaft that turns the fan to move in and out with out contacting the radiator...

 

Mark, I didn't intend to imply that at all, I was only trying to share my experiences. If I could have done a better job with that, my bad.

Regarding specifically the 'sweet spot', fans will work best when they are mounted at the same distance from the radiator as they were designed, which is generally as close to the radiator as can be mounted. In some cases, it might very well be an inch, but I've tested a lot of fans and that's not a perfect fit for all. They will drop off in performance dramatically as you move them farther from the radiator, so in the instance of a fan having a mount 1/2'' off, 1" isn't a great idea. (Air, like water, takes the path of least resistance and would pull from within the shroud as well as the radiator.)

Regarding my testing, again, it's a legal issue why I won't publish my results. I did not intend to sue or be sued when I started the testing, but thought it could be a division within my company. If I would have been planning for a suit, I would have done some things differently.

Finally, to address your formula's, I didn't try to engineer a fan system, which is where one would typically start with the btuh transfer forumla's. It wasn't that complicated of an issue, I simply measured what the factory fan was moving and tried to find an electric fan to do the same. I know from doing fan testing that the 3500 cfm advertised by certain manufacturers is b.s. and decided to try my own options. Specific again to the 'sweet spot', I was hoping when I started to find a single fan capable of the volumes required that wasn't such a drain on the electrical system, and was curious how different blades would react to different depths within a shroud. I didn't accomplish squat with this because the fan blades/motors are fairly weak in order to keep the amp draws low, and the fans cannot develop significant suction inlet s.p. with the additional free area gained by extra spacing from the radiator.

Early on in the project, had 'insider' conversations with 4 honest fan manufacturers and I came to the conclusion I'll never remove a manual fan for an electric in a truck. Just not enough gains to justify the price in my opinion. Continued with the testing until I realized it wouldn't be worth it from a business standpoint.

 

On the factory fans, were they driven from the engine or factory E fans? If you did get CFM from the engine driven fans, what ranges where the CFM? I doubt Ford will say anything about it as there are tons of other info out there.

 

Factory fan info I'm not worried about, and in all cases it was a mechanical clutch fan. I had an Expedition when I started this, and at idle it wouldn't pull more then 1500 cfm through the radiator. I also checked a 2001 Dodge Ram 1500 under the same conditions, and that was pretty similar. Did some tests at lower speeds, city driving under 20 mph, and 1900 cfm was a fairly common reading. Once you get over that speed, I was getting much higher airflows, but at that point the mechanical fan was kicking out and free wheeling.

Figured 2000 cfm was a safe bet for my purposes with a safety factor, and later I did find some fan manu that published some charts and it seemed to confirm that.