Originally Posted by
93MARKIII
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....
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.