Potentially dumb question but have you checked to make sure your truck didnt already come with both and e-fan and a mech fan, i know some dont but alot did. The stock efan is hooked up to the ac and kicks on when the pump cycles for "extra cooling", but if you have a tuner like sct or diablo you can tell the computer what temp youd like to have your e-fan come on at with out having to run any extra switches or sensors. 3.0 guys are also dropping their mech fans and running just the e-fan from duratec's so a factory fan can definitely handle the work load.
My truck came with both and i have removed the mech fan and left just the e-fan, i also dont have a tuner so i watch my temp gauge and my hvac switch now also doubles as my fan switch. The temp gauge has never moved higher then normal, its been in cold fogginess and sat in 110* LA traffic always runs at a consistent temp with no worry of over heating. The radiator is designed to cool a 4.0 v6 and i think thats the main reason it runs so consistently, its a huge radiator to run on a focus motor.
Parasitic loss? throttle response? more of teh sw33t MPGz? I dont track my miles and ive never been to a dyno so i dont know. I personally didnt notice to much of a difference only thing i noticed for sure was the revs drop slightly quicker after the iac valve is done hanging the revs. Am i still glad its gone? absolutely since for me it was a free mod and those are always the best kind. Would i pay 150 to do it? probably would just cause im a honda guy and the thought of a mech fan on a 4cyl bothers me but i wouldnt expect a ferrari after im done.
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