Thread: added UD pulley's, need to change anything?
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Old Mon, June 15th, 2009, 06:17 PM
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Originally Posted by Sburn View Post
Thank you. I claim no special abilities other than I enjoy reading wiring diagrams and powertrain manuals and such.




I can make a guess why Ford ended up with such an elaborate system: R-134 refrigerant in the A/C just doesn't work as good as the older R-12 at idle/slow speeds, so you really need the fan to be engaged and pulling fresh air through the condenser when the vehicle is moving slowly. But, at highway speeds, the fan doesn't even need to be there at all to provide A/C and engine cooling and becomes a load that hurts mileage. Being that the PCM already knows the vehicle speed, ambient temp, A/C status, engine temp, etc. anyway, it makes sense to spend a few extra bucks for some wires, connectors, and a few lines of CPU code to eliminate the above two issues. And since it's all just softwre at that point, might as well do something smarter than just On/Off controll and have the PCM map the perfect fan RPM against temps, A/C, VSS, engine temps, etc.. And after replacing one or two of the older visco/thermo -style clutches in my time, I can see how having the PCM know about a misbehaving clutch would be a good thing.
Oh, I think you're being a bit modest. You seem to understand and make inferences from what you read too. Not everyone can do that.

The part I "bolded" in your quote seems to make a case against e-fans, doesn't it? An intelligent fan that puts little to no drag on the engine at highway speed, but that runs (through a direct couple) when the engine is at idle to keep everything cool. Some people forget that the power for e-fans HAS to come from somewhere, and that "somewhere" is the alternator that is powered by the engine. Anytime you increase the load on the alternator, you MUST increase drag on the engine. And, since there is a "middleman", sort of, in this system (the alternator), you cannot have 100% transference of power to the fans, since nothing is 100% efficient.

And, to the th3godf4th3r (and everyone else), sorry that I hijacked this thread. It's one of my great failings. :o

- Jack
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