Originally posted by Tony M:
I don't agree with that. The power loss is because of the hp required to turn the mechanical fan. The alternator is already being turned at all times, so the electrical draw from a electric fan will not put any additional mechanical drain on the engine.
Since removing the mechanical fan lessens the hp drain caused by friction, there will be a net gain.
Tony, you need to head on up to Folsom and visit the old Folsom Power House. Among other things, they have a deonstration setup wherein you hand-crank a generator and then add load to it. You will discover the generator gets darn hard to turn pretty quick!
It's not just the fact that you are spinning the generator. It resists spinning in proportion to the load on it - more load, more resistance to turning.
So, roughly speaking, it's the same load whether it's a mechancal fan or an electric one.
BUT: those old stovebolts have pretty crude fan blades; whereas most electric ones I've seen have more aerodynamic-looking blades. So it's possible there's a gain from the improved aero efficiency.
OTOH, the electric fan has two energy-conversion (mechanical to electric, electric back to mechanical) inefficiencies working against it.
All it all, it's mice nuts on an old truck. Correct tire pressure makes *way* more difference.
Cheers!
George
