As you can tell by my truck vitals, I have an electric fan. I am a little skeptical of a claimed 2-3 MPG increase as a result of converting from mechanical to electrical. There is most likely a small increase but I can't say that I it was anything that was realy noticeable by itself. However, every little bit helps. The reason I did it was to improve the cooling and take the mechanical load off the engine. That in itself frees up the few HP that it takes to swing the mechanical fan for use by the drive train. However, when the fan is running it takes just about as much to run it as it takes to run the mechanical. For that reason, you want to have it come on only when the system exceeds a set temperature and not run all the time.
If you are going to put an electrical fan on, you definitely need to put one on that has a CFM rating to cool the engine properly, WHEN NEEDED. That is different for different engines. The advantage here is it will come on with full force while my engine is idling which isn't so for a mechanical fan. The main problem with stock cooling system design in general is, that it is least efficient when the engine needs it the most, (hot outside air and engine running near OR at idle speed).
I happen to be a fan
, no pun, of the Imperial 226204 control which monitors the temperture of the coolant via a probe in the radiator fins, just under neath the top radiator hose. You can adjust it for any temperature you want to maintain, mine is set to come on at 190 (5 degrees over the Tstat rating). I happen to have a super cooling system and the fan almost never comes on in the winter and on the hottest days with surface temperatures of 135+ f it comes on around 35 MPH and below, Other times it only comes on when setting at a light for 3 to 4 minutes and then goes off when I start moving.
You also need control in the cab to force it on if for some reason your sensor fails and if you are doing any off road driving, then you need to be able to turn it off when going through water that may come up to the fan level. That can be accomplished by installing an ON/OFF/ON switch in the cab.
As you can see, I use the Lincoln Mark VIII fan for a 4.6 liter engine. On vehicles with less that a 130Amp alternator it is necessary to upgrade. This fan pulls 100 amps start current and settles out at around 33 amps. That is too ******* a system with only a 95 amp alternator. An electrical system with less than 135A will most likely exhibit other undesirable problems.
A couple of pictures. 1. A schematic but mine is altered a bit, 2. The temperature probe, 3. The fan installed, 4. The original location of the controller, 5. The new location after cleaning up the engine compartment, relocating the battery, and adding a under hood fuse box to eliminate fusible links, 6. The Dash switch with an indicator under it to let me know if the fan has voltage supplied to it from the fan relay, 7. The engine it came from.
Good luck,
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PS
This is only 1/2 of the modification I plan to make to the cooling system. The other removes the Water pump and installs an electric one. That is much more significant as far as freeing up power for other usage. Perhaps I will get to it in this years projects. $-)
1/22/08
Those pictures didn't come out quite in the order I expected. This is the picture order left to right top row comment 7, 1, 6, 5; bottom row 4, 3, 2
