Electric cooling fan

Hi All , has anyone swapped the viscous fan for an electrical one, was thinking it would cut down on power loss from the engine, give a quieter ride etc, my fan seems noisy on start up , goes quiet after about 10 minutes, any thoughts on the idea.
TIA.

I'd thought about it. We tow a 2.5T caravan and a couple of times we've tackled hills with a broken fan coupling (fluid coupling, viscous hub, whatever you feel like calling it). I've bought a replacement coupling and it's working, I'll rebuild the old one when I get some time.

The biggest issue with electric fans is not controlling them, but getting enough air moving and dealing with how many amps they draw. I've gone back to standard wattage headlight globes (I did have 90W IPF FatBoys in but they're a waste of money) but I've increased the wattage in my driving lights (100W -> 130W each) and I have a 120W light bar, so at night when towing the caravan I have the basic (say) 20A for the car, 40A for the fridge and 40A in lights. My alternator has to supply that 100A.

I've replaced my alternator and have a 130A unit but it only develops 130A at around 3500RPM. I like to cruise somewhere around 1800-2000rpm, so my amps budget is only just being met. Easy enough to tell - voltage is staying stable above 14V, if it falls to 13.7-13.8V the alternator is struggling.

If I had to add 35-40A for a fan I'd kill the alternator.

You might not tow at the moment, or have as much light now, but adding a 25A draw for a dual battery and a 40A draw for a 500W light bar will do similar things - and if you've changed to an electric fan, you'll find the alternator coming up short.

Finally, there's an efficiency actually gained by using the mechanical fan. Converting mechanical energy to electrical (alternator) has some losses involved (equates directly to wasted engine power). Converting electrical energy back to mechanical (electric fan) has more losses.

simple problem is its difficult to get electric fans that flow enough air.
tho they have a few advantages like being able to turn them on early and to turn them off when going through water.

Yep, as above, the viscous fan is incredibly powerful, it can move A LOT of air. If you wanted to go the electric fan route, you would probably have to increase the radiator size and fit a couple of electric fans. Not a easy mod.

AU fans off a falcon move 3600 cfm. I use them on my W2A radiator. Unless you spend $$$ on some 16" comp spec SPAL's this would be your best bang for you buck option.

Only downside is they draw about 25A and sometimes up to 40A for a static start up

That must be one mother of a W2A set up youve got there - wow! Thanks for the tip on the AU Fans too. Thats hefty CFM.

Rabbid-chop said:

That must be one mother of a W2A set up youve got there - wow! Thanks for the tip on the AU Fans too. Thats hefty CFM.

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To look at it another way, ford went from the viscous hub fan in the ed falcon to thermo fans in the ef falcon. If the thermo fans couldn't flow equal or more air than the viscous fan, I can't imagine them changing for no reason.

The other advantage (possible disadvantage with the amp draw) is moving slowly. The engine revs obviously have to be fairly high for the viscous fan to move a decent amount of air. With thermos, the fan speed is obviously electronically controlled, so engine speed of the vehicle makes no difference. The disadvantage being, the amp draw of twin thermo fans with the engine running at idle. If it is clear daylight and you are not running any other electrical loads like the aircon blower fan on high speed or a winch then this may not be a big issue for short periods...

Also, on the alternator output. It would be worth checking if the rated amp output is engine rpm or alternator rpm. They are resonably ooverdriven, given the smaller pulley on the alternator compared to the crankshaft pulley. Whether you could get a smaller diameter pulley for the alternator so it runs at an even higher rpm that standard spec, you would get more amp output at lower engine rpm. The risk here is over revving the alternator and what damage that may cause.

Yeah the current draw is the big set back. Alternator upgrade would be worth looking into and an idle-up wired in. Bit finnicky. I dont think i'd bother with it on the nav, but would be interested if anyone has dimensions on the AU set up just out of curiosity. A lot cheaper than a Spal.

bods said:

To look at it another way, ford went from the viscous hub fan in the ed falcon to thermo fans in the ef falcon. If the thermo fans couldn't flow equal or more air than the viscous fan, I can't imagine them changing for no reason.

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Well... There are a whole bunch of possible reasons to upsize the alternator and maybe the radiator and go to thermo fans.

One could be to give you better flexibility for AC condensor flows when stationary, taxis...

Packaging for pedestrian crumple zone design

Some other front end accessory drive constraint like struggling to get the fan centreline low enough on the engine to get decent flows in an appropriate spot on the radiator

And it was probably none of these.

bods said:

The other advantage (possible disadvantage with the amp draw) is moving slowly. The engine revs obviously have to be fairly high for the viscous fan to move a decent amount of air. With thermos, the fan speed is obviously electronically controlled, so engine speed of the vehicle makes no difference. The disadvantage being, the amp draw of twin thermo fans with the engine running at idle.

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Well... luckily at low speed your load is fairly low; if you're at full throttle at crawling speed you're outside the envelope. So heat rejection rate isn't huge in this scenario and big speed at the fan is not usually necessary. Top tank temp on a hot day, heavy towing on a very steep grade is a good test for a new cooling set up.



Here's an oddball one; run an electric thermostat that reverses your thermo-fans on warmup, and delete your old school thermostat.

Dion said:

Well... There are a whole bunch of possible reasons to upsize the alternator and maybe the radiator and go to thermo fans.

One could be to give you better flexibility for AC condensor flows when stationary, taxis...

Packaging for pedestrian crumple zone design

Some other front end accessory drive constraint like struggling to get the fan centreline low enough on the engine to get decent flows in an appropriate spot on the radiator

And it was probably none of these.



Well... luckily at low speed your load is fairly low; if you're at full throttle at crawling speed you're outside the envelope. So heat rejection rate isn't huge in this scenario and big speed at the fan is not usually necessary. Top tank temp on a hot day, heavy towing on a very steep grade is a good test for a new cooling set up.



Here's an oddball one; run an electric thermostat that reverses your thermo-fans on warmup, and delete your old school thermostat.

Click to expand...

I was more thinking of a long slow hill climb in 4wd low first gear, without a lot of engine revs, so as to keep the speed down. Depending on terrain obviously... probably more so if you're dragging a trailer up too. It won't be an everyday occurence but still something to consider I guess haha

Gday all

Had a set of au fans on my kings wood I did up when I was a young fella. They had to be sealed well to the radiator to make all the draw come through the fins. That was done with industrial grade foam. They were switched automatically via a Davies Craig in hose thermo switch. From memory the on off temperature could be set or they sold various temperature range ones. Before I put them on the 383 would get quite hot coming through kangaroo valley. Afterwards I never had an overheating problem again. They are excellent fans when set up correctly

My 2 cents

Cheers