Who is running an electric fan?

LOL

The quantifiable no feelz impact is a lighter wallet.

 

Daves assertions are indisputable. If you compare CFM to CFM, there will not be any performance gain by using an electric fan. The only way the electric fan could be more efficient is if it were able to more accurately tune the air flow to the needs of the engine minute by minute. That would also assume that the OEM fan is substantially over cooling the engine most of the time. This could be the case over the envelope where the two fans are both adequate. When the E-fan is off, it requires zero power, while the OEM fan always requires some power.

The separate question is adequacy.

 

On a performance basis there's no advantage, it takes X amount of power to move Y amount of air. That's been true since Bernoulli figured it out and physics dictates that energy must be conserved. Any difference in various efficiencies is marginal, 10% or less advantage on a per cfm basis.

The benefit is mainly when the electric fan is off it's 100% off while even brand new the viscous coupled mechanical fan is never fully off so there's a parasitic load. Since the fan on our Tacomas is unusually large based on the expected typical use, 4wd-low in Moab, towing in Phoenix, etc., that parasitic load can be significant even when the coupler is working right. When it's not then you're putting a lot of drag on the engine unnecessarily.

Plus, if you never need the full 10,000 (or whatever we assume it is) cfm then an electric fan can be a measurable improvement, save you a couple of HP and perhaps some MPG. Over time this adds up, no doubt. That's why everything built that can use an electric fan does. It's 100% or 0%, so when you need cooling you have it, when you don't want the drag you eliminate it. For road cars that have a predictable use pattern that's totally legitimate.

It should be noted that if you really don't need the full capacity you can achieve some of the same improvement using a smaller fan. Maybe one from another vehicle that's only, say, 5,000 cfm. This will also reduce the drag.

However, if you need the 10,000 cfm even just rarely then there's no escaping that you need to drag around all the extra capacity daily. In that case the ideal thing to do is two large electric fans that come on in sequence. Even on summer days commuting you probably don't need all 10,000 cfm, so a single decent sized fan is sufficient and the second only comes on when you're off road or it's exceptionally slow or hot. I'd guess that a pair of ~3,500 cfm electric fans would in fact work 99.9% of the time and even then the second fan might only be for insurance.

For me the reason I have no interest in an electric fan (besides that I want to retain the full capacity) is it's adding complexity where I don't feel I need to add it. The small increase in MPG or HP daily isn't enough to justify all the extra wiring and failure points. About the only issue with the stock fan that is critical is breaking blades. The worst case is the coupler stops working and the fan stops turning. The fix for that is a trail-side 'rebuild' filling it with mud or RTV. Then you will never overheat, so it's a fail safe.

 

This is a valid reason, the Flex-a-Lite dual e-fans that were on my 04 (previous owner had them installed) not only did a poor job keeping the engine cool when offroading, but the final straw happened one day when I was on my way to work. Noticed white smoke coming out from my wheel wells when at a stop light, I pulled over and popped the hood and saw a small fire where the wiring harness to the e-fans was. Not sure what happened or why but it had caught fire, I put it out and drove straight to my mechanic and had an OEM fan system re-installed. No issues since. I was very lucky too that the failure didn't happen when I was out wheeling somewhere remote, that would've been bad.

Not saying the is a probable outcome for e-fan setups, for all I know the PO did the install himself and botched it, or someone else did. But like you said, it does add complexity where it isn't necessary. The OEM fan setup works beautifully for me now, I don't overheat at all and I can finally use my A/C while in 4wd (couldn't before or it would almost be guaranteed to overheat).

 

Reasons I went e-fans on my previous vehicle:

1. The clutch driven fan sounds dumb
2. I can run an e-fan if I want to, this is 'murica

Who needs any other reasons? Y'all are having some deep discussions regarding airflow apparently without anyone knowing what the stock airflow actually is, which seems silly.

 

This is a great summation Dave! I will say though, that for vehicles that occasionally cross deeper water, being able to cut out the fan is a very nice feature. It is also nice to cut the fan when trying to warm up a VERY cold engine. I have had to block my radiator due to cold. We need a mod for an OEM fan cut out. The issues of reliability always come in with electric fans. On the vehicles where I experimented with them, I never left home without the OEM fan after that first overheat in the Sierra Nevada. In the end, I always went back to an OEM fan.

 

You should look into the 90s V6 Ford Taurus fan. I've heard great things about them and you can prob score one for $20 at a junk yard or $100 new.

 

Yes they are disputable because an alternator doesn't rob more power from the engine as the electrical load goes up. All he has done has been to show calculations out that show hp loss and gains without any "REAL WORLD" proof or data on a dyno. I wish I had all the dyno sheets and time to show this but I have spent hrs. upon hrs on dynos doing testing and working on squeaking every last hp out of vehicles or drivability. I am not disputing his thoughts that the engine driven fan is better at it's job I can definitely stand behind that and not disputing the alt. output curve I have made many of those in my day and tested a lot of this stuff in the field with equipment. The alt. is essentially an electric motor in and of itself. as it produces more power it in turn is producing the HP to make that output base off the engine turning it the alternator is a semi-constant parasitic drain, similarly to other idler pulleys etc.

I can get with most of this. I don't get why you think it adds more complexity, the only sector in the automotive market to not run electric fans in the truck side, and even then there are some that run a small pusher in front of the condenser to help move more air. The whole complexity and fear of more failure points was arguments guys were having back in the day when electric fans first hit the market. Is it more complex and are there some more failure points sure but not that many. If you don't want to run them because why mess with what toyota did thats cool. I also still don't agree nor will ever that you loose HP as the eletrical load goes up. The alt. output stays constant at a given RPM regardless of load and doesn't cause more robbery of engine HP. I do say the alt does rob some HP from the engine hence why pure drag race cars do not run them. The viscous may in best case scenario semi work to the way it's intended but in my experience once it's gotten to it's temp locked and never really slips any from there, maybe a tiny bit here and there but not anything significant, it's old and antiquated. Thankfully toyota does not have the plastic fan issues ford or chevy do or you would be taking a spare with you on the trail, seen many of those come apart, just because weren't hit by anything.

 

I have run these on a bunch of different vehicles with the flex-a-lite temp sensors and their controllers. It has to be the first gen taurus though. If you get the whole shroud and everything that is the way to go. It's a dual fan unit. I am not sure if they will fit our radiators that well though may be too small. I was wondering if anyone knew about this one.

 

I'm having trouble following your line of thought, but we need to get a couple of things straight. The load that an alternator presents to the engine is directly proportional to the electrical load. This is fundamental to electric machines, it's dictated by Lenz Law. This is measurable, repeatable and indisputable. It doesn't violate physics, specifically the 1st law of thermodynamics and the conservation of energy.

The efficiency of an alternator must always be less than 100% and in real devices will have a curve similar to the one I showed. Very good automobile alternators have 60% peak efficiency and on average it's in the 40% range and may in fact be much worse at a given RPM, load and temperature.

Going the other way, a motor will have a similar efficiency vs. performance characteristic. These are usually better than alternators, but an example permanent magnet DC motor will look like this one.



If you need 3,300 cfm it takes some amount of power to do that. That was the work-flow formula, this is a function of the friction due to blade size, pitch, air density. Say that takes 1 HP, you need to put 1.2 HP into the motor to achieve it to overcome for the losses in the motor. That means the alternator, neglecting cable losses, needs to generate that 1.2 HP. Since it's at most 60% efficient that means you need the engine to produce 2 HP input to the alternator. This further neglects mechanical losses in the belt, bearings, etc. But the system efficiency is 50% in this example, which is a very realistic outcome.

This is physics, it's not conjecture, it's not speculation. It's how the world works. Whatever you do on the dyno won't disagree with this. There's ways it may appear not to be the case, for example as I mentioned in a post some time ago, the battery is storing energy you generated earlier so an instantaneous power measurement might not be fully loading the alternator and thus not loading the engine. But over time it will. If the alternator didn't produce the energy to turn the fan at that moment it will have to produce it later to charge the battery. The average power will always balance.

A simple example of this is a generator, a Honda EU1000 for example, which is an engine directly connected to an alternator. The engine in that is a Honda GXH50, which develops 2.1 HP at the crankshaft. That means 1,566.6 mechanical watts are needed to generate 1,000 electrical watts. The inverter in that unit is probably about 88% efficient, meaning the alternator actually generates about 1,136.4 watts before conversion to 120VAC. So their apparent mechanical-to-DC conversion efficiency is 72.5%, which is indicative of alternators in general.

 

I love fans. I have many