Replaced viscous fan with a 16" electric!

I have just had great success replacing the stock mechanical fan with a 16" electrical one. I now have quieter running, faster pick up and better fuel mileage to boot. Even removed the fan bearing pulley for even less resistance!



Check it out on my site.

You're such a rebel.....everyone knows that couldn't possibly work.

Only joking, hope it works well for you.

Does the fan spin backwards on the other side of the equator?

Dan

Nice job Marcus! Chalk another one up in your growing column of winning mods.

Great write-up. I've read of several people who've done this swap and then had cooling problems, but the write-up points up several possible causes and does various things to overcome those problems. I know it's not yet full summer there yet, but have you been able to test it in the heat?

One question about the HP gain. This might be a dumb question - the dumb part is I don't know how the alternator works when it senses the batteries have a full charge, does it disengage or does it keep generating electricity but just discharge it? Assuming it disengages somehow, it seems like you really won't save HP because what you gain from not running the fan, you would lose from having to run the alternator longer.

interesting difference in the RHD/LHD stuff -- should be worth a good look-see though -- If I'd'a thought about cutting the fan bearing as you've done I'd prolly still be running my electric...

(hmmm, thanks as usual!)

Well I have run it in traffic with aircon on and it was 100*F outside. How much hotter do you want it?

As for the alternator, it does not dis-engage at any time. It is not like the aircon compressor which does and is the only thing that I know that does it.
I have added some more possible fans to use for you guys in the States as well. Even a GOLD PLATED one rated at 2700 CFM though for all it's bling!

Hows this one for something different!



Rated at 2950 CFM!



Also in a 14" at the same 2950 CFM

Might be able to mount them directly to the back of the stock shroud. The 14" would need the extra inch all the way around filled in though.

It's true the alternator uses power to run the fan...but the fan does not run all the time such as when highway cruising...I installed a similar fan in my truck..it made a noticable difference in power and is much quieter than the flex fan that was in it...no probs with running the A/C either.

Well, Marcus, if anybody can make it work I expect you can. I've just heard too many stories of the electrics failing to cool at peak loads. And, yeah, 100 degrees in traffic with the a/c on is a pretty good test - the only better test will be when you pull your trailer crawling up a steep mountain trail, with the a/c on and 100 degrees outside, which I'm sure you'll do before long. Let us know how that goes. Meanwhile, congratulations and thanks for figuring out how to make the idea work.

I'm still inclined to think overall fuel consumption is going to be higher, due to the efficiencies lost converting to electric and back to mechanical power. But the difference can't be much and that's a small price to pay for the benefits you gain.

Anybody know the CFM ratings for the stock belt fan at various RPMs?

92xjsp said:

I'm still inclined to think overall fuel consumption is going to be higher, due to the efficiencies lost converting to electric and back to mechanical power. But the difference can't be much and that's a small price to pay for the benefits you gain.

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Are you kidding? The alternator does not have a clutch, and does not kick in extra juice to the elecrical system at times of high draw. Its a function or RPM soley.

i got an electric fan installed also.

92xjsp said:

Well, Marcus, if anybody can make it work I expect you can. I've just heard too many stories of the electrics failing to cool at peak loads. And, yeah, 100 degrees in traffic with the a/c on is a pretty good test - the only better test will be when you pull your trailer crawling up a steep mountain trail, with the a/c on and 100 degrees outside, which I'm sure you'll do before long. Let us know how that goes. Meanwhile, congratulations and thanks for figuring out how to make the idea work.

I'm still inclined to think overall fuel consumption is going to be higher, due to the efficiencies lost converting to electric and back to mechanical power. But the difference can't be much and that's a small price to pay for the benefits you gain.

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I removed my viscous clutch fan three years ago and replaced it with a 12" electric fan that sits alongside the factory auxiliary electric fan. I also noticed a slight improvement in performance and gained over 1.0mpg in city driving. My set-up has survived three 115*F summers very well, and sat in crawling traffic with the A/C running full blast with the temp. gauge just barely getting above halfway.
As long as you select a decent size fan that pulls enough air, you won't have any overheating problems and you'll get the performance/gas mileage benefits as well. It's all good.
The stock clutch fan is next to useless. As far as I'm concerned, it's little more than a 5lb weight applying drag to your engine.

Dr. Dyno said:

I removed my viscous clutch fan three years ago and replaced it with a 12" electric fan that sits alongside the factory auxiliary electric fan. I also noticed a slight improvement in performance and gained over 1.0mpg in city driving. My set-up has survived three 115*F summers very well, and sat in crawling traffic with the A/C running full blast with the temp. gauge just barely getting above halfway.
As long as you select a decent size fan that pulls enough air, you won't have any overheating problems and you'll get the performance/gas mileage benefits as well. It's all good.
The stock clutch fan is next to useless. As far as I'm concerned, it's little more than a 5lb weight applying drag to your engine.

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Lucas said:

Are you kidding? The alternator does not have a clutch, and does not kick in extra juice to the elecrical system at times of high draw. Its a function or RPM soley.

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Well, I’m no expert, but my rationale is based on the idea that there ain’t no such thing as a free lunch. If you have two identical fans, one electric and one belt driven, it *has* to take a little more fuel to run the electric one, because of the power lost to the inefficiency of converting mechanical motion to electricity and back to mechanical motion again.

Now, to the degree that the fans aren’t identical, you have room for improvement. If the belt-driven fan produces too much air flow, more than you need, then maybe you can gain HP and fuel economy by converting to a less powerful one that produces exactly what you need. Or, if the stock clutch fan is a particularly bad design, you can gain by getting a better designed one. I’m assuming that the stock fan is a decent design and that most XJs need all the cooling it can produce (otherwise why would we need the aux fan), so that’s why I said it’s likely to cost you gas mileage. I realize those assumptions could be wrong – Dyno, I guess you’re saying the stock fan is a bad design? Can you tell me more about what makes it a bad design? Is it possible to get specs on how much energy it uses to produce how much airflow versus electrics?

Like I said, I don’t pretend to be an expert on this stuff, I’m just trying to learn. I’d be happy to be proved wrong because that means I’ll learn something new. Marcus’ post got me thinking about this, and I had to ask over on the OEM side just exactly how an alternator worked. I figured it didn’t produce it’s max output all the time because I didn’t see any way it could get rid of the excess electricity. They told me over there that, although it does run all the time, the load it pulls (resistance on the belt) is variable based on the current demands put on it. That means that if you’re using an electric fan, you save the fan’s load on the belt but in place of it you have a heavier load from the alternator. Since I know there is a small amount of power lost in the process of converting mechanical energy to electric and back again, it makes me think there is a small overall power loss, although there could well be a peak power gain that results from using battery power temporarily.

BTW, I’m not saying electrical fans are bad, there are a lot of arguments in favor that have nothing to do with the power equation.

its true that there is no free lunch and takes electricity to run the electric fan. i had mine on for about six month now.
but my electric fan only runs at idle and not even all the time at idle. it cools enough at idle to shut off.

so as long as i am moving in city or on freeway the fan is off. so imagine a 5 hour freeway trip were the fan never comes on. thats got to add up for some power and free gas. jack

Gojeep said:

Well I have run it in traffic with aircon on and it was 100*F outside. How much hotter do you want it?

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When I'm coming back from work in traffic during summer.... it gets to 115F + and I think your traffic does not even compare to our traffic but it might be interesting to see someone test it out over here....

No need to test the electric fan over there Kejtar. I've already tested my electric fan setup in three 115*F summers and it passed the test with flying colours. I couldn't get the engine to overheat even when I was wheeling in the desert in mid-summer.
The electric fans stay on when I'm using the A/C and they cycle on when the coolant reaches 220*F when I'm not using the A/C. For about six months of the year, the fans are off at least 90% of the time saving energy and fuel.
The stock clutch fan cannot keep the engine cool on its own. At idle, the coolant temp. rises steadily to 220*F and then the electric fan kicks in to bring it down again. If you disable the electric fan, the coolant gauge will eventually reach the red zone. That tells you just one thing about the clutch fan; it's a completely useless 5lb piece of junk!

Jack SF hit the question-nail squarely on the head.

MudDawg said:

Jack SF hit the question-nail squarely on the head.

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Yep, and Dr Dyno too. Ya'll definitely have me rethinking. But still, the clutch fan isn't always on, either, it only comes on when the engine reaches a certain temp. Is there a difference between when the trigger temp between clutch and electric fan? That would be the only way you could leave one off for months at a time while the other one is running. And that has nothing to do with fan performance - both have equal performance when they're *not* running

Another, more general argument against what ya'll are saying is this - there are TREMENDOUS financial incentives for the car companies to report even slighty better fuel economy numbers. If they're running a crappy-design clutch fan and they could gain 1.0 MPG by changing to a well-designed electric, that would mean mega-millions to them. Why didn't they make the switch?

i looked for a fuel gain but i did not get it. or at least it was so small i did not notice it. most of my driving is city.

a lot of comapanies run electric. most of the japanese cars are electric. and they are known for fuel economy. i ithink that its simpler to run a fan clutch thats why they do it. less seized up engines. if you want simplicity than stay with a fan clutch, but i did not build up xj for simplicity.
if electric is good enough for Lamborghini with 585 hp than its good enough for me. jack

I agree with the no free lucn idea, but its not like the alternator doles out precise amounts of electricity to run whats demaded at one particular time. The alternator produces x amount of electricity for x00 rpms. Whats not used by your fan/stereo/ignition is used for the charging system. The alternator, at least not on a jeep, has no feedback system to tell it how much juice to put out other than engine speed.