Electric fan vs. Belt-driven fan

[evoracer306]

I just had a thought and was wondering if any of you could help shed some light on it for me. I am using a friend's '96 Dakota 4x4 with the 5.2L(318ci)V-8. I am getting around 13MPG right now. The thought I had deals with the belt driven radiator fan. I had a friend that replaced his belt-driven fan in order to reduce parasitic loss and gain some power. I would think that this decrease in parasitic loss would result in a little more fuel efficiency. Any thoughts?

Todd

[Snax]

It would definately provide a slight increase in efficiency, but it's not likely to be noticeable. You'll likely save more fuel by simply shifting it into neutral at every stop.

[Mentalic]

If the existing fan clutch is working properly switching to electric will not make a noticeable difference. I've tried it and went back to the fan clutch for its simplicity and ability to cool when towing.
You would get better results just keeping your tires inflated.

[froggy81500]

clutch or not, the mechanically driven fan still spins, albiet at slower speeds when not needed. An electric fan will only run when it is needed. Warm up times with an electric vs mechanical fan can be quicker in the winter time because the fan is not running when it is not needed.

[kamesama980]

the problem with a mechanical fan, clutch or not, is that every time you change RPM it's more rotating inertia to overcome. this is, of course, all going to be relevant to what kind of driving you do (very little if any difference on the highway), engine, and vehicle. a 5.7l v8 probly won't notice it much at all but a RWD 4 banger probably will very much so. I wouldn't count on it being a night/day difference but it may show itself over time in a few % gain in FE

[brucepick]

There are posts above indicating that other things will give you more benefit than you'd get from the e-fan. Probably true.

However you should do those other things anyway. You don't have to make a choice between tire pressure and an e-fan. Same for neutral idling instead of in Drive.

Generally you'll get FE improvement by making a bunch of changes. Some are easier than others. It's the combined effect that will add up to something.

The e-fan was the first FE mod I did on my car. I have to admit I haven't been able to document that it's helped with fuel economy. The car is pre-'86 so no ScanGauge and also, switching fans is a bit of a pain so doing a comparison test would be a challenge. However, all told, the car is doing well as far as FE goes.

In my case I wouldn't change it back. The car is a bit underpowered by most standards so anything I can do to "unload" the engine is helpful. If you do put one in, I highly recommend an LED on the dash to let you know when it's running. I can't hear mine come on even when idling at a stop so the LED is the only thing letting me know it's working as expected. I definitely want to know the fan's working!

[dkjones96]

I've gone from a mechanical fan to an electric fan before and if your fan clutch is in good condition I think you'll like the difference in mileage. I personally will never swap out a mechanical fan again.

I realize that on the freeway most cars don't need a fan pulling air and a perfect mechanical fan or a true 'clutch' fan wouldn't be. But, it does, always. Only a mechanical fan with a badly worn clutch will you not see much of a gain, if any, by swapping out. A good mechanical fan clutch will get fairly stiff at idle. It'll take a good 10-20 seconds to loosen up after you take off from the stop. On the freeway the radiator will warm the clutch and it will be pulling air, more air than the radiator will flow on it's own. In my old car that got converted to electric fan, anything above 90 for extended periods even with the electric fan on it'd start to heat up. This is in a car that would ran regularly 110-120mph for 2-3 hours straight no problem before the conversion.

A typical stock mechanical fan flows a maximum 10,000-11,000 cfm and typical electric fans flow a max of about 3,000-3,500cfm. This is important because the less air you move the less energy, however, electric fans are nowhere near as efficient as mechanical fans at moving the same amount of air since you have to convert mechanical to electrical then back to mechanical and that has losses.

There are some plusses but also negatives. It's up to you as to what you want to do. I'm sure if you are going for FE it'd be best to do away with it. If the truck does any actual work I wouldn't recommend it.

[VetteOwner]

on my s-10 (has a 4 banger) i noticed a 1-2 MPG increase when i went from clutch fan to electric fan, heater got warmer quicker, fans never on at highway speeds, maintains cooling even on the hottest days and while towing.

id love to do it to my chevette (non cluch fan, bolted straight to the pulley) because obviously with that small of an engine i need all the oomph i can get (frees up some torque) an dwhen torque is freed up and not wasted in a fan at cruising speeds then thats more torque available to go to the wheels thus less gas needed to do the same ammount of work

[froggy81500]

I had two chevettes, a 1980 Scooter that had an auto that slipped between 1st and 2nd upshift, and then later a 1981 4 dr with a 4 speed. Those cars could take a beating.

[bobc455]

The fan in my Saturn has not worked for the last 8 months. You really don't need it, as long as the car is moving.

BTW a mechanical fan doesn't draw as power as people might think, because if the car is moving forward at 35MPH and the fan is trying to pull air at 35 MPH it works out to nearly zero.

On the other hand, it's nice to get rid of some weight on the water pump bearing, in my experience the water pump's life will about double.

-BC

[kamesama980]

at that exact point where the fan rpm and airflow matches the vehicle speed...yes they're fine. but that depends on engine rpm, gear, speed, etc. the other 95% of the time, they are still dragging. the arguement is the additional inertia to accelerate/decelerate the fan, not the cruising drag.

as with what DKjones said, at very high speed and engine rpm, they do still do something. but not many of you guys are gonna be more than halfway to that speed :-p

[dkjones96]

as with what DKjones said, at very high speed and engine rpm, they do still do something. but not many of you guys are gonna be more than halfway to that speed :-p

haha, I miss that car. One of the few cars I've ridden in that felt so confident and sure at high speeds, I'd even set the cruise. I loved that 2.8L 12V DOHC L6. None of that 4 valve per cylinder mess.

The engine turned about 4200-4500 at those speeds but it'd still get in the 22-25mpg range after a 350 mile trip with an average speed of 105-110. Not that I'm surprised about that, it's right there at the torque peak.

[VetteOwner]

I had two chevettes, a 1980 Scooter that had an auto that slipped between 1st and 2nd upshift, and then later a 1981 4 dr with a 4 speed. Those cars could take a beating.


its true, i had to replace a burnt valve and there was virtually no carbon build up in it! mine starts in all weather conditions, bit annoying in summer with vynal seats tho (burns like mad):p

betcha want one of em back (prolyl the manual, heard the auto chevettes had no power to get up hills lol)

[8307c4]

I've done this on a 1988 Ford Thunderbird 5.0, removed the clutch driven fan and installed an electric thermostat-driven one. Although the initial installation is relatively simple the entire process is not a one-afternoon thing.

The thermostat needs to be re-adjusted periodically until such time the fan acts right, and comes on when it should and shuts off reasonably as well. I would say this process takes several months of driving and watching and monitoring temperatures, then adjusting if needed etc.

A simple fan used to cost 80 dollars, you really need two for a V-8 but all I could afford at the time was one, it does fine like this but you really could use two.

Then by the time it was all said and done, I neither noticed any increase in mpg nor power, so in all honesty I could've just saved myself a lot of time and money.

You can do it out of principle, but it's not something I'll ever do again...

[Dust]

I saw some testing of Surf mechanical fans, and increasing the amount of fluid, or turning something or other made the fan work better, or worse. I think the worse they showed was a 20% loss in mileage. the more it works, the more fuel it takes.

I think that if the engine can take a bigger alternator (Foxbody to next style mustang style swap), and you can get a good fan (MKVIII, or Ford Escort, etc.), then you should probably do it. It will be one less drag on the engine, and I think that 10-20 hp has been picked up in similar sized V-8s.

[brucepick]

I also used a lot of trial and error to come up with a fan switching setup that I really like. However if I were to buy another Volvo 240 I would certainly swap in the fan project from this one. As I wrote in my other post, I can't flat out document that it helps FE but I'm pretty sure it does.

[itjstagame]

I've been wanting to do this for some time. I had an extra fan from a junked Caprice and bought the $17 thermostat kit from Advance. I've been trying to find time to do it for 6 months.

Well last night I finally did it. I probably spent 4 hours on it and it's not 'really' done yet (or properly that is). Anyway I ghetto rigged it as much as possible, I used one efan from a 2 fan setup on a 9c1 impala and soldered the thermostat and relay directly (so if the relay goes I have to resolder). My truck already has a smaller radiator than normal, some odd ball thing that the previous owner threw in when his stocker started leaking. So I already noticed some cooling issues in summer and will probably swap back to the mechanical fan for summer.

But for winter I figured the efan HAD to help. My truck is already warming up pretty quick because of the HAI, but I wanted it to heat up quicker since my commute is only 15 mins or so. That clutch fan is ALWAYS spinning. I realize it's only supposedly doing work when it needs to, etc, but it's always spinning quite fast and due to the swapped radiator I never had a fan gaurd installed (that is the previous owner didn't reinstall it and I don't have it).

So I had a couple reasons to do this. The mechanical fan came off quite easy (though I did get snowed on and was cold for 3 hours afterward, this was midnight btw), it weighs a good 20-30 lbs. The serpentine assembly looks a lot cleaner without it and the electric fan installed quite easily and doesn't seem to rub at all against the radiator (a concern of mine).

It's fully off at any speed above 40MPH because it's friggin' 15F outside. Only at a stop light will it come on and I've got it adjusted pretty well right now. I don't see why it'd take a few months, I mean I probably stopped 4 times or so to check and adjust and now it's pretty good. I gained a good 20F now on local roads. The mechfan always kept temps at 170F (on my gauge anyway, I know I have a 195F thermostat, so something is off somewhere) and now it comes on just before 210F and shuts off at 190F and stays pretty much at 190-195F the whole time. This was the other reason I wanted the efan, to control my temps a bit more.

It doesn't seem like it draws that much power, I think the specs for the 9c1 said it was 150watt, but I can barely notice the draw on the engine (though it is there if you listen for it, a bit less than using the headlights). Also the truck is MUCH quieter. I guess that howl that I thought was my intake was just the mechfan! It's quieter and seems smoother with that mass removed.

I have noticed more HP, but no extra torque. That is I accelerate at the same speed but 2 hills on my commute where I usually start at 60MPH and end at 50MPH I was going 55MPH at the end of them today (without downshifting). And a hill I would normally have to downshift at and I figured I would have to slow down and I went up to maintain gear, I was AMAZED how little throttle was required to go 65MPH up it.

Only time will tell if it helps MPG, but so far I warm up a bit quicker (not too much slow, I think I need a bigger grill block) and definately notice a few more horses and the install is just cleaner.

Of course, I should fix it a bit. Right now it's wired directly to the batter because it was midnight and I wanted to see it work, but I need to pull a good keyed power source, loop it through a 12v LED and send it to the thermostat, so it stops running when off. I also need to wire in a direct switch.

Last night I just couldn't find a good keyed power source or a place to push through the firewall easily.

[VetteOwner]

yea V8's you arent going to see much of an increase because the engine already makes a whole lotta power that you dont need all the time. but 4 cyl engines dont have too much power to spare so they see the biggest gains from Efans.
i did notice that my truck was MUCH quieter when idling. Before you would rev it and all you would hear was a second of engine rev then the fan drowns out everything...

[itjstagame]

Well I wanted to add that upon more driving I feel that the steering is a bit lighter, like less weight on the wheel when changing directions.

Also I finished one tank, not sure it means anything, only the average will tell.