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Is the stock electric fan enough to cool on its own?
- Thread starter ZmOz
- Start date
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Drag strip cars in the '70's ditched the viscous fan for electrics - even put in an electric water pump to cool the engine after shut down, in some classes. Plus a little more HP to the ground, less mass to accelerate, etc.
Some designs require electrics - say, the four cylinder transverse Caravan, for one. No easy way to run the belt another 90* on edge.
Check out a famous "dyno" mite website for specifics.
Some designs require electrics - say, the four cylinder transverse Caravan, for one. No easy way to run the belt another 90* on edge.
Check out a famous "dyno" mite website for specifics.
Even if an extra factory aux fan would pull enough air through the radiator you won't have enough clearence. Open your hood and measure how deep the factory electric is and the measure the distance between the radiator and the original fan pully. You'll need a thinner profile fan.
mattb
NAXJA Forum User
- Location
- Las Vegas, NV
I recently went through the whole eletric fan vs. mechanical fan issue. At the same time I also replaced my radiator, water pump, fan clutch and thermostat.
Before I get into my results, to address the amperage question, I don't have an exact figure but its probably around 12-15 amps. When running both the aux fan and a secondary electric fan (9amps) I would blow a 20amp fuse. The aux fan alone would not blow the 20amp fuse.
As background, I did these tests in 100 degree temps in the Desert during slow 10+ mile offroad hill climbs.
What I found was that the new style OEM aux fan performs just about as well as the Mechanical at extremely slow speeds. I also found that this OEM fan performs very well compared to other electric fans, and better than the FLEX-A-LITE that a lot of people use. In addition I discovered that 1 fan alone of either type isn't really enough to cool the vehicle in extreme temparture slow driving especially if you want any AC at all.
What I ended up running is the stock Mechanical fan and the AUX OEM fan set to start at 200 degrees not the standard 220.
The people who really hate the electric fans, I found are those who expected it to solve an over heating problem and were disapointed in the lack luster results. It really doesn't do any better than the mechanical and can add complications.
Matt
Before I get into my results, to address the amperage question, I don't have an exact figure but its probably around 12-15 amps. When running both the aux fan and a secondary electric fan (9amps) I would blow a 20amp fuse. The aux fan alone would not blow the 20amp fuse.
As background, I did these tests in 100 degree temps in the Desert during slow 10+ mile offroad hill climbs.
What I found was that the new style OEM aux fan performs just about as well as the Mechanical at extremely slow speeds. I also found that this OEM fan performs very well compared to other electric fans, and better than the FLEX-A-LITE that a lot of people use. In addition I discovered that 1 fan alone of either type isn't really enough to cool the vehicle in extreme temparture slow driving especially if you want any AC at all.
What I ended up running is the stock Mechanical fan and the AUX OEM fan set to start at 200 degrees not the standard 220.
The people who really hate the electric fans, I found are those who expected it to solve an over heating problem and were disapointed in the lack luster results. It really doesn't do any better than the mechanical and can add complications.
Matt
mattb
NAXJA Forum User
- Location
- Las Vegas, NV
The new fan style came out in 1993.
Matt
Matt
mattb
NAXJA Forum User
- Location
- Las Vegas, NV
On one of my first runs with new Flex-a-Lite fan it flexed and jammed up in the radiator casing, breaking two blades. Since the performance wasn't really any better I went back to the mechanical since it's been reliable in the past.
The breakage was part my fault and part the fan being flimsy and too big. Despite people saying the flex-a-lite 110 is the perfect size for the XJ its really too tall by about 1/2"-3/4". For the electric fan to have a chance of being as good as the mechanical it has to sit really tight against the radiator (creating a good seal and moving the maximum amount of air through the radiator.) This is a bit difficult with the aftermarket 3 core radiator I installed (I believe the stock would have the same issues.)
The one hold over from the Flex-a-lite install is the control relay. This is a really handy controler I now use for the aux. fan. It has an adjustable thermostat, and an input for the AC compressor and an over ride switch to force the fan both on and off.
Enjoy,
Matt
The breakage was part my fault and part the fan being flimsy and too big. Despite people saying the flex-a-lite 110 is the perfect size for the XJ its really too tall by about 1/2"-3/4". For the electric fan to have a chance of being as good as the mechanical it has to sit really tight against the radiator (creating a good seal and moving the maximum amount of air through the radiator.) This is a bit difficult with the aftermarket 3 core radiator I installed (I believe the stock would have the same issues.)
The one hold over from the Flex-a-lite install is the control relay. This is a really handy controler I now use for the aux. fan. It has an adjustable thermostat, and an input for the AC compressor and an over ride switch to force the fan both on and off.
Enjoy,
Matt
Thanks again, Matt. I have had similar problems when I forget I'm the engineer on the fabrication and something got me. So now I ask lots of questions from experienced folks.
The radiator retrofit changes all the dimensions and obviously it becomes more complicated with an aftermarket fan. Stuff you need to know if the mod looks attractive.
Proves it ain't always as easy as it looks. And yes, the factory gurus have their days too, look at the military Hummer fans - plastic - they will shear blades when you hit the water fording, and then overheat 5 miles down the road. So far the best solution is Don't Do That, Private!
The radiator retrofit changes all the dimensions and obviously it becomes more complicated with an aftermarket fan. Stuff you need to know if the mod looks attractive.
Proves it ain't always as easy as it looks. And yes, the factory gurus have their days too, look at the military Hummer fans - plastic - they will shear blades when you hit the water fording, and then overheat 5 miles down the road. So far the best solution is Don't Do That, Private!
I did it and it was Ok.
I shorted out my flex a lite 110 fan during a trip and had to go 200 miles in 75* weather with just the factory electric aux fan running. I had it on a manual switch, so it didn't wait until the 218* ECU limit kicked it on. It ran about 210 all the way home (highway driving mostly). The flex a lite 110 pulls about 1.5X the amount of air as the factory electric fan. Both together work well. I wouldn't expect the little factory fan to cool all by itself in all seasons, regardless of where you drive it.
I shorted out my flex a lite 110 fan during a trip and had to go 200 miles in 75* weather with just the factory electric aux fan running. I had it on a manual switch, so it didn't wait until the 218* ECU limit kicked it on. It ran about 210 all the way home (highway driving mostly). The flex a lite 110 pulls about 1.5X the amount of air as the factory electric fan. Both together work well. I wouldn't expect the little factory fan to cool all by itself in all seasons, regardless of where you drive it.
rockwerks
NAXJA Forum User
- Location
- Chito Beach Resort, WA
even at best it only works in cool climates, if you live in the southwest it won't work
here is my experience with this:electric fan myth
fix your cool engine problem by putting in a thermostat no lower than 195*
MaXJohnson
NAXJA Forum User
- Location
- The Kansas Rockies
160°!
I'd be wondering if the temp gage is worth a sh!t. XJ's don't (and shouldn't) run that cool.
The only valid reason I remember for running all electrics is to have the ability to shut them off for water crossing. Sure, the drag race guys do it, but are you planning on shutting down for a cool down session after every 1/4 mile?
You don't spin a fan with free energy. If it takes X horsepower to run it off the crank shaft, it takes X horsepower to run an electric motor. There's an inherent inefficiency converting the rotating motion of the crankshaft to electricity and then back to rotating motion at the fan blade. A good percentage of it turns to heat without doing any useful work. How much gas is that saving?
I'd be wondering if the temp gage is worth a sh!t. XJ's don't (and shouldn't) run that cool.
The only valid reason I remember for running all electrics is to have the ability to shut them off for water crossing. Sure, the drag race guys do it, but are you planning on shutting down for a cool down session after every 1/4 mile?
You don't spin a fan with free energy. If it takes X horsepower to run it off the crank shaft, it takes X horsepower to run an electric motor. There's an inherent inefficiency converting the rotating motion of the crankshaft to electricity and then back to rotating motion at the fan blade. A good percentage of it turns to heat without doing any useful work. How much gas is that saving?
MaXJohnson said:
First, I know my gauge is working because if it idles for a long time or it's REALLY hot out and I'm in heavy traffic it will go up to 200-ish...but rarely. My dad, who drove it since it was new, says it's allways ran cool like that. I did buy a new thermostat and I'll probably put it in sometime soon.
As for the electric fan idea, it takes a hell of alot more energy to spin that big old metal fan blade and viscous clutch than it does to spin an electric fan. Most electric fans use about 15 amps, at 12 volts that's only about 1/4 of one HP. I can gaurantee you that if you hooked up the mechanical fan to a 1/4" motor it wouldn't spin nearly as fast as it does in the XJ. Not only that, but the mechanical fan is ALLWAYS putting a load on the engine. With an electric fan it will turn off at high speed, putting absolutely no load on the engine.
I'm not doing this for speed, although that's a nice side effect, I'm doing it to save ~2mpg. And don't give me that shit about it only working in cool climates...read Dino's page about it. http://www.angelfire.com/my/fan/electric.html
He lives in Saudi Arabia, where it gets HOT, and says it works great with the AC blowing on a 120 degree day.
Rev Den
NAXJA Forum User
- Location
- Plainfield, IL
3 pages of this here, who knows how many on JU,.....why did you ask? Sounds to me like you already had your mind made up. You have heard from very knowledgeable folks here who have told you...for the most part...no. OK, fine, do it...write it up and let us know, prove us wrong. The answer to your original question is in Dino's page that you quote,
"Finding a fan that fits within the confines of the engine bay with the 4.0 liter engine isn't easy. There is very little space. An electric fan assembly from another XJ is not slim enough"
Rev
"Finding a fan that fits within the confines of the engine bay with the 4.0 liter engine isn't easy. There is very little space. An electric fan assembly from another XJ is not slim enough"
Rev
MaXJohnson
NAXJA Forum User
- Location
- The Kansas Rockies
ZmOz said:
That's hardly proof that your temp gauge is working correctly. It could be off by 40° and behave exactly as you described. As for the big heavy engine driven fan, most of the energy we're talking about here is to move the air, not to rotate the mass of the blades. Both types of fans have to move the same amout of air to provide the same degree of cooling.
I'm with Rev Den. You seem to be predisposed to convert to all electric, so do it. Let us know how it goes, but try to be a little more scientific in your methods. And let us know if our opinions turn out to "shit".
MaXJohnson said:I'm with Rev Den. You seem to be predisposed to convert to all electric, so do it. Let us know how it goes, but try to be a little more scientific in your methods. And let us know if our opinions turn out to "shit".
Yes, I decided a long time ago I was going to do this. What I am, and was, asking here is if the stock aux fan would be big enough and if not how many CFM do I need. It is a proven fact that an electric fan moving the same amount of air will use WAAAAAAAAAAY less power, as well as making the water pump bearings and the belt last longer...
vintagespeed
NAXJA Forum User
- Location
- Upland, CA
Yes, I too am going to do this mod. Every 90* import motor uses an electric fan setup, even the V6s. Why? Because they can't mount the radiator on the passenger side fenderwell..... How often do import motors break down because of overheating...........Bueller? Bueller?
Anyway, I like the idea of running the fans at a constant speed as opposed to the mechanical fan spinning at engine speed. When you pull off the freeway and your motor spins down to idle from high-rpm (efficient) speeds, does your temp guage go up? Sure it does. You're going from high-flow to no-flow. I think that with a constant speed fan the temp change will be less drastic.
My .02.
Anyway, I like the idea of running the fans at a constant speed as opposed to the mechanical fan spinning at engine speed. When you pull off the freeway and your motor spins down to idle from high-rpm (efficient) speeds, does your temp guage go up? Sure it does. You're going from high-flow to no-flow. I think that with a constant speed fan the temp change will be less drastic.
My .02.
rockwerks
NAXJA Forum User
- Location
- Chito Beach Resort, WA
Yes, I decided a long time ago I was going to do this. What I am, and was, asking her
THERE IS NOT A SINGLE DUAL OR TRIPLE FAN UNIT OUT THER THAT WILL MOVE THE REQUIRED AMOUNT OF AIR TO WORK BETTER OR EQUAL TO THE STOCK SETUP
If you wish to waste your time and money trying something that many of us have already wasted ours on and dont wish to listen to experience then go ahead and do it but don't waste our time asking the questions if you aint gonna listen
THERE IS NOT A SINGLE DUAL OR TRIPLE FAN UNIT OUT THER THAT WILL MOVE THE REQUIRED AMOUNT OF AIR TO WORK BETTER OR EQUAL TO THE STOCK SETUP
If you wish to waste your time and money trying something that many of us have already wasted ours on and dont wish to listen to experience then go ahead and do it but don't waste our time asking the questions if you aint gonna listen
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