Hi Folks,

A few months ago I won a new Flex-A-Lite II 475 electric fan for my Jeep TJ.

Here are my notes and the results of some testing I did on this fan and the original equipment mechanical fan/clutch on my Jeep.

My TJ is a 97, 4.0L with 5sp and A/C. There is a winch in front of the grill. I also have a 3-core radiator, a 195 degree F thermostat and to the best of my knowledge a perfectly functioning fan/clutch.

All tests were done in Kentucky at humidity levels above 80%.


First Impression:

The fan is well built.


Second Impression:

This Sucks!

Apparently the same fan kit is sold for both TJ’s and YJ’s.

In order to install this fan in my TJ I had to “Snail Mail” an “in-the-box coupon” to get the required bracket needed to hold the overflow bottle. This took 11 calendar days to arrive. (Had I purchased this fan for $200 or needed it NOW I would have been a bit more ticked off.)

Third Impression:

This Sucks!

The passenger side bracket that holds the fan to the radiator does not provide clearance for the A/C Condenser lines. This required a 1-inch notch to be cut in the bracket. One would think they would notch all these brackets to start with.

Remember the recovery bottle bracket I waited 11days for?

The two boltholes in this bracket did not line up with the drivers side bracket that holds the fan to the radiator. Misalignment was better than 3/8 of an inch. (This is their bracket not lining up with their other bracket.)

In addition, this bracket was far too wide. Once I drilled the holes out so it would bolt on I found the bracket to be ¼ inch too wide. It was hitting the inner wheel well sheet metal.

I trimmed the width of the “snail mail” bracket down by ¼-inch.

All this bracketry appears to be laser cut. I would imagine it wouldn’t be too difficult to get it right. Nor was it that difficult to correct on my end, but….. That is indeed what I had to do.

The instructions that come with the unit instruct you to bend the radiator fins in a certain spot and then insert the fan temperature-sensing unit.

Nope! This isn’t true.

Apparently the Flex-a-lite folks updated the design, and the fan temperature-sensing unit is now mounted and incased on the fan housing, but someone forgot to change the directions.

I dislike things like this intensely. For what this thing cost, I would expect everything to fit and be right out of the box.

To start with it was safe to assume I was not exactly overwhelmed with a vision of quality here.

That said here are the results of my testing.


Testing Equipment:

As some of you know, I have a friend who owns an automotive testing lab with all kinds of testing equipment related to temperature recording. Over the last few weeks I have borrowed some of this equipement and performed the same tests on both the Mechanical Fan/Clutch and the Flex-a-lite II fan.

The equipment I used had one (1) in-fluid temperature sensor placed inside the upper radiator hose where it meets the radiator.

This sensor recorded time and temperature data, ever 3 seconds, to a small hand-held data collection device. All temperatures are in Degrees F and recorded to an accuracy of 1/10 of a degree F.


Types of Tests:

I performed three different tests on both the original equipment Mechanical Fan/Clutch and Flex-a-lite Electric fan over several weeks. Each setup went through these three tests multiple times.

At Idle Test:
This test measured the Highest and lowest coolant temperatures with the Jeep idling in my driveway for 15 minutes after a 5 minute warm up period.

Stop and Go
This test was a 6-mile stop and go, inner city drive, after a 5 minute warm up period. Obviously each test was not exactly the same as stoplights most likely did differ. But the course was indeed exactly the same each time. Max Speed was 25 MPH.

Highway:
This test covered a distance of 18 miles on Interstate 75. Nine miles down the interstate, off the exit, turn around and nine (9) miles back. Highway Speed maintained at 65 MPH.


Test Notes:
As I stated, each of these tests was conducted multiple times. The data I am sharing is the data I have for those days when the outside air temperature was the hottest. for each setup.

Also note, the outside air temperatures are different for each of these tests, and what was being tested, so please take that into consideration.

Air Temp = The outside air temperature range during the test

Highest = Highest recorded coolant temperature during the test.

Lowest = Lowest recorded coolant temperature during the test.

Average = Average coolant temperature of all recorded temps during the test. (This is not the average of the High/Low temps, but rather of hundreds of temps.)

Hi/Low Delta = The difference in degrees between the Highest and Lowest recorded temps.



Here are the results for these tests with the Air Conditioning OFF.

http://www.dana60.com/daless2/coolnac.jpg


At least as far as my testing efforts go in every case the electric outperformed the mechanical fan clutch. What is also interesting is the electric test occurred when the air temperature was five (5) degrees F higher.

However, interesting to note is the delta between high and low temps is slightly greater for the electric.

In support of the information Joe West posted about the inaccurate TJ water temp gauge, my gauge never moved past just touching the Zero on the 210 on the gauge face at any time during any of these tests.

Here are the results for these tests with the Air Conditioning ON.

http://www.dana60.com/daless2/coolac.jpg


Big difference here folks.

I think that is because the electric fan is on at all times when the A/C compressor clutch is engaged. Where as the mechanical fan clutch has no means of providing additional airflow through the radiator.

Also note, the electric fan has a thermostat that can be adjusted to tune the coolant temperature in.

Off Road Test

I did not think to test the coolant temps with the original mechanical fan/clutch, so I have no data to report. I did however record these temps with the Flex-a-lite fan.

I would not in any way call this hardcore off roading, but it wasn’t a cakewalk either. This temp data was collected during a 2.5 hour off road adventure, which covered 1.7 miles (about 0.7 MPH). Outside air temp varied from a low of 90 degrees F to a high of 97 degrees. F.

http://www.dana60.com/daless2/coolor.jpg


Current Impression:

OK, I’m impressed.

I was indeed surprised at the effects. In my mind, and at least as far as my testing has gone, this puller fan (2340 CFM) does indeed outperform the stock mechanical fan/clutch.

I cannot say I feel any difference in power as a result of this change.

I do believe there may be a minor improvement in MPG, but I do not have enough overall miles on it since this change to make this statement with any degree of warm fuzzy feeling.

I have no idea how well this setup will hold up over time. It does appear to be very well built but time will tell.


Hope some folks find this useful.

Frank


PS: I plan on installing a second, under dash coolant temperature gauge, as I just can’t live with the level of inaccuracy of the stock TJ gauge.

Data Mining

This evening I went over to Kevin’s lab to get some lesson in data mining.

The data I shared above reflected the coolant temperatures captured for one set of tests when the outside air temperature was the hottest. This was my attempt to show the worst case that I had collected.

All the testing I did occurred over a four week period, and each test was run multiple times. During this process the data collection unit I used literally recorded more then 100,000 data elements. Tonight Kevin helped me extracts some of this data and put it into what is hopefully a useful format.

In the tables below you will find averages for all coolant temps in any given test.

For example:
I ran the Idle Test without A/C five (5) times for the mechanical fan/clutch and seven (7) times with the electric fan. Time, Air Temperature, and Coolant Temperature data elements where captured every 3 seconds, during each 15 minute test.

The same was true of all other tests. Lots and lots of data here folks.




How to Interpret these Tables:

Lets look at The A/C OFF Mechanical Fan/Clutch information in the table below.

The average air temperature for all tests I performed in this category (A/C Off, Mechanical Fan/Clutch), on all the days I tested was 87.9 F.

The average coolant temperature for “All Idle Tests” on all days was 230.6 F.

To the right of the Average Idle Test coolant temperature you will see 3 columns labeled “+/- 2”, “+/- 3”, and “+/- 4” .

These columns give the Percent of all Temperatures recorded, for each test, which fell within Plus (+) or Minus (-) Degrees F of the Average.

For example:

Take a look at the Idle Test results line again.

The average Idle Coolant Temperature for the Mechanical Fan/Clutch was 230.6F.

The next column, ( +/- 2) is telling you that:
72.7 % of all coolant temperatures recorded for all Idle Tests where within 2 degrees of the average.

In other words,
72.7% of these temperatures fell between 228.6 F and 232.6 F.

(If 10,000 temperatures were recorded during all the tests in this category, 7,200 of these temperatures were within 2 degrees of the Average Temperature.)



The next column,
(+/- 3) is telling you that 86.3 % of all coolant temperatures recorded for all Idle Tests where within 3 degrees of the Average.

In other works,
86.3 % of these temperatures fell between 227.6 F and 233.6 F.

And so on.

I hope I explained that clearly. If not I will try again tomorrow.


Data Extract:

Here is the data extracted from all the coolant temperature data collected. Hopefully you will find it in a format that might generate some thought and questions, and perhaps even a revelation or two. I still need to study this to see what I might pull out of it.

http://www.dana60.com/daless2/deviatena.jpg


http://www.dana60.com/daless2/deviateair.jpg


Have fun, and let me know what you think.

Frank

:eek:

I think you need to take some of your free time and bend up a nice cage for me. Six point will be fine but I'd like eight, thanks :beer:

Frank,
Do you work for this friend of yours with the testing lab? Perhaps you should, you seem to have a pasion for automotive testing. ;)

I must say this is suprising. I have never heard of an electric fan out performing a mechanical fan. The mechanical fans on my vehicles move so much air (when they are engaged) they stir up dust underneath the vehicle. The electric fans I've seen do little more than make noise. What model is this fan and what are it's dimentions?

How does this fan do when you park and leave yout Jeep idleing with the A/C on? That's what it usually takes for my clutch fan to fully engage. I would be curious to know if it can keep your Jeep cool under that condition. Also, If not, how quickly does it cool down once you start driving again? I don't suppose you tried towing anything. That would be another test I would be curious about.

Hi Oliver,

My apologies for not responding to your questions any sooner. My availability lately has left a bit to be desired and I did not see your questions until just now.

I suppose your right, I do enjoy testing. I have a passion for getting down to the root of things as factually as I can, but I am certainly no professional.

I have to admit I was really surprised at the results this testing demonstrated. I was always of the school that the mechanical fan/clutch would be better at keeping things cool myself. And I have heard of many a war story about how poorly sometimes they can perfrom. But having won this Flex-a-lite 475 Electric fan kit during a Jeeping event I figured I would see what it could do. At the start of this I had only intended to test them both and then re-install the stock fan/clutch. (As I said, I was of the believe the electric would not perform as well.)

If you look at the original post, the second table from the top you can see the results of my testing with the Jeep idling for 5 minutes, with the A/C on, for both configurations. The electric clearly outperformed the stock fan/clutch as far as my testing went. What is also notable is that the outside air temp during the electric fan test was 4 degrees higher then the air temp for the mechanical fan clutch. I don't have any information for the A/C On, Idle temps for any period of time greater then 5 minutes. When I get some free time perhaps I will barrow the equipment and test this out farther.

I believe part of the reason the electric does so well with the A/C on is becuase the electric fan is always on whenever the A/C clutch is engaged.

If you look at all these numbers, across the board the Electric with A/C on outperforms the Stock Fan/Clutch with the A/C off for the limited testing I did.

So far so good with this set-up. Time will tell if it holds up, yet I am convinced, at least in regard to this particular electric fan, that it does indeed outperform my stock Fan/Clutch.

Sorry I don't have anything to offer on performance while towing as I don't tow with the TJ.

Have a great day,

Frank

I have one of these fans and it works great so far

Frank,
I had forgotten all about that post. I am still surprised you found the electric fan to be better. I don't think I'll be converting any of my vehicles to electric though. Let me tell you about an experience I had recently.

I was driving through Denver on a hot August day in my wife's Ford Explorer. There was an accident up ahead which created a 2 mile long traffic jam. While sitting in that traffic jam with the A/C going full blast, the Explorer began to heat up. I have no idea what the ambient temp was, but given that everyone around me was doing the same thing, I guessing it was well over 100 at the radiator. Idleing was clearly not enough even with the clutch fan fully engaged. I was able, however to kick up the idle a bit by giving it some gas, which not only stopped the temp from going up but actually began to cool it a bit, all without turning off the A/C. When we did start moving, I used lower gears to maximize the fan speed. This also helped tremendously. The fan sounded like an air turbine it was moving so much air. Once we started moving at reasonable speeds, it cooled off rather quickly and we had no more problems. I don't think an electric fan would have been able to do any better, and of course, there is no reving the motor to speed up the fan with an electric.

It sounds like you have kept your electric fan installed. Have you run into any situations such as that? Obviously I have no scientific data like you, but based on that experience, I will be keeping my clutch fan. Not trying to debate you or anything, just giving my opinion on the subject.

Caculating the varraiance between the means of each type of test may be interesting way to compare mech to elect...

Originally posted by Grandpa Jeep
Frank,
I had forgotten all about that post. I am still surprised you found the electric fan to be better. I don't think I'll be converting any of my vehicles to electric though. Let me tell you about an experience I had recently.

I don't think an electric fan would have been able to do any better, and of course, there is no reving the motor to speed up the fan with an electric.



I disagree with your example. I run electric only in a pusher configuration (permacool 14 in., 2,950 cfm, electric fan). Since the electric operates at a steady 1800 RPM, you don't need to rev up the motor to get it to push the max amount of air, it works just fine at an 800 rpm idle.

Originally posted by oldjeep


I disagree with your example. I run electric only in a pusher configuration (permacool 14 in., 2,950 cfm, electric fan). Since the electric operates at a steady 1800 RPM, you don't need to rev up the motor to get it to push the max amount of air, it works just fine at an 800 rpm idle.

Chuck,
The way I read Franks results, the electric fan was compareable, and actually a little better than the mechanical clutch fan at idle. Rev the motor up to 1600 rpm and see which one moves more air. The stock fan on both my Mustang and Explorer will blow leaves and dust out from under them if you rev the engine at all with the fan engaged. I have yet to see an electric fan that will come close to that. Maybe you have never needed that kind of air movement and maybe you never will, (my Jeep did fine with a 2 blade fan out of a plymouth turismo:eek: ) but I'll keep my clutch fan for those trips through Denver.

Originally posted by Grandpa Jeep


Chuck,
The way I read Franks results, the electric fan was compareable, and actually a little better than the mechanical clutch fan at idle. Rev the motor up to 1600 rpm and see which one moves more air. The stock fan on both my Mustang and Explorer will blow leaves and dust out from under them if you rev the engine at all with the fan engaged. I have yet to see an electric fan that will come close to that. Maybe you have never needed that kind of air movement and maybe you never will, (my Jeep did fine with a 2 blade fan out of a plymouth turismo:eek: ) but I'll keep my clutch fan for those trips through Denver.

The permacool that I use has the same 14" flex fan blade that they use on their clutched fans. I agree, the crappy plastic electric fans don't move the air as well. Mine creates a dust cloud when running (even when the engine is not running;) and sounds like a B52 getting ready for takeoff:D The flex-a lite that he is testing with is inferior to the high performance permacools

I'll have to look into that one. I haven't seen to many that will do much more than make noise and create a gentle breeze. How thick is it? My radiator is right up against the headlight buckets. Is that how yours is?

Hi Oliver,

One of the things I can count on is enjoying a legitimate conversation with you here. I appreciate that.

Obviously there are variables involved in all of this. In your case your altitude may very well be a contributing factor. I would think thinner air would have less heat transfer abilities but I don't really know that. Also, if I'm not mistaking water boils a about 10 to 15 degrees less at one mile high.

Setting the altitude aside though the cooling fan and the volume of air that goes through it is only one of two major factors.

The other factor, as you pointed out in your experience is coolant flow.

I would think by revving the engine the coolant flow out of the engine into the radiator increased, thus giving the coolant a greater opportunity to be cooled in the radiator and by the air flow through the radiator. Does that make sense?

How much of this can be attributed to coolant flow and how much to fan efficiency I have no clue, but I would think both are significantly involved.

Just a thought.

Frank

Frank,
You're right, I didn't consider altitude. It stands to reason that thinner air would have less mass and therefore less cooling ability than air at lower altitudes. I would think this would tend to require more airflow and would really stress the need for a good fan. Perhaps if you ever come out here we can really put that fan of yours to the test.:D

My own experience has shown this to be true. My wife used to have a '91 Camaro with a 305 and an electric fan. The A/C was unuseable in stop and go traffic as it would cause the engine to overheat. On a really hot day you had to crank up the heater. The cooling system was otherwise clean and in very good shape, but that fan just couldn't keep it cool. My 5.0L Mustang on the other hand was similar in just about every respect except it has a mechanical clutch fan. I have never had a problem with it overheating or even getting hot unless the coolant level was below about 1/2 full.

FWIW, water boils right at 200* on my kitchen stove according to my handy dandy radio shack digital thermometer. However, I don't think that would be as much of a factor in a pressurized cooling system unless it actually did cause it to boil.

I also did not consider the additional flow due to the faster speed of the water pump. Perhaps the next time you are out with your friend's testing equipment you can see what effect that has. I would be interested to see the results as I have heard that there is an ideal rate for maximum heat transfer. I'm guessing it will occur right at cruising rpm, but you never know, it might be more optimized for lower rpms. Anyway, good to hear from you.

Originally posted by Grandpa Jeep
I'll have to look into that one. I haven't seen to many that will do much more than make noise and create a gentle breeze. How thick is it? My radiator is right up against the headlight buckets. Is that how yours is?

It's 3.75" thick. My radiator is a stock 2a radiator in the stock location. My fan is set up as a pusher, I havn't got the space to use it as a puller. My motor is pushed forward as far as possible.