Electric vs Mechanical fan cfm

thermorex · **Posted:** Mon Jul 07, 2014 12:55 pm

You'll run into clearance issues with the stock shroud. Plus, there isn't a bigger than 17 inch e-fan as I know, and I believe the diameter of the shroud is about 20 inch or more.

jrsavoie · **Posted:** Mon Jul 07, 2014 1:05 pm

thermorex wrote:

You'll run into clearance issues with the stock shroud. Plus, there isn't a bigger than 17 inch e-fan as I know, and I believe the diameter of the shroud is about 20 inch or more.

Mounting a smaller than diameter fan in the shroud should not present a problem. What are the clearance issues?

I'm thinking running supports across the shroud at the proper depth to mount the fan to and leaving the area around the fan as is.

Or, if necessary making a round block off plate to shrink the diameter of the shroud.

thermorex · **Posted:** Mon Jul 07, 2014 2:26 pm

Sure, if you do all that work, it should work. But you should also consider adding some rubber flaps, to open a gap in that block off plate, so on higher speed the modified shroud won't act as an air blockage. Most shrouds for e-fan have them for that reason. Let us know how the mod process goes, I'm curious what you come up with.

jrsavoie · **Posted:** Mon Jul 07, 2014 2:33 pm

I was thinking more along the lines of eliminating the block off plate. Just letting the extra air go around the fan.

Just attaching structural mounting to the fan shroud and hanging the fan mid air. I could use the biggest fan available.

thermorex · **Posted:** Mon Jul 07, 2014 2:56 pm

As further away the fan goes from the radiator, the efficiency decreases. As much empty space is between the shroud and the fan, the efficiency decreases. The eBay shroud is smaller than the radiator, but at least forces the air flow through all its area. The sides that aren't covered on the radiator are used as an air escape way (behaving like rubber flaps). I think that hanging the fan centered on the shroud hole would give you the equivalent of mounting the fan on the radiator at best. I did try a 14 inch fan a while ago, mounted on the plastic oem shroud and I didn't like it.

PZKW108 · **Joined:** Sun Apr 06, 2014 5:23 pm **Posts:** 461

I'm running a flex a lite black magic 15", it come with a really nice shroud with a thick rubber seal that perfectly fit and cover the FULL area of the rad.

I didn't like the flex a lite controller that goes thru the rad so I bought a Derale High Amperage Adjustable Dual Electric Fan Controller with a 3/8" NPT Thread In Probe.

it seem to work great for the few miles I drove before I had an problem with an injector.....

this fan is advertised at 3300 cfm, but the most important thing is to get the flow thru the rad and this one seal really good

let you know when its back on the road !! :JEEPIN:

thermorex · **Posted:** Tue Jul 08, 2014 5:33 am

PZKW108 wrote:

I'm running a flex a lite black magic 15", it come with a really nice shroud with a thick rubber seal that perfectly fit and cover the FULL area of the rad.

I didn't like the flex a lite controller that goes thru the rad so I bought a Derale High Amperage Adjustable Dual Electric Fan Controller with a 3/8" NPT Thread In Probe.

it seem to work great for the few miles I drove before I had an problem with an injector.....

this fan is advertised at 3300 cfm, but the most important thing is to get the flow thru the rad and this one seal really good

let you know when its back on the road !! :JEEPIN:

Would you mind posting a link, or the part number?

PZKW108 · **Joined:** Sun Apr 06, 2014 5:23 pm **Posts:** 461

15-inch Black Magic Xtreme S-Blade reversible electric fan with adjustable thermostat controller
Part Number: 180

thermorex · **Posted:** Wed Jul 09, 2014 7:08 am

PZKW108 wrote:

15-inch Black Magic Xtreme S-Blade reversible electric fan with adjustable thermostat controller
Part Number: 180

Thanks a lot!

omaharacer · **Posted:** Thu Jul 17, 2014 4:20 am

Reposting this here as more people browse the regular forum than the "tech" one. I finished installing the same kit from eBay. Unfortunately I bought the normal auction w/ the relays, then the variable speed controller on top of that from Summit so my overall price was a little higher.
Gas V6 fan w/ Hayden HD clutch, lower half of shroud removed "stock"

Mechanical fan/shroud removed

FFD Fan mounted

I used the push-through universal zip-tie things to mount the fan. I also mounted it as far to the driver side as possible to help clear the mechanical fan pulley/mount (barely cleared by 1-2mm anyways). I had previously removed the factory air box and made a "warm" cold air intake w/ 3" exhaust pipe and an AEM dryflow filter so I had plenty of mounting room for the control box. I used 12v key on signal wire from the pink/white MAF sensor pigtail, and pulled the low-speed relay (keeping high-speed relay in) to check to see which blue wire (two identical blue wires from a/c condenser pigtail) went to the front a/c condenser fan (front fan gets high coolant temp for low, and a high speed for a/c use) and used that for the signal wire for a/c on. (This allows the radiator fan to turn on when the A/C is on) I then re-inserted the low-speed relay - to which it isn't going to anything any more. For ground I just used an upper radiator support bolt next to the fender.

Everything all taped up. I re-installed the top half of the factory fan shroud to hide the power wire from the fuse block (inline 30A fuse). Also to help keep airflow flowing through the condenser/intercooler/radiator since it covers the top gap. Helps hold down the coolant overflow as well.

HUGE empty area where the front A/C condenser fan used to be. Factory fan bearings decided to fail, thus pulling more than 40A through the factory wires and blowing the $5 fuse. Front fan hasn't worked for some time, no overheating issues prior to this fan install and a/c seemed to work ok despite that - at least while moving. Having that fan out of the way will definitely open up air flow, and a functional puller fan when the a/c is running will probably give colder temps too. I removed "broke out" all of the thin plastic divider/mini-grille sections - this was mainly because I couldn't get the grille out since the ARB bumper/winch was in the way and I didn't want to break out the engine lift to take it off. I think it gives the front end a little cleaner look now - except for the trans cooler.

I have the controller set to the coldest position right now and in the 75* weather with "spirited" driving, the temperature gauge never went past normal/half mark. The fan will also run for a little bit AFTER you shut off the engine. My EGR/cooler is removed along w/ the cooler lines. That should help a little with coolant temps allowing a slightly less CFM fan to be used (unknown exactly how much removing cooler lines from system will help though).

thermorex · **Posted:** Thu Jul 17, 2014 9:20 am

Nice, I updated the tech forum with a post. BTW, Did you tried to raise up the temperature of the thermostat, so the fan would start a bit later? Mine is not all way at the minimum, not sure what is the temperature but the engine temp is good.

GreenDieselEngineering · **Joined:** Sun Jun 07, 2009 5:10 pm **Posts:** 1111

Can this fan be wired directly to the vehicle wiring using the pusher fan wiring? Would it operate fine with the stock low and high relays? The separate controller seems to allow fine tuning, just wondering if using stock wiring is feasible?

omaharacer · **Posted:** Thu Jul 17, 2014 5:01 pm

Theoretically... yes. You could directly wire the fan to the front pusher wires. It may pull too many amps w/ both fans going though as the "Radiator" fuse is 40 amps. I thought about doing just that since my front pusher fan was being taken out anyways, however I didn't like the idea of not knowing when the fan would be turning on. It would have saved a little wiring and the relays wouldn't have been needed. You could always buy the "kit" without the relays on eBay and wire it up like that and let us know.

-*Edit* - Now you got me thinking again.... The factory radiator fan programming SHOULD turn on at the correct temperature, as will the A/C. I'm going to go outside and disconnect the controller and just attach it to the factory pusher wiring and see what happens. I have an infrared thermometer I'll check it with. Be back in a little bit.

thermorex · **Posted:** Thu Jul 17, 2014 5:24 pm

This fan has only 2 wires, so it's only a 1 speed. Stock pusher has 3 wires, 2 positive and a negative, each positive being for a different speed (if I remember correctly).

The only way I can see it work with the stock fan wiring would be to measure the resistance of the variable speed controller thermostat when it starts at 60% and when is in full 100% speed. Then, using the stock wires for pusher and some resistors, the variable speed controller would command the new fan unit on different speeds (so we still use the variable speed controller). I'm sure Keith can program the stock wires to start the fan at whatever temperature he wants, but I am not sure how a one speed fan can run in 2 speeds, without altering the voltage... But I may be missing something.

thermorex · **Posted:** Thu Jul 17, 2014 5:31 pm

If using the variable speed controller, the only way the stock wires can be used with it is to connect the Ac wires to the variable speed controller, there are 2 Ac designated ports for it. Since the manual always on/off operates on negative and not on positive, stock wires can't be used to command the variable speed controller to turn the fan on/off, unless some other "hacks" are performed.

omaharacer · **Posted:** Thu Jul 17, 2014 6:12 pm

These are my results

Using the infrared thermometer pointed at the hottest area of the radiator I could find w/ the top half of the shroud still on - The fan turned on around 200* (just prior to middle of temp gauge) and shut off around 175*. Fan will turn on when a/c is on at any temp.
All I did was use the front pusher wiring. Both blue wires (one for temp relay, one for a/c relay) joined together and to the positive lead on the fan. The negative lead on the fan went to the black negative on the pusher wiring pigtail.
Since my 40amp fuse blew from the failing OEM pusher fan (and they cost $5 each), I used the 30amp fuse from the light bar (that my jeep doesn't have).
I'll leave the variable speed controller there for now in case I want to change back. But as of now it appears that the factory ECU will control the fan just fine, just without the "variable" speed.
I have no way of knowing if the fuse will blow w/ the pusher fan going at the same time since I don't have a good one to test with.

mass-hole · **Posted:** Thu Jul 17, 2014 8:03 pm

thermorex wrote:

This fan has only 2 wires, so it's only a 1 speed. Stock pusher has 3 wires, 2 positive and a negative, each positive being for a different speed (if I remember correctly).

The only way I can see it work with the stock fan wiring would be to measure the resistance of the variable speed controller thermostat when it starts at 60% and when is in full 100% speed. Then, using the stock wires for pusher and some resistors, the variable speed controller would command the new fan unit on different speeds (so we still use the variable speed controller). I'm sure Keith can program the stock wires to start the fan at whatever temperature he wants, but I am not sure how a one speed fan can run in 2 speeds, without altering the voltage... But I may be missing something.

I believe what I had read was that the pusher fan has two separate coils of wire. when one is powered, it runs at low and when both are powered it runs high. That is why there are two positive leads in the plug. They can activate one or both. If you power the radiator fan off the low one it should come on whenever the fan is requested. If you put it on the high speed pin it will only come on when hi-speed is requested.

thermorex · **Posted:** Thu Jul 17, 2014 10:19 pm

mass-hole wrote:

thermorex wrote:

This fan has only 2 wires, so it's only a 1 speed. Stock pusher has 3 wires, 2 positive and a negative, each positive being for a different speed (if I remember correctly).

The only way I can see it work with the stock fan wiring would be to measure the resistance of the variable speed controller thermostat when it starts at 60% and when is in full 100% speed. Then, using the stock wires for pusher and some resistors, the variable speed controller would command the new fan unit on different speeds (so we still use the variable speed controller). I'm sure Keith can program the stock wires to start the fan at whatever temperature he wants, but I am not sure how a one speed fan can run in 2 speeds, without altering the voltage... But I may be missing something.

I believe what I had read was that the pusher fan has two separate coils of wire. when one is powered, it runs at low and when both are powered it runs high. That is why there are two positive leads in the plug. They can activate one or both. If you power the radiator fan off the low one it should come on whenever the fan is requested. If you put it on the high speed pin it will only come on when hi-speed is requested.

I see, makes sense, thanks! Still not sure why would anybody use the stock wiring, just to save some $$$ w the speed controller? I think that controller is best in protecting the charging system, not only to start the fan. But it definitely opens up more options. I'd be using the variable speed controller and the stock wire connected to the Ac wire on the controller, this way the stock temps are still used.

As I know, the pusher starts at 205 engine temp, but I may be wrong again... At that temp it's a little too late to start cool the radiator.

Would be cool if Keith can change the temp to start cooling the radiator at 180-ish, I wonder if that's possible though, don't think the rad has a temp probe.

flash7210 · **Posted:** Fri Jul 18, 2014 9:02 am

Yes, the stock pusher starts at about 205 deg F and turns off at just below 190. (A/C off)
Its seems to do just fine cooling the engine that way. It did for my testing but that was
just idling in my garage and with the mechanical fan removed.

Ideally, the fan should come on at 2 to 3 degrees above the thermostat opening temp.
So, if you have a 195 deg t-stat, then the fan should come on at about 198.

This morning it was about 80 degrees outside. My engine temp never got above 197 and the
electric fan never came on (I have a 195 t-stat and my mechanical fan has been removed).

Of course, the electric fan is always on with the A/C on.

thermorex · **Posted:** Fri Jul 18, 2014 9:19 am

That's good to know, now all we need to know is how it would heat up when towing. I have tested my setup with about 2k tow, it was perfectly fine, but 2k towing is nothing for crd...

Electric vs Mechanical fan cfm

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