Performance Electric Radiator Fan Options

[child9]

^ this.

The more I look at it, the more I am leaning towards the math. OEM clutch fans simply move a LOT more air than electrics. This means they do more work, cool better (unless at idle), which means they require more power. I suspect the power-to-rpm relationship is very similar to that of drag, being exponential in nature. The electric fans do less work and hold a constant rpm and therefore require less power to run. Conversely, the OEM fans cool better (unless at idle) due to significantly higher CFM.

Personally I would run an OEM clutch fan if I could. In fact now that I just wrote all that, I'm going to revisit fabricating a new fan shroud that will mate the stock 2JZ clutch fan to my Jeep radiator. (I use the term "mate" loosely)

 

[child9]

It is fairly well known the mechanical fans add rotational mass and drag to the engine
http://www.carcraft.com/howto/ccrp_0707_high_performance_cooling_system/viewall.html

Since peak HP usually occurs near peak rpm, I am not surprised. For a racing vehicle the electrical choice is obvious. The mechanical fan isn't pulling 35 HP the whole time, but it sure was on that car in the Car Craft example at peak rpm/power. This follows what I mentioned regarding the HP requirement of the mech fan rising exponentially with engine rpm as well. IF your vehicle doesn't require 35 HP worth of air flow to keep it cool under max power/ max load, then speccing an electric system that can still manage the cooling requirements will allow that power difference to be put to something else...like the wheels.

Summed up, I think it should be understood that an electric system may not flow as much CFM as a mech fan assembly, but that total flow from the mech fan is likely not required and so an electric setup that flows less yet still flows adequately for the engine in question will draw less power and net more HP to other systems. Racing is about pushing limits for another 100th of a second...so exchanging cooling system "breathing room" for whatever HP that will net is going to happen among those guys. Racers take risks by reducing margins of error in various systems all in the pursuit of a better ET. "Better" defined by racers is not going to be "better" as defined by a "Mr. Conservative" or a "Mr. Reliable Workhorse."

 

[child9]

You know this same situation applies to anything in the engine that does "work." Take the water pump for example. You can replace that with an electric pump. If the electric pump is variable speed, then using some simple thermocouples you could adjust the coolant flow rate to yield the most dramatic temp drop across the radiator. Too slow and the input temp will climb. Too fast and the output temp will climb toward the input temp. The ideal flow speed will have the input temp be normal and the output temp as low as possible. This would allow the pump to be driven at a constant speed, instead of the mechanical pump also behaving like the mechanical fan and requiring more HP with more RPM.

 

[lazyxj]

It is fairly well known the mechanical fans add rotational mass and drag to the engine
http://www.carcraft.com/howto/ccrp_0707_high_performance_cooling_system/viewall.html

So does the flywheel and alternator, ready to get rid of them?

Electric fans can work great but they do add a lot of complexity to the cooling system, and use parts not necessarily available at the Napa store.
We travel long distances in the XJ and like being able to readily source repair parts when needed. Fan clutches are available most anywhere.
A couple of horsepower, one way or another, isn't going to change my driving experience nor is the possible fractional increase in mileage, if any.
Once again I see a lot of claims but no verifiable test data.

Plenty of highly experienced forum members use the stock mechanical fan. Here is a what Goatman, probably Naxja's most respected and experienced member, has to say about it.
"It has been proven over and over again that an XJ cooling system in good working order works just fine, even with lifts and bigger tires"
http://www.naxja.org/forum/showthread.php?t=1009479&highlight=cooling&page=2
Cooling systems are lot more than just the fans. Electric fans are very appropriate when there is no room for the mechanical fan or for use with a remote radiator.

 

[GordoSmasho]

Does anyone know what type of fans the DBO kit comes with? It would seem crazy that his kit pulls "4,336.23" CFM and only drawes 18amps. How is that possible. The dual fan kit listed about pulls 50 amps to do 4000 CFM. I don't have an issue with my kit just wondering how that is possible?

 

[bigdaddyjlove]

Some toyotas and at least one model of grand Cherokee ran hydraulic fans powered by the ps pump. Gets the large moment angle fan decoupled from the engine. This is important on a high rev motor like yours. Power output is more efficient with direct drive hydraulic rather than generate electricity move it through switched and relays and turn a relatively inefficient electric motor.

Just an interesting idea. I grabbed one of the p.s. pumps with dual outputs off of a WJ at thr junkyard with ideas about a hydraulic winch, or maybe a hydroboost brake system. Due to project bloat, neither has happened.

 

[Alexia]

Does anyone know what type of fans the DBO kit comes with? It would seem crazy that his kit pulls "4,336.23" CFM and only drawes 18amps. How is that possible. The dual fan kit listed about pulls 50 amps to do 4000 CFM. I don't have an issue with my kit just wondering how that is possible?

Here is their testing using an air flow meter.
http://www.naxja.org/forum/showthread.php?t=1057920
http://www.naxja.org/forum/showpost.php?p=245272123&postcount=14
http://www.naxja.org/forum/showpost.php?p=245275675&postcount=21

The fan blades on their fans are much lighter and have less overall depth. It is a really noticeable difference in weight compared to the stock electric fan. Less weight means less energy to turn them.

 

[child9]

You just reminded me...the Japanese 2J from an Aristo has a hydraulic pump. I replaced it with a US pump and now it's belt driven. I have one in the garage. I will investigate this further. Ha.

 

[Digger87xj]

Here is their testing using an air flow meter.
http://www.naxja.org/forum/showthread.php?t=1057920
http://www.naxja.org/forum/showpost.php?p=245272123&postcount=14
http://www.naxja.org/forum/showpost.php?p=245275675&postcount=21

The fan blades on their fans are much lighter and have less overall depth. It is a really noticeable difference in weight compared to the stock electric fan. Less weight means less energy to turn them.

Doesn't make it any more believable.

Don't get me wrong, I can't dispute the numbers but I can question them. The fans seem to do great in town and low speed driving but when I pull a hill or even extended highway driving they just can't draw enough air.

experienced it worse with the 4.0 than the 5.9

 

[Alexia]

Doesn't make it any more believable.

Don't get me wrong, I can't dispute the numbers but I can question them. The fans seem to do great in town and low speed driving but when I pull a hill or even extended highway driving they just can't draw enough air.

experienced it worse with the 4.0 than the 5.9

You should check your cooling system then. The DBO setup is having no issue holding 200º F to 210º F in my MJ with a fresh cooling system while speeding along the highway and heading daily over the mountains here in 95º F weather.

 

[Digger87xj]

Thanks for the tip

 

[jeeperjohn]

It holds to reason that in order to move more air you must apply more power. Therefore those companies that advertise their fans only draw so many amps have fans that only pull so much air. If you want high airflow you have to use up more power getting it, either by a higher amp motor or by drawing more power from the crankshaft. The engine driven fan clearly moves more air than any electric setup on the market. If you can't use an engine driven fan for some reason then you can get an electric setup that comes close to the engine driven fan in terms of airflow but it will cost a lot of money and possibly require some modification of radiator placement.

 

[yossarian19]

JeeperJohn - I think you are ignoring the effects of fan blade design. As an extreme example, a fan with three 3" wide steel blades with a crappy pitch angle will pull a lot less CFM per amp than a 10-blade plastic S curve fan. So while more amperage should, all else being equal, equal more CFM - in reality, there are differences between fans that will change their power / cfm efficiency.

 

[Digger87xj]

Well I went ahead and ordered the Derale 16928 high output fans from Jegs...

Derale#259-16928

High-Output Dual Fan Assembly 4000 cfm
24.8 Amp Draw per Fan
28-1/2" W x 13-7/8" H x 3-1/4" Thick




I'll report on effectiveness after the install.

 

[techno1154]

Well I went ahead and ordered the Derale 16928 high output fans from Jegs...

Derale#259-16928

High-Output Dual Fan Assembly 4000 cfm
24.8 Amp Draw per Fan
28-1/2" W x 13-7/8" H x 3-1/4" Thick




I'll report on effectiveness after the install.

That is the set I have installed since 2004. I am quite happy with them. However, they are not a drop in install. A bit of fabrication will make them a worth while investment. I did replace most of the 14AWG wire that came with them with some 10AWG and used a pair of high AMP relays. I actually have both the fans on independent circuits with their own 30AMP fuse. Also, keep in mind that the OEM 90 AMP alternator will have to be replaced sooner than later.

Let us know how it turn out for you.

 

[Digger87xj]

Already have the 130A. alty... and the wiring to handle it.

No troubles with the fabbing..

Question for you.. Are they truly 3-1/4 thick?

 

[techno1154]

Already have the 130A. alty... and the wiring to handle it.

No troubles with the fabbing..

Question for you.. Are they truly 3-1/4 thick?

Yes, they are. Actually, Derale site have them listed as 3 1/2".

 

[child9]

JeeperJohn - I think you are ignoring the effects of fan blade design. As an extreme example, a fan with three 3" wide steel blades with a crappy pitch angle will pull a lot less CFM per amp than a 10-blade plastic S curve fan. So while more amperage should, all else being equal, equal more CFM - in reality, there are differences between fans that will change their power / cfm efficiency.

I partially agree with this. As I understand it, fan blade design affects the efficiency of the fan as a system to move air, that is true, HOWEVER it does not allow for the fan system to do more work than the energy it takes from the engine. No blade design can make a fan do more work, it can only increase the system efficiency thus allowing the fan to not waste as much of the energy being used to turn it.

1 HP is around 700+ watts...and some of these fans are 80 watt (like the DBO fans).

In the electric/electric comparison, the motor will not be able to do more work because of a more efficient fan blade...the more efficient fan blade will actually have to spin slower than the inefficient fan making the air moved equivalent. Regardless of the rpm the fan blades are smashing into air molecules and it requires work to move the air. More air pushed, more work done, more amps drawn (or higher voltage used).

Ultimately there is a theoretical maximum amount of air that can be moved by a 100% efficient fan motor and 100% efficient fan blade at a certain wattage. I DO agree that replacing a 50% efficient fan blade with a 75% efficient fan blade on the same motor will move more air while using the same amount of power...but it's only because it is losing less...which I guess is more or less what you said, Yossarian.

Jeez I can say a lot without saying much of anything, lol.

 

[Digger87xj]

'nother words

A more powerful motor coupled with a high efficiency blade = more CFM per unit of work

That's a good thing, no?

 

[Prom3theus]

Re: Re: Performance Electric Radiator Fan Options

Does anyone know what type of fans the DBO kit comes with? It would seem crazy that his kit pulls "4,336.23" CFM and only drawes 18amps. How is that possible. The dual fan kit listed about pulls 50 amps to do 4000 CFM. I don't have an issue with my kit just wondering how that is possible?

They use procomp 10 inch fans, also available on ebay through their ebay store. My dbo shroud at least came w procomps.

Regarding how is possible to get so many cfms... all you need is an anemometer ($10-ish from ebay), measure the wind speed a fan can pull the air with, and then multiply it with the total fan area (big circle area minus motor area). A "real" cfm though should factor the other obstructions in front of the fan, such the condenser, trans cooler, winch, etc. I am not sure how dbo performed the tests, but a plain math I've done a while ago, revealed the cfm of one 10 inch fan w/o restrictions to be around 2000 cubic feet per minute (dont remember exactly).

Side note, I also havent had a cooling issue w dbo fan bar, I run 2 fans (sides) on a variable speed controller and the 3rd (center) from a switch. Center fan also cools most of the trans cooler mounted in front. Knock on wood, this setup has been running great so far.