Engine driven vs. electric fans

quickbiker · Post by **quickbiker** » Sat Oct 28, 2006 9:43 am

I just read in 4x4 Garage magazine that the largest electric fan would still not cool as good as a mechanical fan. Just a tidbit fwiw. That mag is great, nothing but techy garage fixes and info. I think it only comes out once a year, and it's packed.

Post by **HenryJ** » Sat Oct 28, 2006 9:54 am

quickbiker wrote:I just read in 4x4 Garage magazine that the largest electric fan would still not cool as good as a mechanical fan.

While not a false statement, it may be a bit misleading.

An electric fan can exceed the CFM of an engine driven fan at low to idle engine speeds.
Crawling the desert I need the increased CFM that the electrics provide at low engine speeds.
The AC is a good indicator of the increased heat transfer. Mine stays colder since the electric conversion.
I really didn't make the change for the increased low speed cooling. I did it to better match the lowered cooling system temperature I want to maintain.

I will not dispute the fact that the engine driven fan can and will move more air at speed. There is no way an electric can keep up. A clutch fan really does a pretty good job of providing performance.

The electric is much more adjustable and versatile, IMO.

quickbiker · Post by **quickbiker** » Sat Oct 28, 2006 10:03 am

Just to make sure your tests are accurate, are you sure your stock clutch fan was at it's peak efficiency or was it wearing out. Mine was gradually running hotter and hotter, then I replaced my fan at about 60-70k miles, can't remember exactly when, but it cools awesome now, never gets above the normal 195.

F9K9 · Post by **F9K9** » Sat Oct 28, 2006 10:11 am

Mine had under 1k on it the first summer and the stock fan didn't cut it. Especially bad in heavy construction traffic and just sitting. I'm definitely glad I made the switch.

crew cab sonoma · Post by **crew cab sonoma** » Mon Oct 30, 2006 6:50 am

while i dont think that most commonly used electric fans can deliver the ammount of air that a clutch fan can, especially at anything above idle speeds.

but i do believe that electric fans are capable of delivering a more than adequate ammount of flow for most conditions. the stock clutch fans are designed for "worst case" conditions, such as max weight towing up long, uphill grades at 100+ deg. weather, with A/C on... and deliver more airflow than is needed more than 99% of the time...

quickbiker · Post by **quickbiker** » Mon Oct 30, 2006 8:44 am

I guess it really does depend on specific situations. The only time mine really gets above like 200 is if I am hauling a trailer up a very long steep hill.

killian96ss · Post by **killian96ss** » Mon Oct 30, 2006 2:13 pm

My stock mechanical fan clutch stays locked up in weather over 90°, roars like a jet engine and keeps the temperature around 220° .

I would happily trade my stock fan for an electrical fan set up like Brule or Reed has on their Crew Cab.

Steve

F9K9 · Post by **F9K9** » Mon Oct 30, 2006 2:48 pm

I recently (yesterday) read about a Lincoln(I think) set up that pulls something like 5000 cfms that a lot of the hotter setups are running. Traffic, 90° plus temps and the stock oem fan didn't cut it for me.

I admit that allot of my bias is from 12 years as a K-9 handler and leaving the rig running in high temps was a major concern when my partner was inside. I was always concerned about the AC failing or the engine failing. I never ran e fans in those rigs but, police packages have some added features to help. I was always in search of shade and I would open the hood when I had to leave the truck running. Bottom line is that when you have to idle, e fans is the only route in warm temps with the basic S-10 IMO. OEM fans work much better when moving than the e fan setups.

Edit, I corrected the suspect "Lincoln" efan set up from 500 cfm to 5,000 cfm.

2kwik4u · Post by **2kwik4u** » Mon Oct 30, 2006 3:22 pm

You guys crack me up.....All following factors are used for illustration purposes only.

What 95% of the people miss is the CFM required to cool the coolant in the radiator to a level in which it can accept more heat from the engine. Any more CFM than that is "wasted" so to speak.

Lets say that a stock fan pulls 2500CFM at idle and 5000CFM at 5,500RPM. Lets now say that an Efan pulls 3,800CFM constant. Lets also say that at 35mph, the truck moves 4,000CFM across the radiator by natural means. The point of all that? It most likely only takes 2,200CFM to keep the truck cool in all but the highest heat. So ultimately any of those solutions will keep the engine cool. Moving 35mph, having the efan running, or have the clutch fan on there.

My point being that if you put a lower temp thermostat in there, 9 times out of 10 the temps will drop, regardless of what fan you have, and in the end it's what you feel most comfortable running that will dictate what you choose to have on your vehicle. The statement that a crank fan will always cool better is an outright BAD assumption. There are a myriad of things that need to be considered such as engine compartment space, radiator core size, coolant flow rates, the time the coolant spends in the radiator, and average vehicle speed. One should take those into consideration, and choose accordingly.

I personally despise the parasitic loss of the clutch fan, the air-raid sound of the clutch-fan, and the lack of low speed CFM. I'm an Efan guy, and you'll be hard pressed to convince me otherwise.

quickbiker · Post by **quickbiker** » Tue Oct 31, 2006 10:22 am

Guess everyone has their needs. Now in a sports car, I wouldn't have it any other way than an Efan. The last thing ya want is drag of the fan off the start and cutting your high rpms. I'd just rather the engine do the work than cutting into my battery juice when winching. At low crawling rpms, the battery needs all the recharge juice it needs rather than running a high amp efan. Also, most of the time when I see a cooling prob on the trail, it's someone with an efan setup. I never worry about my clutch fan, I can see replace it when I see it start to degrade, before it's too late.

I really liked the efan I had in my camaro. And in something driven on the road, even if something in the efan circuit breaks, big deal, just keep it moving, even on a hot day, you can make it home. But on the trail, rock crawing, you may as well, hang it up.

Post by **HenryJ** » Tue Oct 31, 2006 11:05 am

If the stock clutch fan was available in a lower operating temperature range , I might have considered it.
Stock they just lock in way too late for desert crawling.
The stock operating temperature is good for emissions, but poor for performance and engine life. It is just too close to the edge.

Speaking to fan failures, I have seen more mechanical fans fail, than electric. Clutches, leaks, broken or bent blades.
Personally I have repaired or replaced more mechanical fans than electric.
Twin fans reduce the chances of a complete failure. What are the odds of both motors failing? Relays and fuses can fail. Spares are a good idea. Planning an easy bypass is a good contingency plan as well. I can think of a dozen ways to get an electric fan working again. When a mechanical fan fails there is rarely a "trail fix", other than removal.

The electric fans do require upgrading the alternator. That will benefit the system while winching as well. The addition of a winch would be a good reason to upgrade the charging system as well. Keep in mind that the charging system does not have as much effect on available power as the battery does. Granted a good alternator will recover the battery quicker and with less stress on it, but really under heavy loads the battery provides to reserve needed to meet the demand. Rarely do people have an alternator that will meet the draw of a warm winch at maximum load.

All things taken into consideration, I think there are more advantages to a good electric fan.

If the stock fan meets your needs, why fix what is not broken? The stock fan did not meet my needs. I really did try to find one that operated at a lower temperature. Had I found one, perhaps it would work for me. I do like the faster warm ups and other advantages that came with the electrics though.

Snoman002 · Post by **Snoman002** » Tue Oct 31, 2006 1:38 pm

Do these clutches have the thermostat on the front like most clutches? Can you modify the thermostat to engage the fan earlier?

Post by **HenryJ** » Tue Oct 31, 2006 2:21 pm

Yes. They have a coil that when warmed expands to turn the valve in the center regulating the fluid that provides resistance for the fan to hub connection.

This coil is permanently attached at both ends. Modification to the coil itself could lead to its failure.
I would say that modification of its operating range would be very difficult and somewhat risky.
It would take lots of trial and error, and I am not sure any changes would be easily repeatable.

Stretching the coil might be a possibility, but how would you get the temperature range correct?
Not something that I am going to try.

crew cab sonoma · Post by **crew cab sonoma** » Wed Nov 01, 2006 11:00 am

HJ, i have some doubts about that wear vs. temp scale`s accuracy... perhaps it was based on old engines, and/or lubricant technology, but i have seen plenty of cylinders on newer engines that have almost no cylinder wear, even after 15+ years and 120K+ miles...

no ridge at the top, no taper, and the honing pattern is still fully visible throughout the cylinder...

now presuming at least two cold starts a day, that 10-15 years is more than enough run time at say, under 100 deg. F coolant temps, to exceed 50 HRS. total.... but still no wear anywhere near what that graph indicates...

of course, there are engines that will have plenty of cyl. wear in that time, but many more that simply dont...

that graph is probably off by a factor of 10, or more, on the wear #`s for modern engines and lubricants, but i would say the overall curve is still fairly correct...

quickbiker · Post by **quickbiker** » Fri Nov 10, 2006 9:55 am

Looks like a draw. Interesting...

killian96ss · Post by **killian96ss** » Fri Nov 10, 2006 10:54 am

quickbiker wrote:Looks like a draw. Interesting...

The poll may say 50/50, but this is only based on 8 votes, so I think you need more votes for it to mean anything, and I also noticed that even though the poll is even most of the comments seem to favor the electric fans.

I personally like electric fans since they allow for quicker warm ups, reduced engine drag = (more hp to use) and better gas mileage, better low speed cooling, longer water pump life, no chance of your fan chopping up your radiator, and if you run a dual fan set up you always have the second fan as back up in case your primary fan fails.

As you already know when a clutch fan fails you are stuck, period.

In order for an electric fan set up to be reliable you must have a good charging system as has Brule has already pointed out, and you need to use relays and keep extras with you just in case one fails. Some people will say that electric fans are only adequate at idle or slow speeds, but they really don't know what there talking about since airflow at higher speeds will more than compensate for a slightly slower fan speed or CFM rating.

I have dual fans on my SS and find it impossible to come anywhere near overheating the engine even during high speed track driving which is way more abusive that daily driving, rock crawling, or towing.

Steve

quickbiker · Post by **quickbiker** » Fri Nov 10, 2006 8:54 pm

Yes, but the key is "reliability". Not good points or bad points.

2kwik4u · Post by **2kwik4u** » Sat Nov 11, 2006 5:20 am

quickbiker wrote:Yes, but the key is "reliability". Not good points or bad points.

Not sure if you are saying E-fans are good or bad here.

My $.02.......E-Fans all the way. After having two clutch fans fail on my '00 Xtreme, One of which spun off the front of the motor and tore up ~$2,500 in parts, I'll never go back to a clutch fan. I've also had low speed cooling problems on my BONE STOCK '04 ZR5 which I can only think will be cured next summer with a nice electric fan setup.

I personally don't see it as a question of which to use, but a matter of timing on how fast you can make the switch.

Your Milage may vary, no warranties neither expressed nor implied.

20Blazer00 · Post by **20Blazer00** » Sat Nov 11, 2006 3:51 pm

Well I think that the factory has answered that question. The new '07 base engine (4.3L) silverados/yukons/etc all come with electric fans.

But the E-fan has to be the answer if the factory finally sees the benefits of them then why argue here...Get er done - switch.

F9K9 · Post by **F9K9** » Sat Nov 11, 2006 6:59 pm

Or we can wait to see if there will be an '08 truck!

snowsurfer · Post by **snowsurfer** » Mon Nov 13, 2006 9:58 am

I don't off road nor do I race but my experience with E fans are that they cool the eng temp real good and probably a tiny bit gained on performance. The only objection I had was it didn't seem to cool my AC as good. Again maybe it's just my application and no heavy duty off roading or anything but as a daily driver the clucth fan provided much more cooling air to the ac for me so I took it off and went back to the clutch fan.

2kwik4u · Post by **2kwik4u** » Mon Nov 13, 2006 10:24 am

For an idea of the amount of power gained......Jeremy dropped from a 12.15@110 to an 11.94@111 by removing the stock fan, and running no fan down the strip.

~20hp or so is what the figures came out to be.

killian96ss · Post by **killian96ss** » Mon Nov 13, 2006 1:05 pm

2kwik4u wrote:For an idea of the amount of power gained......Jeremy dropped from a 12.15@110 to an 11.94@111 by removing the stock fan, and running no fan down the strip.

~20hp or so is what the figures came out to be.

If the track conditions (track temp, air temp, humidity, etc) were the same and there was no wheel spin on either run then I would have to say that 20hp is a pretty good gain.

As we all know there are a lot of variables in drag racing that can change the 1/4 mile times even on the most consistent vehicles.

Steve

2kwik4u · Post by **2kwik4u** » Tue Nov 14, 2006 4:00 am

AWD with 4 drag radials = No Spin.......Weather between the two runs was within 5% or so temp and humidity wise. Same track one spring run, one winter run. Nothing really changed between the two other than the fan.

crew cab sonoma · Post by **crew cab sonoma** » Wed Nov 15, 2006 5:54 am

"within 5%" on temperature is open to interpetation.... depends on the range of your scale.

now if you meant within 5 degrees...

dont forget atomsphereic pressure, as well....

i usually run these 3 factors, plus my track elevation, through a special calulator, to obtain a DENSITY ALTITUDE figure.
i then write these figures onto the back of my timeslips, so i can compare them on different dates.

2kwik4u · Post by **2kwik4u** » Wed Nov 15, 2006 7:31 am

44 degrees one day, and 40 degrees the other day = 10% difference in temperature.

Not sure on the density altitude, however I'd say it was dayum close, as it was the same track, and temp and humidity were dayum close.