kissfans03ss Posted August 12, 2011 Report Share Posted August 12, 2011 I was always taught that when the oil or fluid in a clutch style fan reaches temperature it locks up and provides cooling for the motor. I have heard of tests on TV/magazines saying that a clutch style fan works better than a flex a lite fan. For my money I would go with the electric fan set up, you have no control over clutch style fans but electric fans have alot more options like stated before. Sent from my Droid using Tapatalk Quote Link to comment Share on other sites More sharing options...
matt 2k12 Posted August 12, 2011 Report Share Posted August 12, 2011 I have to ask were you are getting this logic. The e fans provide more cfm of cooling then a clutch fan and are at a constant cfm level( or programmable level), not an rpm based level. I can also tune my fans to come on at what ever temp i so choose and go off at what ever temp i choose, not based on the air temp that is blowing past or around the clutch fan. I can also program my fan or fans to come on with a certain ac pressure as a fail safe. I can also have my fans stay on when the truck is shut off if the temp is above a settable point, and set a time limit for which they stay on, and in addition i can also add a manual switch and leave the fans on(and is some cases an electric water pump) to cool the motor while its not running, of coarse not available with a clutch fan. And on top of it all, the e fans only put a slight load on the alternator where as the clutch fan can put much more load on the motor sucking more hp out of it, to the point where a lot of the old school hot rods run a electric motor on the water pump/fan so its not crank driven and adds the ability of the cooling when the motor is off. Yes yes yes, you can customize and "tune" your e fans and all that. I'm not arguing that, ok? And I am not saying that on this specific truck belt driven fans are always better, ok? I was making a general statement regarding e fans vs combustion powered fans. Its simple really. There is a reason we are not driving electric trucks. Similarly, there is a reason all the electric cars on the market today suck ass. The power from combustion is far greater than anything your battery can possibly muster. It is a simple fact on this application: Combustion Power > Electrical Power. The funniest thing to me is that on these trucks with such a big engine bay all you need to be doing is be driving down the street at a constant speed and the motor basically cools itself. Stop and go traffic, that is a different story. I would be interested to see this CFM chart you have comparing the e fans to the OEM setup, and I would like to know at what conditions the numbers were reached and if it included the air turbulence from a vehicle in motion at X mph as a baseline. Lastly, a true cooling upgrade for this truck would be a purpose built racing radiator and upgraded / aftermarket clutch fan assembly. Quote Link to comment Share on other sites More sharing options...
shadowsniper3006 Posted August 12, 2011 Report Share Posted August 12, 2011 (edited) I did a bunch of reading on this today after reading your post and from what i can see, i was wrong. I made a bad assumption and the clutch fan will pull more cfm of air. From the looks of it, the clutch fan can pull around 10,000 cfm at higher rpms where as the fan kit i use pulls 7000 cfm. However, from what i saw, the e fan will move more air at an idle then the clutch fan will(but this looks like its for our fan size only which makes it specific to our trucks not as a general statement), which as you stated is the time when you need the cooling not at the higher rpm levels because you have the wind moving through at vehicle speed. So as a general statement your right. However, based on the ability to tune the fans to come on when i want them, possibly more air movement at idle, being able to leave them on when the truck is shut off, and not having the drag on the motor, i would still take them over the clutch fan. for those that had the same impression, here is a short but good read http://www.thetruckstop.us/forum/showthread.php?24074-Anyone-know-how-many-cfm-the-fan-pulls Edited August 12, 2011 by shadowsniper3006 (see edit history) Quote Link to comment Share on other sites More sharing options...
matt 2k12 Posted August 12, 2011 Report Share Posted August 12, 2011 Good read. Like I said, do both. Put E fans in front and mech fans in back and you are covered at low speed / idle and highway speeds. Well its Friday. Quote Link to comment Share on other sites More sharing options...
chpspecial Posted August 12, 2011 Report Share Posted August 12, 2011 Good read. Like I said, do both. Put E fans in front and mech fans in back and you are covered at low speed / idle and highway speeds. Well its Friday. pusher fans don't really work, as fans loose 30-40% efficiency when they become pushers. the best way to cool is to use a puller fan, and the stock clutch fan will exceed any "helper" pusher fan. Second, they will block air flow negating thier use. If you notice the only time that GM has used pushers are on auxillary coolers and because space limits where reached. Quote Link to comment Share on other sites More sharing options...
matt 2k12 Posted August 13, 2011 Report Share Posted August 13, 2011 I'm honestly not an advocate of e fans if you didn't already know. If you must have them put them in front, behind, somewhere, as a supplement, not a replacement. Or better yet put them on your tranny and motor oil coolers. Quote Link to comment Share on other sites More sharing options...
Cramer Posted August 13, 2011 Report Share Posted August 13, 2011 Ok I just dont see the common sense of all this. My clutch fans at idle in traffic kept my ect at 195-205*. My efans keep my ect at 190* max. With a/c on in 100* temps in traffic after driving 45 min. I gained almost 2mpg and better response. This was after a cam swap too. The clutch fan flows more air at upper rpm's yeah but my fans are tuned off at 35mph unless ect is over 180* and or a/c presssure is at the setpoint. There is no extra drain or load on the motor and when the fans turn on when the limit is met, the engine cools down in less than a min. Quote Link to comment Share on other sites More sharing options...
shadowsniper3006 Posted August 13, 2011 Report Share Posted August 13, 2011 (edited) Ok I just don't see the common sense of all this. My clutch fans at idle in traffic kept my ect at 195-205*. My efans keep my ect at 190* max. With a/c on in 100* temps in traffic after driving 45 min. I gained almost 2mpg and better response. This was after a cam swap too. The clutch fan flows more air at upper rpm's yeah but my fans are tuned off at 35mph unless ect is over 180* and or a/c pressure is at the set point. There is no extra drain or load on the motor and when the fans turn on when the limit is met, the engine cools down in less than a min. i agree, the e fans are a better choice and IMO i would much rather have them, even if its just based on the slight amount of hp gained. However, to answer your question(at least from what i just read), the efans will move more air at idle therefor keeping the truck cooler at idle(just what you saw). And when the AC is on the fans will always be on, i assume the clutch fan will still operate on temp only not based on ac pressure or just the ac being on. It would seem the only benefit of the clutch fan would be if your coolant temp starts to climb while your moving at a higher rpm, maybe as your going down the track at WOT and your coolant temp rises, however i just checked my logs from Wednesday and going down the track with the thermostat open i only gained 6 degrees, with the thermostat closed i only gained 10 degrees, and this is with the fans off...so I'm not sure where the clutch fan would do our trucks any good. In a general statement, the clutch fan can flow more cfm of air, it just might not do it where our trucks need it. But from what it says in that link, this may only be limited to our application. The duramax uses a larger diameter fan with a different blade angle and flows much more cfm in the lower or idle rpms. Its possible this larger fan with a different design can flow more cfm at idle then any e fan kit can so it then becomes the better choice for cooling based only on coolant temps and not performance gains. But if an e fan kit can't keep the truck cool the performance of not having a crank driven fan may be over taken by the heat soak caused on the motor which is running at a higher temp. Does that make any sense? Edited August 13, 2011 by shadowsniper3006 (see edit history) Quote Link to comment Share on other sites More sharing options...
matt 2k12 Posted August 13, 2011 Report Share Posted August 13, 2011 (edited) i agree, the e fans are a better choice and IMO i would much rather have them, even if its just based on the slight amount of hp gained. However, to answer your question(at least from what i just read), the efans will move more air at idle therefor keeping the truck cooler at idle(just what you saw). And when the AC is on the fans will always be on, i assume the clutch fan will still operate on temp only not based on ac pressure or just the ac being on. It would seem the only benefit of the clutch fan would be if your coolant temp starts to climb while your moving at a higher rpm, maybe as your going down the track at WOT and your coolant temp rises, however i just checked my logs from Wednesday and going down the track with the thermostat open i only gained 6 degrees, with the thermostat closed i only gained 10 degrees, and this is with the fans off...so I'm not sure where the clutch fan would do our trucks any good. In a general statement, the clutch fan can flow more cfm of air, it just might not do it where our trucks need it. But from what it says in that link, this may only be limited to our application. The duramax uses a larger diameter fan with a different blade angle and flows much more cfm in the lower or idle rpms. Its possible this larger fan with a different design can flow more cfm at idle then any e fan kit can so it then becomes the better choice for cooling based only on coolant temps and not performance gains. But if an e fan kit can't keep the truck cool the performance of not having a crank driven fan may be over taken by the heat soak caused on the motor which is running at a higher temp. Does that make any sense? It made sense until the last few sentences or something. Sounds to me like the only benefits are idle and stop and go traffic, which I try to avoid. We are maybe in different areas. Not a lot of congestion and traffic jams here. You really telling me you want those wimpy e-fans when you are going 4 or 5 seconds (only 4 gears my friend) at WOT down the track or hauling a boat uphill when you could have a clutch fan matching those RPM in speed and intensity? I dont know though, my enthusiasm is in GT/road course/street style drivng so coolant temps over a long duration are more of a concern than oveheating @ WOT for 11 or 12 seconds. Which goes back to the e fans for idle and low speed. Does that make any sense? And yall are worried about what, 1 or 2 hp? Have there been any dynos showing the gains from e fans? max 7 hp or something? Put a 25 or 50 shot on your truck if you are worried about hp on a dyno or at the strip. Im telling you the best is a purpose built aluminum racing radiator, lower thermostat, and if someone makes an aftermarket fan / clutch assembly, billet and all that shit. The pitch of the vanes, the fan material, you can go all out. I would think someone makes a badass clutch fan assembly for this truck or similar GM applications for aftermarket / racing purposes. I'm sure its all readily available, I'm just new to these trucks. To me, losing that few meaningless RPM HP on an e fan is worth the long term longevity of my engine in those crazy days under this hot and dry west Texas sun. To me its more efficient and costs less. With stock fan my needle is never past the middle, whatever temp that is. Its always a few marks lower temp. Edited August 13, 2011 by matt 2k12 (see edit history) Quote Link to comment Share on other sites More sharing options...
misterp Posted August 13, 2011 Report Share Posted August 13, 2011 (edited) The reason GM put efans on the 2005+ light trucks was to gain 0.15-mpg to meet tightened Congressional EPA/CAFE mandates. The mechanical fan does pull the most airflow (6000-7000 CFM) but the engine must be turning 1800+ RPM to do so; at idle the EFans (on high speed) will pull far more airflow than the mechanical fan at engine idle. Reasons to use EFans: 1. Fans are only ON when required (the clutch fan "runs" all the time) 2. At idle, engine and A/C get better improving through better airflow 3. Above 45-mph, the efans are turned off by the PCM (the clutch fan is a big air brake at freeway speeds) 4. In performance applications, 15-hp is freed from the motor and I personally felt this difference between 2500-3500 RPM 5. EFans will outlive the silicone clutch 6. EFans free lots of engine compartment room for other components (ducting, supercharging, turbos, etc) 7. EFans greatly ease engine maintenance, due to extra room freed underhood (essential for competition vehicles) Reasons to use mechanical Fan: 1. Mechanical fan is most efficient way to deliver maximum airflow at mid-range RPMs 2. If towing very heavy loads up steep grades at speeds at/under 45-MPH, the clutch fan will pull more airflow than efans 3. If towing very heavy loads at/under 30-MPH for any length of time, the efans will not be able to adequately cool the radiator The radiator is a good subject - the factory radiator is CRAP, it's barely big enough to keep up with cooling requirements in the summer, the tanks are plastic, and it's glued together. One of our fabricator friends took a GM truck radiator and pressurized it with an air compressor and it failed spectacularly at exactly 16-psi (tanks blew off). The Ford Lightning trucks have the exact same design/build quality issues. If you really want your truck to run cool it is necessary to upgrade your radiator to one that has a 2-row aluminum core. A lot of this is also subject to the prevailing outside conditions, my truck never breaks a sweat over 180 between October and March, but in the summer it runs about 195 with the 100-degree Texas heat and high humidity which tax the effectiveness of the radiator (it cannot shed as much heat to the atmosphere under those conditions). Mr. P. Edited August 13, 2011 by Mr. P. (see edit history) Quote Link to comment Share on other sites More sharing options...
kissfans03ss Posted August 13, 2011 Report Share Posted August 13, 2011 I love this mans explanations,I always learn something new when reading them. Sent from my Droid using Tapatalk Quote Link to comment Share on other sites More sharing options...
shadowsniper3006 Posted August 13, 2011 Report Share Posted August 13, 2011 (edited) It made sense until the last few sentences or something. Sounds to me like the only benefits are idle and stop and go traffic, which I try to avoid. We are maybe in different areas. Not a lot of congestion and traffic jams here. You really telling me you want those wimpy e-fans when you are going 4 or 5 seconds (only 4 gears my friend) at WOT down the track or hauling a boat uphill when you could have a clutch fan matching those RPM in speed and intensity? I dont know though, my enthusiasm is in GT/road course/street style drivng so coolant temps over a long duration are more of a concern than oveheating @ WOT for 11 or 12 seconds. Which goes back to the e fans for idle and low speed. Does that make any sense? And yall are worried about what, 1 or 2 hp? Have there been any dynos showing the gains from e fans? max 7 hp or something? Put a 25 or 50 shot on your truck if you are worried about hp on a dyno or at the strip. Im telling you the best is a purpose built aluminum racing radiator, lower thermostat, and if someone makes an aftermarket fan / clutch assembly, billet and all that shit. The pitch of the vanes, the fan material, you can go all out. I would think someone makes a badass clutch fan assembly for this truck or similar GM applications for aftermarket / racing purposes. I'm sure its all readily available, I'm just new to these trucks. To me, losing that few meaningless RPM HP on an e fan is worth the long term longevity of my engine in those crazy days under this hot and dry west Texas sun. To me its more efficient and costs less. With stock fan my needle is never past the middle, whatever temp that is. Its always a few marks lower temp. my truck sees almost all city driving and stop and go traffic. The highway is just a means to get to the next city driving experience, and when i do go to the track it takes me 45 minutes to get through an area that should take me 15 minutes. Yes i am telling you i want the wimpy e fans for the 12 second pass down the track, and if i tried to tow a boat up hill(or even down hill) my converter would try to evaporate the trans oil. i used my truck for stirring up trouble on the street and racing only. I would have to guess the 7 to 15 hp mark is about right for the gain of e fans over a clutch fan(however i changed this before i really started to dyno my truck so i can't tell you for sure). I would venture to say its all up in the higher rpms as well, which is were my truck lives. If it was 2 hp i would still do it, at this point i'm having to spend a 1000 plus dollars to maybe gain 15-20 hp. So i take what ever i can get to maintain a NA truck. I'm telling you, for the drag racing i do, I'll keep the clutch fan as a range target and keep the efans on my truck. Steve's post was very clear as to some of the reasons why but also like i said before, i can leave them and my water pump on if i was rushed for time between races. And i don't have any issues with cooling my motor in the area i live in. TX may be something else though. I hope we can just agree that we use our truck differently and what we do works best for what we do with the trucks Edited August 13, 2011 by shadowsniper3006 (see edit history) Quote Link to comment Share on other sites More sharing options...
matt 2k12 Posted August 13, 2011 Report Share Posted August 13, 2011 Sure, I agree. I think that is obvious. Plus I have a garage queen that is my "racecar" (w/clutch fan). Unfortunately I don't spend much time at racetracks. No 1/4 mile near me or road courses. I am street only but lots of highway and sub-urban roads. Both my vehicles are set up as street machines. Two radically different vehicles. Its a lotta fun, I love this truck. Nice change of pace from my Z. Quote Link to comment Share on other sites More sharing options...
dgrov3r Posted August 13, 2011 Author Report Share Posted August 13, 2011 That pretty much clears it up ...they are on the that ever so long list!! Quote Link to comment Share on other sites More sharing options...
matt 2k12 Posted August 16, 2011 Report Share Posted August 16, 2011 The main thing I got out of this thread is: UPGRADE THE RADIATOR ITSELF Quote Link to comment Share on other sites More sharing options...
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