Horsepower Requirements for fan?

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Sharecropper

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I'm finishing up my P400-700R4-NP241 build to go into my M1028 and am considering replacing the fan & clutch with a separate thermostatically-operated radiator-mounted fan in order to save a couple horsepower during higher operating temperatures. Just wondering if anybody has ever calculated the horsepower requirements of the fan when fully engaged. I know it does rob horsepower, because you can feel it when the fan comes on in hot weather.

While we are on this subject, what would be the ideal thermostatically-operated fan to purchase?

Thanks in advance for comments.
 

chevymike

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I recently moved from a mechanical fan to an electric fan setup in my '48 Chevy Sedan as I needed better cooling at idle and low speeds (think stop and go traffic). I did a ton of research on fans and controllers. There are a lot of fan options out there but for my space and needs, I used a Flex-a-Lite Black Magic Extreme fan. 3000cfm and being a S blade design, it is very quiet.

Now more important than which fan you use (which you will need to find a setup to pull max airflow across the full radiator) is the controller. Simple temp switch/probe styles are not a great solution as they basically toggle the fan on or off at preset temps. This tends to cause temp swings as it cycles between these values. Also these have a huge current surge when then turn on because they are trying to spin it up to full speed immediately. This is hard on the electrical system.

After doing a lot of research on fan controllers (not temp switch type), there are a number of ones out there. Many are setup as variable speed controllers that will ramp up the fan speed as the temp increases. These are great as they spin the fan at the speed needed to hold a temp. Unfortunately many of them are low quality and do not have the long term reliability. I found two that have a great reputation in the hot rod world and have had very long term reliability. Of those two, I picked this company because they offered a screw in type temp sensor, where the other one was a probe you push into the radiator fins, which I will not do.

Check out https://www.autocoolguy.com/ for different models of controllers. They offer ones from 50amps max fan draw up to 200amps max. They come with "soft start" which does not load up the electrical system when it turns on and will ramp up to max speed as needed. It varies the speed to keep your preset (which is adjustable) temp. It also comes with an A/C trigger which will turn on to a minimum fan speed (you can adjust) and an override switch which will turn to max speed. I love it as I have it set in my '48 Chevy to 180* and regardless of outside temp, A/C on or off or whatever traffic I might be in, it has never gone over my set temp.

Hope this is helpful.
 

Sharecropper

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I recently moved from a mechanical fan to an electric fan setup in my '48 Chevy Sedan as I needed better cooling at idle and low speeds (think stop and go traffic). I did a ton of research on fans and controllers. There are a lot of fan options out there but for my space and needs, I used a Flex-a-Lite Black Magic Extreme fan. 3000cfm and being a S blade design, it is very quiet.

Now more important than which fan you use (which you will need to find a setup to pull max airflow across the full radiator) is the controller. Simple temp switch/probe styles are not a great solution as they basically toggle the fan on or off at preset temps. This tends to cause temp swings as it cycles between these values. Also these have a huge current surge when then turn on because they are trying to spin it up to full speed immediately. This is hard on the electrical system.

After doing a lot of research on fan controllers (not temp switch type), there are a number of ones out there. Many are setup as variable speed controllers that will ramp up the fan speed as the temp increases. These are great as they spin the fan at the speed needed to hold a temp. Unfortunately many of them are low quality and do not have the long term reliability. I found two that have a great reputation in the hot rod world and have had very long term reliability. Of those two, I picked this company because they offered a screw in type temp sensor, where the other one was a probe you push into the radiator fins, which I will not do.

Check out https://www.autocoolguy.com/ for different models of controllers. They offer ones from 50amps max fan draw up to 200amps max. They come with "soft start" which does not load up the electrical system when it turns on and will ramp up to max speed as needed. It varies the speed to keep your preset (which is adjustable) temp. It also comes with an A/C trigger which will turn on to a minimum fan speed (you can adjust) and an override switch which will turn to max speed. I love it as I have it set in my '48 Chevy to 180* and regardless of outside temp, A/C on or off or whatever traffic I might be in, it has never gone over my set temp.

Hope this is helpful.
Outstanding reply. Thanks so very much.
 

Sharecropper

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Ok I have made the decision to remove my brand new Derale fan and clutch and go with an electric fan instead. I’ve watched several videos including this very informative one at
I have concluded that I want a pull-through with straight blades, however I would prefer a 24-volt but cannot find any brand which offers it. I may explore around with a HMMWV fan to see if I can re-engineer something like I always am doing. Whatever I do, I will post it in my rebuild thread for all to see.
 

chevymike

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Having been in the hot rod world for almost 4 decades, straight blade fans are VERY noisy. You and everyone around you will know when it is running. Personally, I would look at S blade fans. Most OEM fans have gone this way because of noise issues.

If you want a very high CFM fan, you might look at a mid 90's Ford Tauras two speed fan. I think on high it's around 4900 cfm.
 

Rutjes

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Interested to see what you come up with. I'm looking into improving the cooling of the 6.5 TD on my K1500. Most, if not all will be copied onto the 6.5 I have for my CUCV. Anyway, I came up with a high flow waterpump, 21" fan, severe duty fan clutch, Champion radiator and the Paradox cooling kit. It'll be interesting to see what you come up with to reduce parasitic loss of HP due to the fan assembly while maintaining max cooling though.

Couple days ago, I read about a guy who had a new adapter made for the mechanical fan to remove the clutch. Improved his cooling performance as the fan is always fully engaged (Might lead to some over cooling on cold days though?). But it does lower the parasitic loss of HP due to it's lower weight. Might be something to consider? Can't find the thread, but when I do I'll post it here.
 

Sharecropper

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Interested to see what you come up with. I'm looking into improving the cooling of the 6.5 TD on my K1500. Most, if not all will be copied onto the 6.5 I have for my CUCV. Anyway, I came up with a high flow waterpump, 21" fan, severe duty fan clutch, Champion radiator and the Paradox cooling kit. It'll be interesting to see what you come up with to reduce parasitic loss of HP due to the fan assembly while maintaining max cooling though.

Couple days ago, I read about a guy who had a new adapter made for the mechanical fan to remove the clutch. Improved his cooling performance as the fan is always fully engaged (Might lead to some over cooling on cold days though?). But it does lower the parasitic loss of HP due to it's lower weight. Might be something to consider? Can't find the thread, but when I do I'll post it here.
Yeah I have that same setup that Leroy is offering, however I purchased my FlowKooler water pump directly from FlowKooler and my high-volume fan directly from Derale. My new clutch is NOS GM.

After I thought about it and realized that the OEM fan and clutch robs horsepower, it was a no-brainer to make the transition to an electric fan. I am in the process now of exploring all the options and availability to determine how to configure the system. If possible I want to use 24-volt so the fan will be powered from the rear battery. So far I haven’t found any 24-volt fans from the regular suppliers. I may take a look at modifying a HMMWV 24-volt fan to see if I can make that work. I’ve been known to do some pretty crazy things, so this sort of thing is nothing new for me.
 

chevymike

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I believe I have found the fan. Flex-A-Lite Model 104812 is a 24-volt which moves 3,300 cfm and has an electronic controller. I will continue looking to see if I find ay other 24-volt possibilities.

I have the 12v version but without the built in controller. In my research, lots of people having failures of the built in one, typically within 6 months. Why I opted to go the route I did. The fan itself works really well and is quiet. Just wouldn't trust the built in controller.
 

Sharecropper

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I have the 12v version but without the built in controller. In my research, lots of people having failures of the built in one, typically within 6 months. Why I opted to go the route I did. The fan itself works really well and is quiet. Just wouldn't trust the built in controller.
Yes that is my thinking also,to forego the built in controller in favor of a probe switch in my HMMWV crossover.
 

MarcusOReallyus

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After I thought about it and realized that the OEM fan and clutch robs horsepower, it was a no-brainer to make the transition to an electric fan.
The electric fan ALSO robs power. Where do you think the energy to move that air is coming from? It ain't free! An electric fan puts a load on the alternator, which is driven by the engine.

"Oh, but the engine is already spinning the alternator, so it doesn't take any extra power to run the electric fan. It IS free!"

Nope. It doesn't work that way. The extra load creates extra resistance in the windings, which translates very directly into load on the engine. Horsepower.
TINSTAFFL. Or, in technical terms, the 2nd Law of Thermodynamics, and you WILL obey the 2nd Law of Thermodynamics. There is no lawlessness in the realm of physics.

Energy is required to move air, and that energy has to come from somewhere. Whether mechanical or electric fan that energy is all coming from the same place - the engine. Ultimately, from the fuel you are burning. (Which got it from the sun, back a few years.)

Now, it is possible that the electric fan is using that fuel more efficiently, leaving more engine power for other things (like moving your vehicle). And with a smart controller that varies the fan speed, this is almost certainly true. But without the controller? Well, maybe. Maybe not. Depends on a lot of things.

The point is, you can't simply assume that an electric fan will rob less power from the engine. It WILL rob power. How much is a the question.
 

Sharecropper

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The electric fan ALSO robs power. Where do you think the energy to move that air is coming from? It ain't free! An electric fan puts a load on the alternator, which is driven by the engine.

"Oh, but the engine is already spinning the alternator, so it doesn't take any extra power to run the electric fan. It IS free!"

Nope. It doesn't work that way. The extra load creates extra resistance in the windings, which translates very directly into load on the engine. Horsepower.
TINSTAFFL. Or, in technical terms, the 2nd Law of Thermodynamics, and you WILL obey the 2nd Law of Thermodynamics. There is no lawlessness in the realm of physics.

Energy is required to move air, and that energy has to come from somewhere. Whether mechanical or electric fan that energy is all coming from the same place - the engine. Ultimately, from the fuel you are burning. (Which got it from the sun, back a few years.)

Now, it is possible that the electric fan is using that fuel more efficiently, leaving more engine power for other things (like moving your vehicle). And with a smart controller that varies the fan speed, this is almost certainly true. But without the controller? Well, maybe. Maybe not. Depends on a lot of things.

The point is, you can't simply assume that an electric fan will rob less power from the engine. It WILL rob power. How much is a the question.
Marcus - thanks for your reply. I was kinda waiting for you to chime in.

Everything you stated in your post is true. And while I appreciate and agree with your message, I am a little disappointed in your method of delivery, which came across as somewhat arrogant. Regardless, I will respectfully offer my response, which I hope will be interpreted by yourself and other readers as a further justification of replacing the engine-driven fan and clutch with a thermostatically-controlled electric fan.

My goal in this regard is to relocate the energy source for supplemental cooling away from direct engine-driven, to a "softer", longer-term energy replenishment process provided through the passenger-side altenator. As everyone knows (or should know), the OEM design is for the clutch to engage the fan at an elevated operating temeperature to pull additional cooling air through the radiator to increase the heat sink action of the radiator fins. This is especially helpful in hot weather when sitting in traffic, when very little air is being forced through the radiator via ground speed and slower engine speeds cause a reduced flow rate of coolant through the radiator. During these slow-traffic times, the loss of horsepower to engage the clutch and fan is acceptable and the resulting horsepower loss rarely missed. However it is the long hot summer drives up inclines and/or pulling a load which makes the loss of horsepower extremely inconvenient and annoying. In these situations, the horsepower capture of the clutch engaging is instant and dramatic, which could not come at a worse time when more horsepower is needed to crest the hill. So by relocating the energy source for supplemental cooling to the electrical system, the energy requirements and replenishment can be spread out over time instead of robbing horsepower on-demand from the engine.

And as you stated, the alternator must furnish the electrical energy used by the electric fan. No argument there. However the electrical energy for an electric fan is not furnished directly and immediately from the alternator, but instead, is obtained from electrical storage, i.e. the battery. The alternator only generates electricity to replenish electricity removed from a battery. The load on an alternator is directly related to the amount of electricity it must replace in a battery. The higher the loss of electricity in a battery, the higher the load on the alternator (up to the maximum of the device). The electrical load to run an electric fan for a few seconds in traffic or a few minutes up a long hot incline will not drain a strong battery to the point of demanding a maximum draw from the alternator. The 24-volt Flex-A-Lite fan identified in a previous post only draws 11 amps. This electric fan would need to run more than a few minutes to deplete a strong battery to a point of requiring a maximum recharging from the alternator.

Think about this - instead of the single rear battery, what if you had 50 strong batteries wired in Parallel in the bed of the truck, from which the power requirements for an electric fan were obtained. The percentage "withdrawal" of electricity for a couple minutes of fan operation would hardly be noticable to the alternator. This is what I am talking about, to "spread-out" the power requirements over a period of time and relocate the power source from the on-demand engine-driven fan.

I hope I have been able to clarify my theory for you.
 
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Curtisje

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I like the information coming out of this discussion.

I run two 1100CCA batteries in my CUCV with the stock electrical system. Everytime I start the truck I get alternator belt squeal during the cycling of the glow plug system as it draws about 120+ amps. I have run the truck with 4 1100CCA batteries and still experience the same alternator belt squeal. 120 amps is quite a bit more than your 10 amps for your electric fan but my only point is that regardless the amount of battery power available the alternator will have to replace the same amount and work as hard as is needed to do it.

I also run 2 electric fans on the front of my radiator in addition to the mechanical fan and clutch on the water pump pulley. I do that because I spend a lot if time traveling at less than 20 mph in the high desert at temperatures of 110+. I have a switch fastened to the outside of the radiator where the coolant enters. It works quite well.

Just my experiences above to share with you guys. I hope to see exactly what you go with. Good luck.
 

MarcusOReallyus

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Marcus - thanks for your reply. I was kinda waiting for you to chime in.

Everything you stated in your post is true. And while I appreciate and agree with your message, I am a little disappointed in your method of delivery, which came across as somewhat arrogant.
I'm sorry it came across that way. That was not my intent.


Regardless, I will respectfully offer my response, which I hope will be interpreted by yourself and other readers as a further justification of replacing the engine-driven fan and clutch with a thermostatically-controlled electric fan.
I didn't say it was NOT a good idea. My point was responding to what you said. I didn't have any other information. You said simply that you were replacing it because you found out that the mechanical fan robs horsepower from the engine. I was simply pointing out that any fan requires energy from the engine. (Unless you are running a solar array on the roof, or a gas generator in the bed. :D)


There are tons of people out there who think that the alternator provides free energy. Just look up any forum or YouTube video on running an engine on hydrogen gas generated by that engine's alternator. It's often very hard to convince them that the alternator puts a load on the engine which has to be paid for in fuel. (Well, okay, it's often impossible to convince them since the only reason we aren't all running on free hydrogen is because the oil companies keep killing the inventors. The 2nd Law of Thermodynamic doesn't apply when oil companies are killing inventors, you know. :( ) Hence my comment about, "Hey, it's already spinning!" That is a very common response from those folks.



I hope I have been able to clarify my theory for you.
Sounds reasonable. Might work. As with any idea that seems good, the proof will be in the pudding, but I think it's well-thought out. I'm sure a lot of folks will be interested in hearing the results over time.

Thank you for spelling it out! (y)

What are you doing about shrouding the fans? Got pics?
 

Sharecropper

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I'm sorry it came across that way. That was not my intent.




I didn't say it was NOT a good idea. My point was responding to what you said. I didn't have any other information. You said simply that you were replacing it because you found out that the mechanical fan robs horsepower from the engine. I was simply pointing out that any fan requires energy from the engine. (Unless you are running a solar array on the roof, or a gas generator in the bed. :D)

There are tons of people out there who think that the alternator provides free energy. Just look up any forum or YouTube video on running an engine on hydrogen gas generated by that engine's alternator. It's often very hard to convince them that the alternator puts a load on the engine which has to be paid for in fuel. (Well, okay, it's often impossible to convince them since the only reason we aren't all running on free hydrogen is because the oil companies keep killing the inventors. The 2nd Law of Thermodynamic doesn't apply when oil companies are killing inventors, you know. :( ) Hence my comment about, "Hey, it's already spinning!" That is a very common response from those folks.





Sounds reasonable. Might work. As with any idea that seems good, the proof will be in the pudding, but I think it's well-thought out. I'm sure a lot of folks will be interested in hearing the results over time.

Thank you for spelling it out! (y)

What are you doing about shrouding the fans? Got pics?
Marcus - no problem. No offense. Yeah I agree with you, there are guys out there that will buy into anything they read on some of they other forums. I am a member on a couple and you wouldn’t believe some of the stupid preppy questions I get. I used to try to respond but got tired of all the arguments so now I just stay off them. Steel Soldiers is the only site I visit regularly.
That Flex-A-Lite #104812 I have tentatively chosen is a 24-volt which pulls 11 amps. If it was a 12-volt it would pull 22 amps. At 11 amps the fan can run all day long without dipping into a good battery’s reserve. The #104812 fan pulls 3,300 CFM and has its own shroud. Unless I find a better one, that is the fan I will buy.
The reason I will forego the electronic controller is because it is, well, electronic. My goal on this truck build is to eliminate as many electronic devises as possible. Mechanical injection pump, all mechanical gauges ( oil pressure, water temperature, fuel pressure, oil temperature, transmission temperature ) and dumb 700R4 transmission. I’m even staying with the OEM fuel lift pump because it is dumb. Bout the only thing electronic is the glow plug controller and I am installing a push button override just in case “it” hits the fan (pardon the pun). Small relays can be carried along and fixed in the bush, but large mission-dependent components which rely on electronics to get me home are being eliminated if possible. One example of this would be the electronic controller for a 4L80E transmission. That is why my P400 has a dumb 700R4 behind it. Rated at 450 horsepower, by the way.
Batteries. Let’s talk batteries. When I begin to reinstall the front clip after my engine/tranny/TC has been installed, I plan on designing, fabricating, and installing A new, stronger and larger rear battery tray to support at least 2 and maybe 3 batteries to supply mega 24-volt amperage capacity. This new tray will be supported from the frame instead of the inner fender. All aftermarket accessories will be 24-volt and powered from this battery bank. Inverter, fridge, ham radio, etc will all be 24-volt wired through a BlueSea panel. The front battery will remain 12-volt and configured as OEM and charged from the driver’s side alternator as originally designed.
Hope this helps to explain things. Have you subscribed to my rebuild thread?
 

Sharecropper

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I like the information coming out of this discussion.

I run two 1100CCA batteries in my CUCV with the stock electrical system. Everytime I start the truck I get alternator belt squeal during the cycling of the glow plug system as it draws about 120+ amps. I have run the truck with 4 1100CCA batteries and still experience the same alternator belt squeal. 120 amps is quite a bit more than your 10 amps for your electric fan but my only point is that regardless the amount of battery power available the alternator will have to replace the same amount and work as hard as is needed to do it.

I also run 2 electric fans on the front of my radiator in addition to the mechanical fan and clutch on the water pump pulley. I do that because I spend a lot if time traveling at less than 20 mph in the high desert at temperatures of 110+. I have a switch fastened to the outside of the radiator where the coolant enters. It works quite well.

Just my experiences above to share with you guys. I hope to see exactly what you go with. Good luck.
Hey Curt - I am of the strong opinion that your squealing belts are caused by a misalignment of the alternator pulleys to the water pump pulley. You can usually sight the belt to see if there is a slight bend in it as it crosses over the pulleys. Take a look at this with a good light and let us know what you see.
 

Curtisje

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Hey Curt - I am of the strong opinion that your squealing belts are caused by a misalignment of the alternator pulleys to the water pump pulley. You can usually sight the belt to see if there is a slight bend in it as it crosses over the pulleys. Take a look at this with a good light and let us know what you see.
Thanks for the recommendation. I'll look at that once I get the rear end put back together. I'm not real concerned as it only squeals twice in the morning. I just let it idle until the sequence is complete and then I drive off. I want to put more time or money into it than I have to right now. I'm trying to paint the frame of my 7th Marines M1008 and get it back together so I can tear this down and rebuild it as well.

I will take a minute and look at that though. Thank you.


Edit: I looked it over. They seem to be lined up correctly. The driver side belt looks like it my be a little loose. I'll tighten it up and keep on trucking. Thanks for the advice though
 
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shotty

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I put dual electric fans on my truck, you could do the same and wire them in series for 24 volts. The reason I did this was so incoukd ensure all tubes in the radiator had a fan pulling air across them. Our radiators are quire tall so instead of one huge fan I got two smaller ones. They work great and should one fail I still have another one to get me home with.
 
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