Stock Radiator Fan CFM

zonker

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I realize that there is probably not any kind of answer.. but thought I would check just in case.

Any idea of the CFM for an 80 series cooling fan mounted to a modified blue hub and turning at say 2500rpm would create? Or any RPM for that matter if there is an answer looking at it that way?

I am just not sure that the dual SPAL fans attached to my Ron Davis radiator are doing a great job. Before I go to the cost and work changing back to "stock" setup.. I am hoping for some ideas that might spur my interest in doing so. Seen some temps this summer with A/C running and ambients of 95º that have me raising an eyebrow. Long fairly steep grade at 40mph (all she would do) over 8 to 9 miles in full sun.. engine temp of 219º at the top. I shut off the A/C at around 212º. May not be extreme.. but I sure don't like those numbers.. I expect something a little lower.. but maybe not realistic. Of course what probably makes it worse is staring at an Ultra Gauge as it inches upward. In typical fashion the stock gauge only bumped up a sliver!
 

LandLocked93

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Just have this to offer...
Matts Offroad and Recovery YT channel - He runs a Cherokee (the banana) to recover people in Moab. He's rebuilding it now and mentioned he was dumping his twin electrics (SPAL i think) for the stock fan as he learned it moved 4x the amount of air that the electrics did (with good shroud).
And the Jeep stock fan looks very similar to the 80's. Just looking at the SPAL and OEM side by side, the stocker appears a no-brainer.
Yeah there's science an' all involved, but I'd wager you'll be better off with the factory fan and whatever 'clutch juice' satisfies the environment criteria.
 
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The number thrown out was 15HP draw on the engine for the stock mechanical fan. I'm just parroting what I read somewhere.
It seems reasonable in all honesty.
Ever see a 15HP 12V electric motor? I'll give you a hint... It won't fit between the radiator and the engine. 12Klbs winches typically have 4-5HP motors, just to give you a size comparison.

So what size motors are on the electric fans? Hayden's 1500 CFM fan draws 17 amps at 12V = 204 watts or roughly .27HP. Seems laughably small, or the 15HP mechanical draw is Way to much.

Not sure, more research is need.
 
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I realize that there is probably not any kind of answer.. but thought I would check just in case.

Any idea of the CFM for an 80 series cooling fan mounted to a modified blue hub and turning at say 2500rpm would create? Or any RPM for that matter if there is an answer looking at it that way?

I am just not sure that the dual SPAL fans attached to my Ron Davis radiator are doing a great job. Before I go to the cost and work changing back to "stock" setup.. I am hoping for some ideas that might spur my interest in doing so. Seen some temps this summer with A/C running and ambients of 95º that have me raising an eyebrow. Long fairly steep grade at 40mph (all she would do) over 8 to 9 miles in full sun.. engine temp of 219º at the top. I shut off the A/C at around 212º. May not be extreme.. but I sure don't like those numbers.. I expect something a little lower.. but maybe not realistic. Of course what probably makes it worse is staring at an Ultra Gauge as it inches upward. In typical fashion the stock gauge only bumped up a sliver!
Maybe try expiramenting and installing a temporary cut off switch to shut off the fans at 35mph or so and faster when it's real hot out. See if that makes a difference. Having the fans on at speed can actually hinder cooling performance if I recall correctly.
 
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These are axial blade fans.

The static pressure in front of and behind the blades makes a HUGE difference in how much CFM they move, if any at all.

Think of your box fan in the house. If you lean the intake side against the wall, how much air does it move? Hardly any, because the static pressure to pull the air is too much, so the fan just sits there and freewheels, pulling hardly any HP.

However, sitting in the middle of the room with lots of room on all sides, the fan is moving tons of air, and the HP usage is at its peak.

So, a highly restrictive radiator will lessen the amount of air that will pull through because the static pressure is too high.

If you place pusher fans on the front and have your stock puller fan on the rear, you reduce the static pressure across the radiator, and make everything more efficient, UNLESS the air resistance across the radiator is too high because the fins are too close together and they cannot flow air well.

So many things involved on a specific system and how it was assembled. Small things can be huge mistakes, if you don't know how it all works together.

Do you still have your bottom cover plate on truck, below the radiator?

Do you have lights and a bumper in front of the grille?

Are your inner fender skirts in place between the inner fender and frame?

All the things listed above affect airflow and cooling.
 

zapatius

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I realize that there is probably not any kind of answer.. but thought I would check just in case.

Any idea of the CFM for an 80 series cooling fan mounted to a modified blue hub and turning at say 2500rpm would create? Or any RPM for that matter if there is an answer looking at it that way?

I am just not sure that the dual SPAL fans attached to my Ron Davis radiator are doing a great job. Before I go to the cost and work changing back to "stock" setup.. I am hoping for some ideas that might spur my interest in doing so. Seen some temps this summer with A/C running and ambients of 95º that have me raising an eyebrow. Long fairly steep grade at 40mph (all she would do) over 8 to 9 miles in full sun.. engine temp of 219º at the top. I shut off the A/C at around 212º. May not be extreme.. but I sure don't like those numbers.. I expect something a little lower.. but maybe not realistic. Of course what probably makes it worse is staring at an Ultra Gauge as it inches upward. In typical fashion the stock gauge only bumped up a sliver!

I don't know about CFM. My "worst" experience with a new stock blue fan clutch, a new Koyorad, new stock fan and new water pump - 106 degrees ambient in Moab, direct sun, stop and go traffic, A/C on high - I hit 212.

White Rim Trail - 102 degrees, A/C on 3 - constantly moving until camp, I never went over 197.
 

Broski

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Well I hope you get it figured out.
I was thinking of getting a RD rad, I would run the stock fan. But the numbers you speak of are what I’m trying to avoid.
Ultimately I would like it get it to run under 200 in all conditions with the AC on.
Excluding towing.
 

SmokingRocks

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I calc'd this like 4 or 5 years ago. Something around 5,800 CFM at 80% IIRC. I've seen 8 blade fans on some larger rigs that move 9,500 CFM Nothing beats the factory set up with a modified clutch.

For best cooling:
  • Radiator shroud needs to be in good condition and sealed around the edges
  • Fan clutch should be modified with 10,000 or 20,000 CST oil (I also run mine slightly advanced)
  • Belts need to be in good shape and tensioned correctly, at the higher RPM and load they can slip so I run my belts TIGHT
  • Run a leaner coolant mixture than 50/50, water has a much higher thermal capacity (ability to carry and transfer heat) than Glycol (coolant). I run a 70% Water / 30% Coolant + Water Weter (surface tension surfactant that prevents bubbles from forming, this improves the heat transfer efficiency)
    • If you do this you need to be cognizant of your coolants freezing point, and adjust it in the fall to stay below your winter temps
  • Gently hose your Radiator and fan clutch often to remove dirt, mud, dust
  • Make sure your radiator cap is good
On a trip last year to moab I was driving I-70 from Georgetown to the Eisenhower tunnel, this is a 7-8% grade for about 11 miles, starting at 8,500' and ending at over 11,000' above sea level. My rig was loaded out to about 7,000lbs, and it was an 85°F summer afternoon. From Georgetown to the tunnel I had the throttle pinned, not lifting once. I watched the temp (measured at the head and block discharge pipe) climb to 185°F, then the fan began to roar as the clutch engaged, over the next mile I watched the rig COOL ITSELF DOWN to 175°F while I was still holding the pedal to the floor. Pretty wild.

Now I don't have an AC Condenser in front of the radiator, but I do have a high clearance bumper and winch which disturbs airflow. And the radiator isn't anything fancy, just a rockauto TYC 1918.


Maybe try expiramenting and installing a temporary cut off switch to shut off the fans at 35mph or so and faster when it's real hot out. See if that makes a difference. Having the fans on at speed can actually hinder cooling performance if I recall correctly.

That's a lot of unnecessary complication for a simple problem. IMO the OP should revert to stock, advance a new Blue Clutch, and change out its oil with 10,000 or 20,000 CST weight. there's plenty of great write-ups here. You can always add the fans to the front of the AC condenser as pushers (but i think people really only do this to help the AC star cold)
 
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NLXTACY

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Well I hope you get it figured out.
I was thinking of getting a RD rad, I would run the stock fan. But the numbers you speak of are what I’m trying to avoid.
Ultimately I would like it get it to run under 200 in all conditions with the AC on.
Excluding towing.
In my turbo LX I have the RD radiator and have never seen temps above 196. My driving temp (as long as I’m not flogging it uphill) is 186. Modified fan clutch and stayed the original fan. I wouldn’t change this setup for anything.

619657AC-E7E5-4B98-A7B5-F48986CC08E7.jpeg
 

zonker

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Okay.. thanks for all the great responses. The Ron Davis radiator has been awesome.. I have written a lot of info about that. The problem I am having is when the A/C is on.. hot day and uphill. Hence the reason I was suspecting the electric fans.. they just don't move enough air. Otherwise the coolant temp is very low in just about all temperature conditions. It was a great experiment since I thought I was moving the cooling capacity up a notch. Apparently NOT. Also in the end it did not cost me a lot of money.. just lots of time solving several of the electrical problems that the harness dealt me.

SO I am going to "yard" out the SPAL fans and put my modified blue fan clutch and fan back in. The rest of the system is "pristine"and well sorted. Of course all the wiring and fans will come out a lot easier than they went in! Only thing I am short on is the shroud. Certainly I should be able find one no problem.. well at least I think that will be the case!
 

zonker

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In my turbo LX I have the RD radiator and have never seen temps above 196. My driving temp (as long as I’m not flogging it uphill) is 186. Modified fan clutch and stayed the original fan. I wouldn’t change this setup for anything.

@NLXTACY that was one of the posts that helped seal the deal. Adios electric fans. I too will "not change this setup for anything" again! But I had to try and waste some money. Guess it could have been spent more wisely at Wits-End!
 
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baldilocks

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Electric fans must be better because they make annoying noise, they are not factory original equipment (and this one is huge because everything aftermarket is better) and even more huge is that KOH race cars run electric fans on a “heat exchanger” mounted behind the driver and this makes electric fans super cool (no puns intended) so I think we should all buy a RD heat exchanger and mount it on the roof with quad electric fans powered by dual alternators powered by a 500hp V8 because Toyota got it all wrong in the first place.

This subject has been discussed at extreme length here and on every other car forum in the world for many years. Why do vehicles marketed to haul and tow not come with electric fans like civics and Camry’s do?
 

zonker

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Hence the reason that Ron Davis sells all kinds of heat exchangers.. I knew that going in. I was just in hopes that I could be"smarter" than everyone else here.. on other forums.. plus professional builders and make it work on an engine that produces average power for 4.5L.. my bad! :cool:

Quite a few of us have "stuff" on our LC's that is not Toyota nor officially approved updates and a good many of them have provided an improvement.. in some cases a substantial improvement. So be it with my trip down the rabbit hole with quality electric fans. I thought.. wrong. Oh well.. a half a day of labor to put things back to their happy place!
 

Broski

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Thanks Zonker for the well documented info on the Ron Davis radiator.
My main interest in this is being able to run the AC when Rock Crawling, don’t really care about heat exchangers on the roof and looking cool I want to be cool with the AC on.
If a RD Rad would make it so that I would never have to turn the AC off because of engine temps then I’m in.
 

landtank

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The only reason I've stayed away from the Ron Davis rad is that typically racing radiators partially achieve better cooling from designing a denser core. They can do this because the vehicle is designed to flow as much air through the engine bay that it can. So at racing speeds the positive pressure in front of the car helps move the air through the denser core.

By now most everyone knows that moving air through our engine bays is a challenge. People routinely complain about running hot on the highway and the AC not cooling when in stop and go traffic, both are air flow related.

I'm interested in seeing the results of moving over to a traditional fan and clutch setup and how the temps change.
 

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