[Formulajones]

Originally Posted by Sirrotica

The idea has been thrown out there that the car manufacturers changed over for fuel mileage reasons, but until engines were mounted transversely in a chassis, very, very few cars had electric fans. Obviously there is no way a mechanical fan can be driven by the conventional transverse mounted engine so enter the electric fans.....

Just for interesting conversation, your heavier 3/4 ton and up and even some of your 1/2 ton trucks today still don't use electric fans. Seems the vehicles that are destined and designed as a work horse for towing and hauling, still use big ole' mechanical clutch fans and shrouds. That says something.

My Duramax has a mechanical clutch fan on it, and my fathers newer 3/4 ton gas engine also has a mechanical clutch fan. My Duramax also has a factory 180 temp primary thermostat and the secondary is a 185.

[dataway]

My 2011 GMC 1/2 ton ordered with HD cooling, tow package, 3:53 rear, up front has radiator, AC condenser, PS cooler, tranny cooler and oil cooler .... has two electric fans.

What is strange is they almost never come on. They both came on only once since I've owned it, towing up a hill with the AC on in August. On hot days one of them will come on every few minutes in traffic.

[Formulajones]

Dad's 2014 Chevy 3/4 ton with the 6.0 gas engine and all the tow goodies, mechanical clutch fan.

[ta man]

Originally Posted by Firebob

I was thinking the same thing about the size of the fans but if you do 15" X 3.14= 47sqin(approx what I have now) and then 2x (12" X 3.14)=75sqin(approx). Seems like quite a bit more surface area getting flow with two smaller fans. As long as they were in a well fitting shroud for the core I think it might make a significant difference. Can't be sure without a trial. But math usually doesn't lie.

Your math is incorrect..area of a circle is pi(r)squared

3.14 x (7.5 x 7.5) =176 sq inch for the 15 inch

2 x 3.14 x (6 x 6) =226 sq inch for the dual 12 inch

[Formulajones]

Can you even fit dual 12" fans on a small 23" by 17" core???

They would almost have to be custom fabbed and diagonal of each other to squeeze them in there?? Probably not much, if any, room left for a shroud.

Because we had dual 12's on dad's radiator which is an Abody core that is 28" wide and there wasn't much more room. They make 13.5" fans for this size radiator and that's about all that fits as a pair as far as I know. They pretty much take up all the space there is by the time you design a shroud around them.

[dataway]

Actual square inches of fan surface is fairly meaningless.

Consider ... the hub area is basically useless when it comes to moving air ... two fans have twice the hub area.

Blade tip speed is important ... single larger fan can have more blade square inches traveling at a higher average speed for the same rpm compared to two smaller fans.

Single larger fan often has more room for a larger blade and greater blade pitch ... which moves more air.

So ... while it's perfectly possible two fans move more air ... it's not as simple as square inches of fan coverage.

[Tom Vaught]

Originally Posted by dataway

Actual square inches of fan surface is fairly meaningless.

Consider ... the hub area is basically useless when it comes to moving air ... two fans have twice the hub area.

Blade tip speed is important ... single larger fan can have more blade square inches traveling at a higher average speed for the same rpm compared to two smaller fans.

Single larger fan often has more room for a larger blade and greater blade pitch ... which moves more air.

So ... while it's perfectly possible two fans move more air ... it's not as simple as square inches of fan coverage.

TRUTH (with smaller turbos, they typically have to run at a higher rpm (due to the efficiency of each compressor wheel being in the 65% to 75% range. A larger Turbo Compressor can run at a lower rpm efficiently.

A vehicle fan blade follows the same "air flow physics" as a Turbo Compressor. Pitch being a large determinate.

Tom V

[Firebob]

Ok,obviously I'm no math wiz. And now that I think about it you may be right about the shroud not being strong enough at the center part using dual 12" fans even mounted diagonally. It might have to be dual 10" after all. Might be better off with a 17" single that would cover al the tubes top to bottom even if it's only 1/2-1/3 of the middle of the core.
We're getting there.
As far as the amperage draw...it's possible I'm feeling a contributing factor of going from a 37a stock alt to the 140a alt that I have now and dealing with going to elect fans at the same time. I know the new alt makes a lot more noise that's for sure.
While we're on it, curved or straight fan blades?

[Steve C.]

From SPAL.....

Q. What's the difference between the straight blade fans and the curved blade fans?

A. The straight blade fans provide maximum cooling for their size. The curved blade fans sacrifice a small amount of performance in return for a much quieter fan. If noise is an issue, go with the curved blade fans. If ultimate performance is the objective, use the straight blade fans.

https://www.a1electric.com/spal/faninfo.htm


Straight vs. Curved Fan Blades - Dispelling the Myth!

https://daviescraig.com.au/blog/stra...lling-the-myth


The revolutionary, patent-pending Flex-Wave™ electric fan from Flex-A-Lite® has greater airflow, is more efficient and is quieter than traditional S-blade and straight-blade designs. The Flex-Wave fan moves up to 20 percent more airflow than Flex-A-Lite Trimline fans, and up to 25 percent more airflow than the comparable electric fans from the competitors!

https://www.youtube.com/watch?v=apmv9p4jajM



Another tid bit when shopping for electric fans...........

There is no common industry standard for rating electric fans. Most companies use a cfm rating, often expressed in free-flow and not when placed behind a radiator. You can never know for certain about different cfm ratings or how a company has rated their fan since they can be tested by different criteria and methods. In comparison between brands using cfm ratings alone is difficult, typically not apples-to-apples.


( Information provided in this post does not represent a product endorsement. And unless specified it is not based on personal experience and is offered for general interest only )





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[68azbird]

Originally Posted by Firebob

That thought is what stopped me from changing it out. I think my next step will be to pull the elect fan and go back to a belt driven. But, of course that puts me right back where I was when it overheated in the cruise lane last year so I'll not stop there. Following that I think the WP is coming off and I'll do some internal inspections of the divider plates and the cooling tubes/rubber cups to make sure everything there is in order.

This engine has probably 5 thousand miles on it. Everything was done so I know it circulates as good as it can. Radiator is new 4 core brass w/waffle core design( whatever that does). Don't know if I would gain anything by going to a big alum radiator but it may be in cards. Does anybody think a pusher fan would help. It'd be an engineering feat to mount one because of the AC core but if it helped I'd make it happen.

Someone mentioned having the right space in between the shroud and the fan tips. I always figured the least space the better. Not so?

its 113 degrees here in AZ right now. i can take my bird out for a drive right now and drive it for 5 hours and not overheat with factory shroud and clutch fan and 4 row copper brass radiator.

[68 Firebird]

with all the info involved with electric fans I have to say FUHWEY. Gonna stay with the mechanical and be happy. Mine is happy with 180 stat!!! and life is short. Good Luck to OP. Gerry

[Firebob]

Cool. Straight it is. 17" fan( if I can get it ) in a good shroud.
When talking about clutch fans and fixed mech fans, a clutch fan will not offer any more air flow at low speeds than a mech fan. It's only when spinning faster that any kind of improvement might happen, correct. My heat issue lies in the low speed function so a compare able fixed fan would be more help for my situation. Just thinking out loud.

[Grand73Am]

Originally Posted by Firebob

When talking about clutch fans and fixed mech fans, a clutch fan will not offer any more air flow at low speeds than a mech fan. It's only when spinning faster that any kind of improvement might happen, correct. My heat issue lies in the low speed function so a compare able fixed fan would be more help for my situation.

A thermostatic fan clutch, which is what they came with from the factory, engages when it's needed, sensing the temperature coming off of the radiator. When it's engaged it's working like a fixed fan. So, if you're heating up in slow speed traffic, it will be engaged, like a fixed fan would be. But, when you're cruising along on the interstate, with the radiator being cooled by the flow of air through it at speed, the clutch disengages, and the fan freewheels, basically not using any engine power at this point, becoming quieter, and you might save a few drops of gas. A fixed fan can't do that.

[Bruce Meyer]

Originally Posted by 68azbird

its 113 degrees here in AZ right now. i can take my bird out for a drive right now and drive it for 5 hours and not overheat with factory shroud and clutch fan and 4 row copper brass radiator.

Same here with the A/C on. The factory had it right.

[Tom Vaught]

If you are into Electric Fans, SPAQ makes some good stuff, and has some great info.
Thanks Steve for the Links.

Tom V. .

[STEELCITYFIREBIRD]

We run the 17" version of this fan:
http://www.race-fan.com

, 3 blades on the circle car with a HTD belt/pulleys, ((elminates high RPM slippage possibility, not sure of current the pulley ratio off hand).
And A well fitted tunnel shroud. . We ran the 19" 3 blade version last year and a larger rad, was overkill. downsized it on new car due to engine placement No thermostat or restrictor disc.


This fan/shroud will hold the thick plastic sheet warm up board to the rad with the car idling! ....That's some serious air flow at idle. At 7k+...its a hurricane. There is no opening in the front of the car and the nose is sealed to the track. 190-210 in the worst air running wide open all the way around.drops right down to 170-180 cruising under caution. Probably could run 2 blades but like the head room in case rad screen gets restricted.

Point is...AIR FLOW thru rad cools engines.
I have a pile of fans and this is the best/lightest/most versatile by far. Blades are same material semi truck fans are made of.

I'll post a pic of the setup asap.

[Steve C.]

And on the subject of "race fans". I've posted this tid bit before from Circle Track magazine, related and maybe of interest. However it is very dated material......

When they used a mechanical fan, years ago many Winston Cup teams use an inexpensive stock four-blade Ford fan. This four-inch Ford fan, originally built for trucks more than 30 years ago, has proven to be the most efficient and economical mechanical fan on the market. Most teams use it for short-track. The type of track often determines what type of fan, for the super speedway most prefer to use electric fans because of the horsepower and fuel-efficiency advantages. In this situation they could potentially gain 15 percent in horsepower and possibly one to two miles per gallon in fuel.


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[Firebob]

Again, fellas, stock design is awesome when installed on stock components but when you vary from what the factory did it doesn't take a genius to figure that other upgrades are going to be necessary to keep up. I'm happy that you can run all day long in the desert heat and Your car not break a sweat. I cannot, apparently. Hence the journey of discovery.

Now, one 16"( seems to be the most common size) or one 12" and one 10"( 23" wide core)? Might have to stagger them just a hair. The cool thing is I could wire the duals separately. The single is on/off. Seems like the cost is about the same either way. So it's just an efficiency issue for me. Once I have exhausted all avenues with the elect fans and if I have not remedied my situation I will move to the radiator. I'm nothing if not determined.

[Formulajones]

I think we've all deviated from stock engines to some degree Bob. And yes anytime you make more power you create more heat.

I think my father went to the extreme side of things. My Cold Case post is a good read if you get time. For him, with 571 cubes and 724 HP, I didn't think that engine had a real good chance of running as cool as even a rambunctious 455. Yet the stock fan shroud and clutch fan has shown to be the best setup on it to date. No need to upgrade that. Matter of fact electric fans only made it worse. It's running so cool now, even cooler than smaller engines with less HP in a lot of cases, and we are in the same desert heat.

[Formulajones]

Originally Posted by Firebob

Cool. Straight it is. 17" fan( if I can get it ) in a good shroud.
When talking about clutch fans and fixed mech fans, a clutch fan will not offer any more air flow at low speeds than a mech fan. It's only when spinning faster that any kind of improvement might happen, correct. My heat issue lies in the low speed function so a compare able fixed fan would be more help for my situation. Just thinking out loud.

Just for conversation sake, and my test was by no means scientific, actually I was just joking around with dad when I did it.

When I finished the stock shroud and clutch fan install, he fired it up. Just sitting there idling in the garage I could tell it was already moving an immense amount of air compared to the electric fans I just pulled off. I took a piece of paper and held it a few inches away from the nose of the car, and it sucked it flat up against the grill with force when I let go. It even sucked the paper up against the lower valance opening when I put it down there. The dual electric fans didn't do that.

On a side note, the clutch fan works so well in this case, it's actually pulling his engine down to 150 degrees when at a slow crawl, and even sitting still idling it hasn't crept above 160 when it's 95 degrees outside. The electric fans wouldn't even pull it down below 190 when it was 85 degrees outside, lol.

Not trying to sway you, just hoping you find a solution.