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@sikryd Back to your problem. If you're mostly having trouble cooling while driving around (ie. engine speeds significantly above idle) you will move way more CFMs and therefore shed more BTUs of heat with a good shrouded mechanical fan, no question. This extra airflow in the engine bay will help a bit with your other heat sources but honestly the effect is negligible. If you're having trouble mostly in stop-and-go traffic when you're idling, you probably wouldn't be happy with a mechanical fan.

Why is the problem happening more with your aluminum heads? Well, I don't think it's just the aluminum conducting more heat to the underhood air. The factors for heat transfer are thermal conductivity and the delta T, the difference of temperature. You're on the right track by thinking aluminum has a greater thermal conductivity, it's ~2.5-3x that of iron depending on the alloys of both.

The outside of your head, where you figure the problem is coming from, let's say it's 210 degrees because you're running hot. Outside air let's say is 100 because Vegas, so we have a 110 degree temp differential and we have air which has notoriously lousy thermal conductivity. So sure, you're gonna shed a little heat from your new aluminum heads to the underhood air.

Let's look at the inside of the head though, you've got the combustion chamber at 700-1500?+ degrees dumping heat in to the aluminum head. Rough math, at 3x the conductivity of an iron head, it's losing 3x the BTUs from your chamber to the head than your iron heads did, and likewise moving way more heat from your aluminum head to the coolant (a much better conductor of heat than air).

So just by the head material change, you're dumping much more heat from your combustion chamber through the 3x more conductive head to your coolant. In my opinion, this would account for much more of your coolant temperature increase than engine bay airflow over your aluminum head surface.

What can you do? Well you're shedding heat through coolant > rad metal > air. Since air is a terrible thermal conductor, you have to move a lot of it, and this is where your biggest gains will be had. You either need a lot more surface area of rad (either bigger surface area or thicker core) or you need to move a lot more air. This is why I made the suggestion of a good shrouded mechanical fan, which does at first glance seem like a step backwards from super nice modern electrics. If your problem is at rpms where a mechanical fan can work effectively, I believe this will be your best bang-for-the-buck in terms of cooling system improvement. A couple hundred bucks would probably cover a cheap plastic shroud, OE fan clutch, and a heavy duty plastic fan easily.

I don't believe your idea to mount a couple electric fans underhood will do anything for your temps due to the previously discussed awful thermal conductivity of air and the mediocre flow rates of most electric fans.

Thanks for reading my midnight essay on cooling, hope typing this out quickly right before bed didn't result in it being too awful to read.
 
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You could get a mist sprayer to mist the radiator. Less and less efficient as the humidity rises. I imagine it would make the engine bay a mess, and really a mess unless using distilled water. Just pretend I didn't even mention it. ;)
 

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@sikryd Back to your problem. If you're mostly having trouble cooling while driving around (ie. engine speeds significantly above idle) you will move way more CFMs and therefore shed more BTUs of heat with a good shrouded mechanical fan, no question. This extra airflow in the engine bay will help a bit with your other heat sources but honestly the effect is negligible. If you're having trouble mostly in stop-and-go traffic when you're idling, you probably wouldn't be happy with a mechanical fan.

Why is the problem happening more with your aluminum heads? Well, I don't think it's just the aluminum conducting more heat to the underhood air. The factors for heat transfer are thermal conductivity and the delta T, the difference of temperature. You're on the right track by thinking aluminum has a greater thermal conductivity, it's ~2.5-3x that of iron depending on the alloys of both.

The outside of your head, where you figure the problem is coming from, let's say it's 210 degrees because you're running hot. Outside air let's say is 100 because Vegas, so we have a 110 degree temp differential and we have air which has notoriously lousy thermal conductivity. So sure, you're gonna shed a little heat from your new aluminum heads to the underhood air.

Let's look at the inside of the head though, you've got the combustion chamber at 700-1500?+ degrees dumping heat in to the aluminum head. Rough math, at 3x the conductivity of an iron head, it's losing 3x the BTUs from your chamber to the head than your iron heads did, and likewise moving way more heat from your aluminum head to the coolant (a much better conductor of heat than air).

So just by the head material change, you're dumping much more heat from your combustion chamber through the 3x more conductive head to your coolant. In my opinion, this would account for much more of your coolant temperature increase than engine bay airflow over your aluminum head surface.

What can you do? Well you're shedding heat through coolant > rad metal > air. Since air is a terrible thermal conductor, you have to move a lot of it, and this is where your biggest gains will be had. You either need a lot more surface area of rad (either bigger surface area or thicker core) or you need to move a lot more air. This is why I made the suggestion of a good shrouded mechanical fan, which does at first glance seem like a step backwards from super nice modern electrics. If your problem is at rpms where a mechanical fan can work effectively, I believe this will be your best bang-for-the-buck in terms of cooling system improvement. A couple hundred bucks would probably cover a cheap plastic shroud, OE fan clutch, and a heavy duty plastic fan easily.

I don't believe your idea to mount a couple electric fans underhood will do anything for your temps due to the previously discussed awful thermal conductivity of air and the mediocre flow rates of most electric fans.

Thanks for reading my midnight essay on cooling, hope typing this out quickly right before bed didn't result in it being too awful to read.

You seem to spend a tremendous amount of energy promoting mechanical fans, It almost seems you have stock in fan blades :ROFLMAO:

I must be reading and or understanding your essay incorrectly.

Aluminum heads and blocks transfer heat more efficiently and at a higher rate to the coolant, (I think you agree with this) Therefore the radiator will not be over tasked if it already performed adequately with the iron components that were replaced with aluminum (again I think you said that)

The vehicle that performed as desired in Hawaii but suddenly has issues remaining cool in Las Vegas is a much easier thing to diagnose. Set aside the fact Hawaii is at sea level and Vegas is above 2,000 feet The real tell is the moisture in the air, out there in the tropics that moist air is incredibly great at keeping his engine cool, (Kind of like that mister you suggested) Vegas has the driest air on the continent.

One other thing you commented on that might need a small correction. You anecdotal reference to big trucks still using mechanical fans is not quite on point. Sure large diesel trucks and buses retain mechanical fans to some degree but not all and both General Motors /Volvo Penta and Ford Commercial over the road platforms are now using electric fans as primary air movers. For exactly the same reasons automotive applications have moved over to it and it ain't some conspiracy to target the poor cottage fan makers of the North East.


Properly designed cooling systems built around sound principles and techniques will result in cooling capacities exceeding need and this can be done with electric air control. This is not opinion it is scientific fact and proven on every road going passenger vehicle built today. If a 800 HP Hell cat comes from the factory with electric fans...pretty sure we can cool a old shoe box Chevy with the same hardware.
 

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I would also suggest an oil cooler if you don't have one. I have one on my 1990 Ford F-250 that really does help keep the engine temp down when pulling a load.
 

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Boy, talking about going to left field........, but very interesting. I think I learned a lot.
 

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You seem to spend a tremendous amount of energy promoting mechanical fans, It almost seems you have stock in fan blades :ROFLMAO:
I actually prefer electric in most applications, but it's all about the right fit for the application. If you have a vehicle that produces a lot of waste heat, has heating problems at road speed, and a small rad surface area, mechanical is a good fit.

Aluminum heads and blocks transfer heat more efficiently and at a higher rate to the coolant, (I think you agree with this)
Yep. 100%

Therefore the radiator will not be over tasked if it already performed adequately with the iron components that were replaced with aluminum (again I think you said that)
No, what I was trying to say is that due to the higher heat transfer between the combustion chamber to head casting, you're shedding a LOT more heat to the coolant than with the iron heads. If you were testing with identical aluminum and iron heads (if there is such a thing) in an absolutely perfect laboratory environment, you'd see higher coolant outlet temps with the aluminum heads, slightly lower EGTs, and actually slightly less horsepower (very slight, every ~2500BTU/hr is 1HP).

So, a cooling system that worked fine but was maybe just borderline with iron heads can in fact be not enough with aluminum heads as more BTUs are being transferred to the coolant in the first place.

The vehicle that performed as desired in Hawaii but suddenly has issues remaining cool in Las Vegas is a much easier thing to diagnose. Set aside the fact Hawaii is at sea level and Vegas is above 2,000 feet The real tell is the moisture in the air, out there in the tropics that moist air is incredibly great at keeping his engine cool, (Kind of like that mister you suggested) Vegas has the driest air on the continent.
Very good point I didn't bring up. Moist air is a slightly less awful heat conductor than dry air. The difference between iron and aluminum thermal conductivity is 2.5-3x, while the difference between moist air and dry air is just a few percent even at 100F (104F = 40C in the chart below)

Slope Rectangle Plot Line Font


So while it will make a difference, if I had to bet on what's making the bigger difference, it would by far be the thermal conductivity of the aluminum. Also keep in mind the delta T between the radiator surface and air on that 100 degree day is maximum 110 degrees, while the delta T in the chamber is 300-1000+ degrees. The math gets more complicated than I care to get in to, but for hot rod math, close enough.


One other thing you commented on that might need a small correction. You anecdotal reference to big trucks still using mechanical fans is not quite on point. Sure large diesel trucks and buses retain mechanical fans to some degree but not all and both General Motors /Volvo Penta and Ford Commercial over the road platforms are now using electric fans as primary air movers. For exactly the same reasons automotive applications have moved over to it and it ain't some conspiracy to target the poor cottage fan makers of the North East.
I'll give you that, I'm not familiar with those 2 platforms. I just know every OTR tractor I've been around and every new 3/4 ton or 1 ton pickup I've owned or touched has had a mechanical fan.

Properly designed cooling systems built around sound principles and techniques will result in cooling capacities exceeding need and this can be done with electric air control. This is not opinion it is scientific fact and proven on every road going passenger vehicle built today. If a 800 HP Hell cat comes from the factory with electric fans...pretty sure we can cool a old shoe box Chevy with the same hardware.
Valid point, but break it down. The cooling system in a tri-five Chevy is not quite designed to the standard of the new Hellcat you're comparing it to. The new Hellcat you're talking about sheds FAR less BTUs of heat per HP to the cooling system than an old big block Chevy. BBCs are not exactly paragons of thermal efficiency, especially with aluminum heads. Also, take a peek at the rad of a new Challenger, it must be 2-3x as wide as that in a tri-five Chevy, tons of surface area. If @sikryd had a custom core support with a full width Hellcat radiator in, the electrics would probably be fine, even with the far less thermally efficient BBC.
 

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Mechanical robs power, in some cases up to 30+ hp. Proven fact. Pass...
That's the exact video I already responded to above. Apples to potatoes. Short form in case you're not one to read longer posts; mechanical fans use a ton of power at high RPM, because they flow a ton more air at high rpm. CFM costs HP. An automotive electric fan doesn't exist that moves the kind of air the mechanical does at 7000rpm because the motor would have to be industrial sized and draw hundreds of amps. If you're gonna disagree, please at least go read my original reply to that same video from last night first.
 

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No, what I was trying to say is that due to the higher heat transfer between the combustion chamber to head casting, you're shedding a LOT more heat to the coolant than with the iron heads. If you were testing with identical aluminum and iron heads (if there is such a thing) in an absolutely perfect laboratory environment, you'd see higher coolant outlet temps with the aluminum heads, slightly lower EGTs, and actually slightly less horsepower (very slight, every ~2500BTU/hr is 1HP).

So, a cooling system that worked fine but was maybe just borderline with iron heads can in fact be not enough with aluminum heads as more BTUs are being transferred to the coolant in the first place.
As my physics professor loved to say "There is no free lunch" and if a given engine produces X heat and produced Y power... the radiator has to deal with X+Y So swapping to Aluminum heads should in theory only increase the actual amount of heat by also increasing power.

FYI in all my years of hot rodding I have not seen Aluminum Heads of comprable size and design lose power and in fact straight across swaps of equal volumes and port,combustion chamber size has seen significant lower operating temperatures. (With measurable power increases to boot)

Valid point, but break it down. The cooling system in a tri-five Chevy is not quite designed to the standard of the new Hellcat you're comparing it to. The new Hellcat you're talking about sheds FAR less BTUs of heat per HP to the cooling system than an old big block Chevy. BBCs are not exactly paragons of thermal efficiency, especially with aluminum heads. Also, take a peek at the rad of a new Challenger, it must be 2-3x as wide as that in a tri-five Chevy, tons of surface area. If @sikryd had a custom core support with a full width Hellcat radiator in, the electrics would probably be fine, even with the far less thermally efficient BBC.

The Big Block Chevrolet platform in all it's iron magnitude is highly efficient in both heat transference and net power yields that are even to today's computer designed platforms respectable. Toss on a set of good flowing aluminum heads and it can make you scratch your head as you attempt to comprehend just how good that 47 year old design is.



My anecdotal illustration;

496 Aluminum CNC port match rectangular port heads 11 to 1 Compression. full roller cam 555 HP at the wheel and averaged 14.7 MPG for 5025 miles (Ca to Kentucky and Back) Electric fans only. Never saw more then 190.00 on the gauge.


Car Vehicle Motor vehicle Hood Light
Automotive tire Wheel Motor vehicle Hood Rim
 

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That's the exact video I already responded to above. Apples to potatoes. Short form in case you're not one to read longer posts; mechanical fans use a ton of power at high RPM, because they flow a ton more air at high rpm. CFM costs HP. An automotive electric fan doesn't exist that moves the kind of air the mechanical does at 7000rpm because the motor would have to be industrial sized and draw hundreds of amps. If you're gonna disagree, please at least go read my original reply to that same video from last night first.
I'll agree to disagree. 6 years building jet engines and turbo-prop engines gave me enough background to know that a mechanical is not as efficient. It is, however, important that the system be setup correctly, especially in shrouding and air diversion.

That flow comment isn't actually accurate. There is a limit to what a non-varisble pitch blade can push or pull. That is why planes have limits. For example, a turbo-prop plane will initially ascend quicker and steeper than a straight jet, but after that the straight jet engines are more efficient. Your theory is not accurate, if it were, C130s would be "hela fast".

You can disagree, but I'm still right :ROFLMAO: , after building them I spent 9 years flying.

Of course, I'm looking at this from a power perspective. Saying that, how is it that probably 99% of cars today, even performance cars, do so well w/o a mechanical fan? Technology has evolved, made the fans and controllers superior. They are now more cost effective to install, before they were not, and of course the car design helps, but the thought that stone age mechanical fans are better? Ehhhh....not seeing it.
 

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@Carson Blocks

I really enjoy conversing with you.
Likewise, I always learn something from our discussions and appreciate that you've got the engineering mindset as well. So much hot rodding is done on intuition and old wives tales and people wonder why they can't get stuff to work right. I always get concerned people will take these debates the wrong way and actually get upset when challenged.

As my physics professor loved to say "There is no free lunch" and if a given engine produces X heat and produced Y power... the radiator has to deal with X+Y So swapping to Aluminum heads should in theory only increase the actual amount of heat by also increasing power.
I disagree. Let's say the combustion chamber, combustion temperature and all other aspects are the same. Which engine is going to have more heat transfer from the very hot combustion chamber to the cooler cylinder head?

Aluminum at ~235-250 watts per meter Kelvin
- or -
Iron at ~60-80 watts per meter Kelvin

Font Material property Screenshot Parallel Number


The Aluminum head has to take more heat from the chamber. I was trying to stay away from formulas, but you've done physics so remember Fourier's law, q = -k Δ T.

q
= heat flux
k = thermal conductivity
ΔT = temperature gradient

If our ΔT is the same, and but our k has gone up by 3.5x, the heat transfer has to go up by 3.5x. All else being equal, the aluminum head has to absorb more heat from the combustion chamber than the iron, no two ways about it.

Where does the heat then go? Sure, a little of it is shed to the air, but most of it is shed to the coolant, then the radiator, then the air passing through the radiator. It just has to work this way, the laws of physics are pretty inflexible.

And to preemptively counter an objection, we both know that in this identical scenario the iron head is usually said in hot rodding wisdom to run "hotter". Yes, kind of. The surface of the head in the chamber is hotter because of the lower conductivity, it can't transfer the heat through the casting and to the coolant as efficiently. The very surface is hotter, but 1/2" below the surface, the iron head will be cooler.


FYI in all my years of hot rodding I have not seen Aluminum Heads of comprable size and design lose power and in fact straight across swaps of equal volumes and port,combustion chamber size has seen significant lower operating temperatures. (With measurable power increases to boot)
The difference would be well inside the dyno error. We both know how hard it is to get exactly identical pulls, even on the same engine controlling all variables. It takes ~2544 BTU/hr to equal 1 horsepower. You can shed a LOT of heat before seeing measurable results. Hot Rod did a test on this a while back, but I recall being frustrated that it wasn't near scientific enough to measure such a tiny difference without it being well absorbed in the margin of error. The guys at Westech are still alright in my books, but I don't think they ran the math on just how small of a difference they were looking to prove.

Back to physics for a second, if I sold you on the argument above that the aluminum head has to absorb more heat, that means the combustion chamber has less (very marginally so, almost immeasurably small. No free lunch in physics, remember? Less heat in the chamber, less force on the piston (no free lunch). The difference would be minute and you'd have to set up a heck of an experiment to see it, but it will be there.
 

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Back to the OP.

Glad the louvers worked. Get some good ventilation, get off the mechanical fans, get good airflow and air management (shroud and ventilation).

Basic rules of Rodding, take a look at what turbo guys do...there is your answer.
 

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I'll agree to disagree. 6 years building jet engines and turbo-prop engines gave me enough background to know that a mechanical is not as efficient. It is, however, important that the system be setup correctly, especially in shrouding and air diversion.
We can figure this out. Since electric and mechanical fans are completely different animals in regards to airflow, put aside common hot rodding wisdom and let's get dirty with the actual science for a minute.

Please explain how a fan blade of the exact specs, size, pitch etc. takes less energy to turn the exact same speed if an electric motor is turning it instead of a crankshaft? It can't. This is a concept we need to be 100% clear on before going any further. It's basic physics, which doesn't negotiate. The exact same fan blade running the exact same speed takes the exact same energy, it HAS to. Why are electric and mechanical fans so obviously different then? Because the blade profile, speed, shroud, cfm, everything about them is different. Apples to potatoes.

A really high end dual 11" electric fan setup like @sikryd has will only flow ~2700cfm on full. Mechanical cfm depends on shrouds etc, but 5000+ is not uncommon. If you do the math on what it takes to cause that huge 20-30hp loss at 7000rpm, you can get an idea of the insane cfm it's pushing.

An electric cannot do the same cfm as the mechanicals we're talking about. It just can't. You know how big a 20-30hp electric motor is right? A 20hp electric motor would take 1273A @ 12v to run (assuming no losses). That's not gonna work.

So why do we say an electric fan is more efficient? A few good reasons. It turns slower (around 4000rpm on high) and we both know there are more losses the faster you spin. That mechanical in your dyno video at 7000rpm is so far outside of its efficiency curve it's laughable.

So why do electrics usually work so good if we only have 3000cfm or less to play with? Because it can run at that 4000rpm regardless of what the engine is doing. Idling but hot? 4000rpm, no problem. You move less cfm and less btu/h, so you just do it over more time, easy. You also do it over more surface area, look at modern cars with the great wide crossflow rads. Don't need to have insane fans drawing huge power if you've got bigger fans and more surface area to draw across, and can run the fans at a steady 4000rpm as long as you like.

See why it's really apples to potatoes? One isn't better, they have different strengths, weaknesses, and each has applications it's better for. If electric fans were just better across the board, highway tractors where drivers would kill for half a mpg better would have electric fans, but they don't. C7 Corvette? Electric fan, obviously. Different applications, different 'best' fan for the job.

That flow comment isn't actually accurate. There is a limit to what a non-varisble pitch blade can push or pull. That is why planes have limits. For example, a turbo-prop plane will initially ascend quicker and steeper than a straight jet, but after that the straight jet engines are more efficient. Your theory is not accurate, if it were, C130s would be "hela fast".

You can disagree, but I'm still right :ROFLMAO: , after building them I spent 9 years flying.
I'm leaving the airplane stuff out as bringing in turboprops and jets is comparing apples to hand grenades. A jet engine is such a different animal we can't even draw a useful comparison.

Of course, I'm looking at this from a power perspective. Saying that, how is it that probably 99% of cars today, even performance cars, do so well w/o a mechanical fan? Technology has evolved, made the fans and controllers superior. They are now more cost effective to install, before they were not, and of course the car design helps, but the thought that stone age mechanical fans are better? Ehhhh....not seeing it.
We've beat this horse to death above, but again, look at the wide crossflow rads on modern performance cars and the area for big electric fans. You'd have to get out the plasma cutter to put that in a tri-five. Modern engines are more efficient as well, and shed less waste heat to the cooling system. In an era where every mpg and hp counts, engineers constantly tweak to waste less heat. They also don't want to give up the hp when you spike it to 6000-7000rpm. Better to keep those 4000rpm electrics turning away for longer, the modern cooling systems have enough thermal capacity to absorb the heat load and shed it over more time.
 

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@twin engines It's frustrating to try to have a debate if you're not going to read, and just post up random links. Politely, I'm not going to put the time in if you aren't.

That article doesn't negate anything written above, if you'd taken the time to read it. Of course you can gain efficiency by running electric fans at a lower rpm in the peak of their efficiency curve over a longer period of time. It doesn't mean they flow more CFM or that they magically turn with less energy input.

I mean this with all due respect, but you're not even trying to understand what I'm saying.
 

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We can figure this out. Since electric and mechanical fans are completely different animals in regards to airflow, put aside common hot rodding wisdom and let's get dirty with the actual science for a minute.

Please explain how a fan blade of the exact specs, size, pitch etc. takes less energy to turn the exact same speed if an electric motor is turning it instead of a crankshaft? It can't. This is a concept we need to be 100% clear on before going any further. It's basic physics, which doesn't negotiate. The exact same fan blade running the exact same speed takes the exact same energy, it HAS to. Why are electric and mechanical fans so obviously different then? Because the blade profile, speed, shroud, cfm, everything about them is different. Apples to potatoes.

A really high end dual 11" electric fan setup like @sikryd has will only flow ~2700cfm on full. Mechanical cfm depends on shrouds etc, but 5000+ is not uncommon. If you do the math on what it takes to cause that huge 20-30hp loss at 7000rpm, you can get an idea of the insane cfm it's pushing.

An electric cannot do the same cfm as the mechanicals we're talking about. It just can't. You know how big a 20-30hp electric motor is right? A 20hp electric motor would take 1273A @ 12v to run (assuming no losses). That's not gonna work.

So why do we say an electric fan is more efficient? A few good reasons. It turns slower (around 4000rpm on high) and we both know there are more losses the faster you spin. That mechanical in your dyno video at 7000rpm is so far outside of its efficiency curve it's laughable.

So why do electrics usually work so good if we only have 3000cfm or less to play with? Because it can run at that 4000rpm regardless of what the engine is doing. Idling but hot? 4000rpm, no problem. You move less cfm and less btu/h, so you just do it over more time, easy. You also do it over more surface area, look at modern cars with the great wide crossflow rads. Don't need to have insane fans drawing huge power if you've got bigger fans and more surface area to draw across, and can run the fans at a steady 4000rpm as long as you like.

See why it's really apples to potatoes? One isn't better, they have different strengths, weaknesses, and each has applications it's better for. If electric fans were just better across the board, highway tractors where drivers would kill for half a mpg better would have electric fans, but they don't. C7 Corvette? Electric fan, obviously. Different applications, different 'best' fan for the job.



I'm leaving the airplane stuff out as bringing in turboprops and jets is comparing apples to hand grenades. A jet engine is such a different animal we can't even draw a useful comparison.



We've beat this horse to death above, but again, look at the wide crossflow rads on modern performance cars and the area for big electric fans. You'd have to get out the plasma cutter to put that in a tri-five. Modern engines are more efficient as well, and shed less waste heat to the cooling system. In an era where every mpg and hp counts, engineers constantly tweak to waste less heat. They also don't want to give up the hp when you spike it to 6000-7000rpm. Better to keep those 4000rpm electrics turning away for longer, the modern cooling systems have enough thermal capacity to absorb the heat load and shed it over more time.
Go read up on variable pitch inlet guide vanes in jet compressors and variable pitch propellers on turbo-prop engines. That will give you the answers you don't have.

Rolls-Royce Allison and General Dynamics have a lot of good courses and books, and over 80 years proving what I said.

Run your mechanical fan friend. I will stick to modern tech and jet propulsion experience.
 

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@twin engines It's frustrating to try to have a debate if you're not going to read, and just post up random links. Politely, I'm not going to put the time in if you aren't.

That article doesn't negate anything written above, if you'd taken the time to read it. Of course you can gain efficiency by running electric fans at a lower rpm in the peak of their efficiency curve over a longer period of time. It doesn't mean they flow more CFM or that they magically turn with less energy input.

I mean this with all due respect, but you're not even trying to understand what I'm saying.
Mechanical fans push more air at higher RPM, but they reach a point of capacity where they overrun themselves and overtax the engine, creating more strain and more heat. Electric fans may not push as much at the higher RPMs and they too reach a point of limitation, but they do not creat drag on the power plant or generate the resistance on the engine, or heat from drag. That CFM you are referring to is inefficient and costs too much on the backend to be worth it, especially in a performance application.

You're not totally incorrect, but you have flaws in the end result of your conclusions.
 

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All this discussion about the conductivity of aluminum, steel, dry air, humid air, etc. is not all that meaningful. There are 3 kinds of heat transfer - conductive, convective, and radiant. Fans and airflow are convective heat transfer, as is the heat transfer from engine blocks and heads to coolant liquid. Convective heat transfer is more dependent on surface finish and surface area. The main place where conductive properties affect conductive heat transfer are cylinder walls to coolant, as well as combustion chambers to coolant. Those are very efficient no matter what the materials are so while they matter, it's not what matters most.
 
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