[kingbuzzo]

Apparently yes you do...hopefully you don't go the redneck a/c route...lolz:

[dataway]

Hey, the Navy used those redneck AC systems for decades, probably still do. Pump 50 degree seawater through a heat exchanger and blow air through it.

[RocktimusPryme]

Super Cool information. I think the fact that companies kept using engine driven fans on heavy duty trucks well after most cars dropped them shows how well they perform in certain situations.

But to add to the conversation, I think people often don't frame the electric vs mechanical fan argument correctly.

Most people who have cooling issues on old cars with clutch fans, have them at stops and low speed traffic. Im not saying you can fix this, but to me, this is where an electric setup shines. They arent RPM dependant like an engine driven fan is. You can have all the beans the electric fan can provide at a low RPM where the engine driven fan cant spin faster than the water pump. At a certain point I don't know how much dead max airflow matters. Once its adequate, its adequate. The bigger decision point might be, which setup can give me the most airflow when I need it?

Now I have head horror stories of people going to electric fans and the problem flipping, all of a sudden they get hot at highway speed, but I think that is a matter of the shroud not letting enough air through. I think your testing shows that clearly, which the openings and the fans blocking said opening being an airflow limiting factor. Which is pretty easily fixed with those flaps that you see with some OEM shrouds and the higher quality aftermarket units.

Aside from the obvious mistake people make with buying inferior electric fans to start with, I think that is probably the biggest mistake people make in going electric. Shroud airflow at highway speed.

Side note. I have this enormous Bosch electric fan with shroud I bought from a swap meet for $5. I believe its from an early 2000s Mercedes C230. Its 19.5 inches, the same size as the big bad AC GM clutch fans. I can wire it to come on full blast, it even has a built in slow start. But it has 4 wires, a large ground and large hot, that I believe is meant to always be hot. Then another smaller wire when given 12 volts signals on. The 4th wire I assume is meant to be PWM speed controlled.

Ive been trying to figure out an easy way to make it work because I think it could be the new Lincoln Mark VIII fan if I can. I even bought a cheap PWM controller which I can make work when I put it on the big wires to control speed, but I think the speed should be controlled by that 4th wire.

[dataway]

To be honest, I think a properly designed electric setup is the overall best way to go. My 2011 GMC truck with HD cooling, HD everything ... has no mechanical fan and I have never seen it ever go over thermostat temp even for a second.

No constant parasitic draw, less noise (most of the time), lighter, and probably easier on the water pump as there is no fan shaft. And, as you say, it's cooling specifically WHEN you need it regardless of engine rpm.

But then the truck has a huge frontal area, big radiator, plenty of room under the hood, lots of flow at highway speeds. It's all about what a vehicle was designed to have. A GTO has in comparison a tiny frontal area, smaller radiator, and a large, high hp engine .... it needs a LOT of air flow, more air flow than the vast majority of electric setups can provide and limited space to work with.

Just imagine for a moment if some GM engineers decided they wanted to create an electric fan setup for vintage vehicles ... pretty sure it would work, probably way better than the original OEM mechanical fan.

Like most things ... implementation of the technology is as important, or more important than the technology used.

[Formulajones]

I did a bunch of real world testing in this area and came to my own conclusions.

Test subject was dads GTO with a 700hp 571 pontiac. Always ran cool with the stock clutch fan and shroud setup and a 4 core copper radiator.
When he wanted to step up to an aluminum radiator he wanted to try electric fans, mainly to remove the parasitic losses from a driven fan blade. (He's a HP junky)

I found the shroud construction is more critical than any type of fan used. If the electric fan setup is too close to the radiator and blocking large sections of the radiator impeding air flow it's just not going to work well. Air flow through just the fan area is simply not enough and turning the fans on to try and pull air through those tight blocked areas doesn't work well enough. Cutting openings in the shroud and installing rubber flaps with the idea that air will push through there at speed also doesn't work well enough.

What happened was an engine that normally ran in the 160's to 175 degrees now would climb to 190 and stay there with the electric fan setup. Even at highway speeds the fans would kick on and run constantly trying to pull air through the radiator, that was because too much of the radiator is blocked with the electric fan shroud setup and even the fans running full speed couldn't pull enough air to overcome it going 70 mph.
It did work well sitting still and would cycle the fans on and off but that scenario was only 30% of driving.

So I pulled the electric off, put the stock shroud back on with a 7 blade clutch fan and immediately the car ran cool, almost cold. Even when it's over 100 degrees here it never gets over about 182 sitting still idling. Once moving it's in the 170's and when it's cooler outside it'll run in the 160's no matter what you do, and highway speeds aren't a problem anymore.

You really have to spend a ton of money for a well designed electric fan setup to work properly. It's doable but at that point of the testing dad said screw it, the clutch fan does a great job, will never really fail, and in the end he has enough HP anyway he's not going to miss a few ponies. Running cooler in Arizona is way more important.

[Formulabruce]

As Data said in first post. It IS in the SHROUD. Any doubts look at 69-72 Grand Prix " Wind tunnel".
The homework was done Long ago...

[dataway]

For the DIY'er .. yeah, an electric setup just isn't ideal in our vintage cars without a huge investment. As for the HP, spend that electric fan money on some other goodie for the extra HP.

Yes I think electric is better ... but only for a vehicle designed from the ground up to have electric.

Our cars were built to have a mechanical fan ... so that's what works best.

A HUGE amount of engineering goes into the frontal area of a vehicle, aerodynamics, cooling air flow, cosmetics, impact resistance, noise considerations. To take a car that was designed to have a giant mechanical fan pulling huge amounts of air through the radiator and try to replace it with an electric system is just a big ask.

[HWYSTR455]

I've run those Flex-a-lite 295 fan setups on 68-72 A-bodies, they work, and were my go-to. They have a rating of 4600cfm, but don't believe all fan companies use the same formula to calc CFM.

I think the 295 fan is listed as a truck fan intended for towing or high demand.

The reliefs are a big factor, as it how much heat your engine produces. Like, a small displacement inline 4 isn't going to have the same heat production as a 571 tuned for max power.

There's many configs in between those two examples, so what works on one may not work on another.

The info in this thread certainly proves points targeting the shroud, and is great info. Next would be to calc the thermal heat (most likely BTUs) of a particular engine in several types of uses, like idle, cruise @X RPM, and WOT pass of X time.

With those data points you can calculate the requirement(s). That's the first step of selecting a fan.

Many vehicles calculation by OEs is by % of use in the categories of use, like 30%, 50%, and 20% for idle/cruise/WOT. So if you use a vehicle in WOT more than the 20%, it can overheat, because is would be a waste (design/packaging/money) to make a cooling system that exceeds the needs.

So if you add 100hp to your car, you 'might' exceed the existing cooling performance of your system.

Shrouds, you just choose the most effective one that fits always. And, in true nature of hot rodding, you probably should do the same for fans.

Just to comment, some fans will flow more than others, based on blade design (pitch/shape) and type of motor (freewheel drag). And some manufacturers give the rating of the fan alone, not including any reduction of flow of the shroud package as equipped.

So a listing of a shroud packaged fan setup that states '5000cfm' 'might' be based on just the combo of 2x 2500cfm fans individually and not including any waste due to poor shroud design.

This also doesn't account for any variation of how the fan' cfm was calculated. But as a general rule, you can tell by what the max amp draw is of the fan.

An informed buyer is a smart buyer.

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[Gator67]

The factory style clutch fan and shroud keeps the 535 in my 70 Formula cool, even with A/C on in Phoenix. However, on my latest 2nd gen bird project I'm going to run an electric fan set-up to cool a stroked LQ4...with the air intake tube, radiator hose, etc., just not enough room for conventional cooling fan, and a conventional fan would have ended up in an odd spot. The set-up I'll be running consists of two brushless SPAL 12" fans in a 3.5" thick shroud with two sets of reliefs/flaps. I like the idea of being able to run PWM controlled by the Terminator Max ECU, and the fans are very powerful, but I'm a little nervous that it won't keep up. Friends here in town have not luck with 2 x 12's, but those set-ups typically consist of weaker brushed fans which are wired so that they're either on or off (or one or both are on and off), and are installed in thin shrouds without any reliefs/flaps. To make those deals work, they have to use 14" or 16" fans, which, unfortunately, create additional packaging challenges (e.g., interference with steering box). I'm still a couple months away from the first start up...will report back.

[HWYSTR455]

SPAL brushless fans are excellent, and are PWM friendly. They are one of the most efficient fans on the planet.

Some of the newer OE fans actually have the PWM controller built into them.

I run the 'vette PWM controllers on my GTO, the Dominator ECU controls them.

The SPAL brushless fan motors are very flat, and make it easier to package in a tight engine compartment. Super efficient and freewheel effortlessly. But in some cases, the water pump snout can get in the way of 1 large fan configs, so 2 smaller offset fan motors is the only option. (That's how I ended up).

I wish I would have gotten the SPAL brushless fans, but somehow talked myself out of it. My setup does creep a little, and on a 180 stat I run 190, 200 with AC on. I think my problem is the rad, which is one of the Champion type aftermarket ones, so I recently got a Cold Case. If that doesn't keep it where I would prefer it, I will swap the fans out with SPALs.

I run the fans at 30% below 170, 170-180 at 40%, 180-195 at 70%, and then 95% up. I do a 10% bump when AC is on.

I had a variable of MPH too, and over 50mph I ramped them back up to 70mph where they would freewheel, but the motors and blade type must be enough of a restriction that I had to remove that. I thing with the SPALs I could add that back in.

Shroud is properly designed, spaced, and has reliefs.

I'd be interested in how you make out Gator67, please post your results once you get to that point.



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