Electric Fan Size

[jlewis]

I got the impression from many threads that I have read that the general consensus was one large puller fan was better than two small fans.  I have always aimed at getting a Davies Craig 16", and now that I am actually doing the shopping I noticed that from Spal a dual 11" can produce more airflow than a high-performance 16".  What gives?  To give you an idea of what I am looking for, my cooling issues only occur at idle in traffic, and coincided with the installation of a condenser in front of my rad.

Thanks.

Jeremy.

[jlewis]

I might as well add this question at the same time; if I double up on Davies Craig fans (or any for that matter), can I double the airflow?

[Ash]

You really need one with a shroud. It'll help much more again. See if you can go and score a BF Falcon one. I have one put aside for mine and it is a very close fit to my rad. I just need to make a way to mount it.

BA and earlier used twin fans. BF and same very late BA MKII's, also the same era Territory's got the new upgraded single fan.

[R_Beckhaus]

You've got a condenser fitted in front of your Rad. Does this mean you've recently had the car air conned? does it spit out coolant each time you drive it also? My '68 was recently air conned with a condenser in front of rad. and started heating up and dumping coolant. Turns out the air con guy changed the thermostat to a 192 deg instead of the proper 182 deg. Took months of searching to realise wot happened. Changed back to correct thermostat and all is cool'n'groovy again. Just a thought as to your problem's cause.
Cheers, Ron B

[jlewis]

Ron,

Checked the thermostat much earlier on, tested, replaced, went as cool and high flow as possible.  No real difference.  I don't spit coolant very often.

[StephenSLR]

the general consensus was one large puller fan was better than two small fans.

According to Davies Craig their 16 inch pulls more cfm than two of their 14 inch fans.

The 16" does have a shroud whereas the 14's are just on supports and the 16 has a big f-off motor.

I have one in the Torana with a triple core, never have an issue with it, motor is a 308.

I have a 302 in the Mustang with 351 heads, not sure what radiator this is.



It has a pulley fan with no shroud, it has yet to heat up and I've driven it in heavy traffic.

s

[gbx78]

I got the impression from many threads that I have read that the general consensus was one large puller fan was better than two small fans.  I have always aimed at getting a Davies Craig 16", and now that I am actually doing the shopping I noticed that from Spal a dual 11" can produce more airflow than a high-performance 16".  What gives?  To give you an idea of what I am looking for, my cooling issues only occur at idle in traffic, and coincided with the installation of a condenser in front of my rad.

Thanks.

Jeremy.

ive been reading into this also .. a shroud will help alot .. but i also read that twin fans (ie 2 smaller ones but still decent cfm) with a shroud is better for crossflow radiators (radiators with the tanks on either side) and a single big fan for down flow.. i read this in a mustang mag article.. (not sure how viable source that is :P )

 The radiator i have is a double pass crossflow with inlet/outlets on the same side (due to accessories clearance issues on the other side). There is a baffle in the middle of the tank with the inlet/oultets which forces the water to go to the otherside before returning.
 
So a twin fan offsett in a 1inch thick shroud (one at the top and the other down the bottom) following the flow of coolant in theory generally makes sense?? but i dont know if it really makes much difference. ??

I have bugger all room between my radiator and the accessories on the engine.. so the bigger cfm single fan you go the thicker they are even for SLIM line ones. So 2 fans with slightly lower cfm (than a big single fan cfm) each and a shroud might be the way to go for me..

i could be way off in my theory lol . but thought id throw it out there incase it helps with the discussion

Im interested to hear what others have or using. Nothing beats proven examples.

[Ash]

Ok, Dr Karl experiment time. 

This may not answer all questions but it may give a little insight to some differences.

Here we have 4 Falcon thermo fans. Starting top left is EL. To the right of it is AU. Bottom left, BA. Bottom right, BF.



EL



AU

Biggest reason to choose AU over the EL, is the plug is on the same side as the battery, so no need to run as many wires across the rad support. Other wise the fans are better located but not a whole lot of difference than that.



BA

Almost the same as AU but the mounts are slightly differently placed and it has a location, screw holes, top centre for the V8 power steering reservoir to be mounted



BF

A different animal all the together. And this was the upgrade. You can see just how much larger the fan is and how much more coverage it has over the radiator itself.



Here they are lined up EL left through the BF on the right. Yes the single fan is wider which may be an issue for you, gbx78



Here is the alloy rad from from 69 R-code. It had the Davies Craig style fans mounted but I have removed one. You can see how little coverage they have compared to a fan with a shroud



The other down side is the damage they do. They mount by pushing a plastic pin through the rad fins and damage and rub through.







Here you can see how close of a fit the BF fans are to the rad

[gbx78]

Ash is that your personal collection of fans and shrouds??   

if so can you tell me how thick each is? and at what point that thickness covers.. like say its 4inchs but hats only at the fan motor then from there it tapers thinner.. if that makes sense..

oh and what sizes are they?? i think i have 20"x18X" approx of core.. id be curious to see if something like this could work for me too.

yes i have clearance issues but not ALL around .. just in certain areas like crank pully .. accessories up top .. so there is room in between here and there should something protrude within small spacers and as long as the rest of it tapers back  etc..

anyway sorry to hijack the OP ..

EDIT: i know cost is always an issue and money is scarce these days . .but as far as the product goes .. for me.. ive come up with these options (not necessarily from these sellers) but the thickness and capacity and size suit.. not sure if these help anyone:

http://www.ebay.com.au/itm/Derale-Performance-Electric-Fan-Dual-Speed-2400-cfm-DER-16822-/251064672962?pt=AU_Car_Parts_Accessories&hash=item3a749ee2c2&_uhb=1

http://www.ebay.com.au/itm/Derale-Performance-High-Output-Rad-Electric-Fan-4-000-CFM-Puller-13-Dia-Dual-/390580171747?pt=Motors_Car_Truck_Parts_Accessories&hash=item5af06473e3

http://www.ebay.com.au/itm/Derale-High-Output-Single-RAD-Electric-Puller-Fan-with-Shroud-18-DER-16818-/360632521736?pt=AU_Car_Parts_Accessories&hash=item53f75f9408&_uhb=1

or even this and then have a shroud fabricated to suit the radiator:
http://www.ebay.com.au/itm/Zirgo-ZFB16S-16-3000-CFM-High-Performance-Radiator-Cooling-Fan-Black-/271029787022?pt=AU_Car_Parts_Accessories&hash=item3f1aa2598e

[Veronica]

The area of a circle with a 16 inch diameter is is about 201 square inches, while the combined area of two circles with 11 inch diameters is about 195 square inches. Plus, fans do not pull uniformly across the entire surface area. The closer to the center you get, the slower the blades are moving in surface feet per minute. The dual fan will have twice the 'dead area' that a single fan has with similar diameters of motor housings, and the range from 11 inches out to 16 inches on the single fan will be moving faster than any part of the 11 inch fans if they are turning at the same speed in RPMs. With the single 16 inch fan you have larger surface area coverage, smaller dead zone, and faster moving outer band. By my reckoning, these facts would override any claims made by a person that is trying to sell me something. 

[gbx78]

The area of a circle with a 16 inch diameter is is about 201 square inches, while the combined area of two circles with 11 inch diameters is about 195 square inches. Plus, fans do not pull uniformly across the entire surface area. The closer to the center you get, the slower the blades are moving in surface feet per minute. The dual fan will have twice the 'dead area' that a single fan has with similar diameters of motor housings, and the range from 11 inches out to 16 inches on the single fan will be moving faster than any part of the 11 inch fans if they are turning at the same speed in RPMs. With the single 16 inch fan you have larger surface area coverage, smaller dead zone, and faster moving outer band. By my reckoning, these facts would override any claims made by a person that is trying to sell me something. 

that makes alot of sense, thanks for sharing!! right then a large single fan it is!

[Ash]

Ash is that your personal collection of fans and shrouds??   

Yes, but I have more of each. About the only ones from these I don't want are the EL ones. The BF fan is put aside for my 69. And the rest I have a plan in mind for another project. I sell a lot of Falcon stuff so get them often.

No worries, personally I'd go the single fan so will get some more measurements of it for you.

[gbx78]

Yes, but I have more of each. About the only ones from these I don't want are the EL ones. The BF fan is put aside for my 69. And the rest I have a plan in mind for another project. I sell a lot of Falcon stuff so get them often.

No worries, personally I'd go the single fan so will get some more measurements of it for you.

yes please.. that would be good. single fan measurements is all i need when you get time. cheers

[Veronica]

What I said earlier was with the assumption of everything else being equal. There are other factors, like blade width, angle, curvature and configuration to consider, but, those also tend to work in favor of the larger, single fan. They have wider blades generally, and that gives more acceleration time for the air, kind of like a rifle compared to a pistol. The longer barrel generates higher velocities. The wider blade also gives you more room for curvature in the blade. If the leading edge is nearly parallel to the radiator and the tailing edge is nearly parallel to the center line of the car and you have a longer run for the air to make across the surface of the blade, the air gets sling-shotted (is that a real word?) out the fan more quickly than it would on a narrower blade with the same basic configuration. Fans don't have blade curvature quite that extreme because the blades aren't wide enough to efficiently accomodate that, but, that is kind of what they are shooting for as an ideal. 

[Ash]

yes please.. that would be good. single fan measurements is all i need when you get time. cheers

No sweat. I'm just cruising around the house with the kids and dog. Got my boy to help me here. The dog however was not helping even though she thought she was. 

The fan blade diameter



Shroud width





Shroud height





The set-back, if that's the best way to put it, of the fan motor. This is with the tape measure on the very front of the shroud



But the shroud over hangs the top of the rad a bit by this much so you could take this measurement off the previous photos. This is against the point where the fan assembly would butt against the rad.



Fan centre from left side





Top of fan is this high above shroud



Bottom sits almost flush with shroud

[gbx78]

detailed measurements! great thanks. I shall have a look and do some more measuring on myside to see how i go.. cheers mate

[Ash]

My pleasure. Hope it may help in some way. 

One thing more I should mention in regards to the Davies Craig vs a shrouded fan. I some time back was having heating issues on a 351C in an XF. It was running twin Davies Craig fans. I swapped to a set of EL shrouded fans and gained 5 degrees celcius cooler across the board. It helped a great deal. It wasn't the end of my issues with that car but that's a whole other issue not related to fans.

[StephenSLR]

Isn't it better to have the fan on the left lower so it's near the inlet? That way it cools the water as soon as it hits the cores.

Also the Davies Craig 16" has a small shroud around the perimeter of the fan without all that plastic to the sides.

That BF one looks monstrous compared to this.



s

[Ash]

Isn't it better to have the fan on the left lower so it's near the inlet? That way it cools the water as soon as it hits the cores.

There were two fans on that rad. One, the left, was removed. I was showing the damage they Davies Craig fans do.

Also the Davies Craig 16" has a small shroud around the perimeter of the fan without all that plastic to the sides.

That BF one looks monstrous compared to this.



s

There's no air being forced through any of the unshrouded areas on that one. The only force given is by the car in forward motion forcing the air through.

[StephenSLR]

There were two fans on that rad. One, the left, was removed. I was showing the damage they Davies Craig fans do.

Yeah, some people fabricate a support so the fans doesn't bolt through the cores.

My mistake, the hot water comes in from the top. I just remembered I put my fan closer to the top hose (not bottom hose) on the Torana but being 16" it's almost in the centre anyway.

There's no air being forced through any of the unshrouded areas on that one. The only force given is by the car in forward motion forcing the air through.

Correct.

I haven't had any issues with that set up, the fan does the job very well.

You can also have a fan in front and one behind if you're radiator isn't big enough for two side by side and you offset them so they cool as much separate area as possible. The fan in front has to be flipped around and the polarity changed in the wiring so it rotates the other way.

Looking at the Davies Craig site, they now have 14" in Hi flow and Hi Performance, when I got mine they only had 14" in slimline which doesn't have much of a shroud.

s

[Ash]

I haven't had any issues with that set up, the fan does the job very well.

This is all that really matters in the end.

My F-truck's radiator is that big it rarely turns the thermo fans on. The fans don't cover it completely and in this situation, a single Davies Craig fan would do the job easily.
I have the thermo switch turned right down otherwise it runs too cool for the LPG ECU to be happy with the running heat range.

[StephenSLR]

I have the thermo switch turned right down otherwise it runs too cool for the LPG ECU to be happy with the running heat range.

Yep, fans are only for sitting in traffic, once you hit the highway the airflow is enough, if it overheats on the highway then your radiator is too small, there's a blockage or some other issue with the cooling system.

Edit: ^ for a street car that is.

s

[Petey]

I think it's more important to have the right sized radiator. One fan or two is going to make minimal difference if the radiator is too small.
My '67 fastback has a new cross flow radiator based on the one used in '67 and '68 big block Mustangs. This is a triple row unit which is thicker and much bigger in area than the original radiator fitted to a 289 engine and it bolts straight up using the standard big block radiator support brackets. Mine has the AU Falcon twin thermo fans fitted with a 195 degrees thermo switch in the top radiator hose and a 185 degrees thermostat.
Over this recent summer I took the car to the Tocumwal Hot Rod run where it performed flawlessly in 40 degress heat. The thermo fans worked overtime when idling and slow driving around in the street cruise (under 40kph) but according to the temp gauge never got past 205 degrees at worst. Once out on the highway at 100 kph the temp was constantly around 195 degrees which suggests the thermostat and radiator did their job well. The fans only came on intermittently and usually ran for less than a couple of minutes.
I chose the AU fans because they gave just enough clearance for the water pump spindle plus the serpentine belt system I have.  Because it was close, I used Ron Morris adjustable engine mounts to move the whole drive line back 1/2 inch just to be sure. Now there is at least 3/4 inch clearance from the fan cowl to the water pump. The good thing with twin fans is you can wire them so one fan comes on with the AC compressor which also helps keep the temperature down and uses less current.

PT

[StephenSLR]

The one I have ^ is a Northern.

http://www.northernfactory.com/HIGH_PERFORMANCE/SEARCH_BY_VEHICLE/FORD/MUSTANG

s

[Ausjacko]

On the '67 the core size was 620mm across.  On advice from forum posts, I used a ford mondeo twin fan set-up like this



This was go number three after the large 16inch fan did not fit due to depth and the two fans without shroud did not pull the temp down enough.

I did have a series II jag and used a set of EL falcon fans on that.  I understand the jag radiator fits quite nicely in our cars