Sizing radiator fans

If running with no shroud of any kind, just mounting slim fans on your radiator, do you want to size your fans to try to cover as much as the radiator as you can? Or does that end up impeding airflow too much while the fans aren't running?

Radiator core is 15.75" x 25.5"

Do i want two 12" fans, or two 10" fans?

Flow (CFM) is important, too.

If you have room otherwise (depth, etc.), I'd go with the larger fans.

I'm working on the radiator/fan situation in my Valiant. The biggest problem is not horizontal, it's longitudinal. Long engine, short nose, and now a thicker core.

Anyone got a big shoehorn?

Cover as much as you can, and use the fattest fans you can. When fans aren't running, they don't impede much airflow as they're mostly empty space.

Shrouds make a huge difference.

sounds like you need two fans, Slant.. or a pusher in front of the radiator

Keith Tanner wrote: Cover as much as you can, and use the fattest fans you can. When fans aren't running, they don't impede much airflow as they're mostly empty space. Shrouds make a huge difference.

Ok cool, that's kinda what i was thinking based on the shroud/fan setup i got from you guys for the MSM, but i didn't know if the theory changed once you were talking about a setup with no shroud.

I'd love to run a shroud, but that makes fans melt.

mad_machine wrote: sounds like you need two fans, Slant.. or a pusher in front of the radiator

Actually that was a question i should have asked in the first post as well:

I know we're all told that "pullers" are better than "pushers," but how much worse is a "pusher" setup, really? I can do pullers on the car in question, was just curious for future reference.

You can see Spal's numbers on their data sheets for puller vs pusher. Here's a randomly chosen one. Note that even in free air, it's more efficient as a puller - but as the static pressure climbs, the pusher starts to fall off faster.

https://webstore.spalusa.com/content/files/content/PDF/30102029_2030_2043_2132_SPEC.pdf

Keith Tanner wrote: You can see Spal's numbers on their data sheets for puller vs pusher. Here's a randomly chosen one. Note that even in free air, it's more efficient as a puller - but as the static pressure climbs, the pusher starts to fall off faster. https://webstore.spalusa.com/content/files/content/PDF/30102029_2030_2043_2132_SPEC.pdf

Weird... actually seems that the middle half of that chart seems to favor the pusher.

Wonder what the explanation for that is...

mad_machine wrote: sounds like you need two fans, Slant.. or a pusher in front of the radiator

When I went to electric fans, I had one of each! Offset, of course, with the pusher running with the AC and the puller on a temperature switch. There isn't much room in front of the radiator and condenser, either.

It seems the radiator was just not adequate for that car/engine/transmission/AC combination.

Now I'm working out how to have two thin pullers on the bigger aluminum radiator..

A shroud would be good if it improves flow, as most do. But if the shroud is too shallow, it may hurt more than help.

Swank Force One wrote:

Keith Tanner wrote: You can see Spal's numbers on their data sheets for puller vs pusher. Here's a randomly chosen one. Note that even in free air, it's more efficient as a puller - but as the static pressure climbs, the pusher starts to fall off faster. https://webstore.spalusa.com/content/files/content/PDF/30102029_2030_2043_2132_SPEC.pdf

Weird... actually seems that the middle half of that chart seems to favor the pusher. Wonder what the explanation for that is...

Duh, you're right. That IS interesting.

Keith Tanner wrote:

Swank Force One wrote:

Keith Tanner wrote: You can see Spal's numbers on their data sheets for puller vs pusher. Here's a randomly chosen one. Note that even in free air, it's more efficient as a puller - but as the static pressure climbs, the pusher starts to fall off faster. https://webstore.spalusa.com/content/files/content/PDF/30102029_2030_2043_2132_SPEC.pdf

Weird... actually seems that the middle half of that chart seems to favor the pusher. Wonder what the explanation for that is...

Duh, you're right. That IS interesting.

I'm actually intrigued enough i may try going to a pusher setup on my car, would make it easier to get effective ducting, since i can't run an effective shroud in a puller setup. And if i used strong enough fans, could help IATs as well, pulling hard through the intercooler.

The only thing that worries me is that on my car, i don't really have cooling problems except at very low speeds/stopped in traffic.

Talking about MX6, btw... The MSM has been great since you guys saved my hide. I need to get an undertray on it, though. It's cycling like crazy on the highway.

Why, um, you say that shrouds melt fans?

pres589 wrote: Why, um, you say that shrouds melt fans?

A proper shroud would space the fans a distance away from the radiator.

Which then would hit the turbo. Or at least come close enough that heat becomes a big problem.

Of course, there's a solution for that which involves a custom radiator setup, which really isn't a big deal, but doesn't fit in the Challenge budget. Cooling is adequate as it is, especially on mndsm's 88, which seems to be one of the overcooling freak examples, and on my car, it's just BARELY not keeping up while stopped in traffic. I'm reasonably sure i can fix my issues with some basic optimizations, and Tom's car remains not an issue.

You could do something like this;

http://www.carcraft.com/howto/ccrp_0707_high_performance_cooling_system/photo_16.html

pres589 wrote: You could do something like this; http://www.carcraft.com/howto/ccrp_0707_high_performance_cooling_system/photo_16.html

Unless i'm missing something, that shroud looks way too close to the core.

Neat article though! Bookmarked!

Honestly, though... these cars cool just fine with the stock radiator and whatever fans i happen to have laying around with the kind of turbo setups i run on them. Mine is the only one i've seen so far have problems with heat. It may very well have an old worn out water pump.

slantvaliant wrote:

mad_machine wrote: sounds like you need two fans, Slant.. or a pusher in front of the radiator

When I went to electric fans, I had one of each! Offset, of course, with the pusher running with the AC and the puller on a temperature switch. There isn't much room in front of the radiator and condenser, either. It seems the radiator was just not adequate for that car/engine/transmission/AC combination. Now I'm working out how to have two thin pullers on the bigger aluminum radiator.. A shroud would be good if it improves flow, as most do. But if the shroud is too shallow, it may hurt more than help.

have you considered what VW did? They had slots in their shourds on the A1 Rabbit.. with rubber flaps. When air was flowing through the radiator from speed, the flaps were pushed open.. when it was sitting and the fan was running, it pulled air from infront of the radiator

I made my own shroud out of sheet metal for the RX7 with a big 15" 2,300 cfm fan from Jegs. Keeps it idling all day at 180 degrees with two people autocrossing it in 100 degree temps.

I may engineer some way to run a shroud in the future, but it's going to require a smaller radiator. (Lengh/width wise, at least) Would have to mount it IN the core support, or more likely in front of the core support, sandwiched between the intercooler and the front of the support. Then i could probably even just weld a piece of sheet metal inside the support and cut holes and mount the fans to it.

But again... that's kinda something that may not be Challenge budget friendly. If i'm going to go through that trouble, it's not gonna be to use a cheap junkyard radiator and Ebay fans.

mad_machine wrote:

slantvaliant wrote:

mad_machine wrote: sounds like you need two fans, Slant.. or a pusher in front of the radiator

When I went to electric fans, I had one of each! Offset, of course, with the pusher running with the AC and the puller on a temperature switch. There isn't much room in front of the radiator and condenser, either. It seems the radiator was just not adequate for that car/engine/transmission/AC combination. Now I'm working out how to have two thin pullers on the bigger aluminum radiator.. A shroud would be good if it improves flow, as most do. But if the shroud is too shallow, it may hurt more than help.

have you considered what VW did? They had slots in their shourds on the A1 Rabbit.. with rubber flaps. When air was flowing through the radiator from speed, the flaps were pushed open.. when it was sitting and the fan was running, it pulled air from infront of the radiator

We do that on our production shrouds. SPAL part number 30130012 for the flaps.

Swank Force One wrote: If running with no shroud of any kind, just mounting slim fans on your radiator, do you want to size your fans to try to cover as much as the radiator as you can? Or does that end up impeding airflow too much while the fans aren't running? Radiator core is 15.75" x 25.5" Do i want two 12" fans, or two 10" fans?

You want these:

http://www.ebay.com/itm/Radiator-A-C-Fan-Replacement-98-00-Concorde-99-02-300M-99-01-LHS-98-02-Intrepid-/400311810687?pt=Motors_Car_Truck_Parts_Accessories&fits=Make%3AChrysler|Model%3A300M&hash=item5d34717a7f&vxp=mtr

except you want ones from a junkyard since these cheapy aftermarket ones don't look like the fans themselves are any good.

These move a lot of air. A LOT of air. Each fan has low and high. Even if you only wire them in on "low" they will probably be good enough, and if you need more you can add another couple relays to get high. Gauging from experience with previous fans, low is about 2500cfm and high is maybe 4000, as a SWAG.

I cut the ears off and riveted a couple pieces of aluminum flat stock for mounting to my radiator.

I will keep that in mind when I ditch the mechanical fan off of the rover

In reply to Knurled:

Definitely won't fit without some pretty extensive modification to the car, something I don't want to get into right now.

I have some very slim slim fans mounted to a stock (probably slightly slimmer than stock, actually) radiator that has been moved forward a half inch.

I have an inch at most between turbo and fan, which forces me to have to use a turbo blanket so the fans don't melt.

it doesn't take a lot of radiator or a lot of fan to keep an engine cool- i kept the vortec headed 355 in my Nova that was somewhere around 400 magazine HP right at the 195 thermostat temp with a crusty old radiator for a 6 cylinder car and an electric fan out of an 86 Celebrity with a 4 cylinder and no other shrouding at all... the only time it got hotter than 200 was when i'd hit the interstate and crank it at 3500+ rpm for an hour and a half at a time, and then it only got up to 205, which was probably from crappy aero that a chin spoiler probably would have solved..

the stock wimpy 305 in my current 86 Camaro is kept cool by the stock V6 electric fan, but with a brand new V8 radiator- it goes up to the 220 degree fan activation temp, then goes almost immediately down to the 215 degree fan "off" temp..

those shrouds that cover the whole care are a bad idea with an electric fan unless you want the fan to run all the time for some reason... you can put trap doors that open up and let air flow thru the core when the vehicle is moving to actually use more of the core to keep the car cool..

Sooo... what you're saying is that i should give the Civic half width 3 row radiator a shot with a single obnoxiously strong fan?

I have one of those civic radiators. I can sell it to you for challenge money.