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alum rad fans. pusher vs puller

 
Old 05-03-2019, 03:55 PM
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ronarndt
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Default alum rad fans. pusher vs puller

I have a four tube aluminum radiator in my 68 convert with NOM 454. The belt-driven stock fan has been removed. The electric fan was mounted on the front side of the radiator as a pusher fan by the PO. I have a temperature relay that starts the fan at 180 degrees. Most applications use the fan as a puller and mount it on the engine side of the radiator. Does anyone have data using the same radiator and fan to show if there is a difference in coolant temperature with the fan mounted as a pusher vs mounting it as a puller? My car does not overheat, but when sitting in traffic, the temp goes up from the normal 180 (at highway speeds) to about 210 {sitting in traffic on a hot (80 degree or hotter) day}. If a puller fan would lower the sitting-in-traffic temp significantly, I would move the fan. If not- it stays where it is. I expect many will want to pipe in with their opinions, but I would appreciate any who have actually used the same radiator and fan with the fan mounted in the two different configurations. TIA
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Old 05-03-2019, 04:12 PM
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derekderek
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Fan blades are curved. They have a lead and trail edge. Yes if you hook it up backwards it will push air in the other direction. Not nearly as well as a fan made to move air that way. So you would really need a different fan, at least the blade, to move air the other way.
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Old 05-03-2019, 04:16 PM
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Originally Posted by derekderek View Post
Fan blades are curved. They have a lead and trail edge. Yes if you hook it up backwards it will push air in the other direction. Not nearly as well as a fan made to move air that way. So you would really need a different fan, at least the blade, to move air the other way.
^ this. If the fan was configured as a push type, it should do its job as well as a pull type.
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Old 05-03-2019, 04:21 PM
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If it doesnt overheat why make changes..now if it is coming on at 180 and still gets to 210 does it want to creep higher?
With a 4 row imo you need a more powerful setup so its not working that hard all the time.

If you have a little budget look up DeltaPaq brusheless, nice stuff and "smart".

Looked at a 1 yr old Corolla (Rental car), FIL F150 they both use brushless fans with the same controller. THey sit dead nuts stable on temps all day no matter what the condition.
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Old 05-03-2019, 05:21 PM
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Originally Posted by PainfullySlow View Post
^ this. If the fan was configured as a push type, it should do its job as well as a pull type.
The blade can be taken off the hub and reversed to keep the directionality the same and the motor can be reversed to make sure the blade turns the correct direction after flipping it. But.....I don't want to go thru all this if it won't make a difference in the coolant temp.
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Old 05-03-2019, 05:41 PM
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I was hoping you would move it from front to back and give us all a data driven result, like you I've read the puller is a better position and several guys on the HAMB board claim to have seen the improvement but I haven't seen any examples of the gain.
I recently switched to an alum rad and single puller on my 460 68 vert, like you the PO had the factory fan clutch unit w orig rad/shroud and a twin pusher on the 427 and it always hit 210 even with the twins turned on on a hot day.

I haven't had the new combo out on a hot day yet but it held around 180 moving or still last year (I think mid 70's was the highest it's seen so far) due to late start driving it.
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Old 05-03-2019, 06:01 PM
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L-46man
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Quick Radiator Aerodynamics...

PUSHER fans BLOCK the airflow across the radiator by the cross-sectional area of the Fan motor/ Armature/ strakes/ and mounting frame.

IF one was to mount the fan on the 'PULLER' side....ALL the air goes thru the matrix of the radiator...INCLUDING when the fan is not running.
Puller fans (like God, Chevy and Zora intended) ALSO create a 'partial vacuum' (delta P) around the FAN SHROUD ANNULUS... (circumference) when proper airflow technique is used...such as carefully foaming ALL the gap-age between radiator, Core support and Fan Shroud and under hood area...(SORRY FOR THE CAPS! LOL) THE AIR HAS NO CHOICE BUT TO GO THROUGH THE MATRIX OF THE RADIATOR.

The Original owner took a BAD short-cut.

The 82 CE has TWO fans, the tried and true 5 blade metal fan with fan clutch AND a PULLER fan behind the radiator...I'm in AZ.... My car runs at 165 at 100 F ambient and a 160F thermostat....no cooling issues what-so-ever.
On the 69 I have a 7 blade big-block fan and a stage 3 fan clutch...(the most aggressive)...that puppy runs cool as a jewel too.

Electric fans are great for HP....cooling must be done PROPERLY with them however.

Derek Derek also has a great point...they're not PADDLES!

Thanks for asking!

UNKAHAL
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Old 05-04-2019, 10:21 AM
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When used as a pusher fan, all of the airflow thru the rad at idle is only what the fan is pushing. A round fan may cover what, about 70% of the rad face?
Put that same round fan on as a puller and you cover the same amount of rad and pull the same air thru the same amount of rad at idle. Not much will change.
Add a shroud with the puller fan and now you can pull air thru 100% of the rad face at idle and you should see an improvement.
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Old 05-04-2019, 10:28 AM
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ajrothm
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Pusher fans never work good, all they do is block flow from the front of the radiator. Move the second fan to the engine side of the radiator if you have room for it, it will cool much better at idle and on the highway.
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Old 05-04-2019, 12:50 PM
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in addition to the good info re: curved fan, use a puller etc ...also ensure you have OE chin spoiler (or similar) installed on your bottom-breather ...
... makes little difference in slow traffic but sure does when faster

Also ... some folk have had good results retrofitting OE puller fan & OE shroud from Lincoln Mark VIII and similar... see this thread
https://www.corvetteforum.com/forums...-viii-fan.html

FYI ... fwd Mark VIII has a hi-output 4.6L V8 mounted transverse ... '98 -2011 rwd Towncars have a similar engine & fan setup and I can verify (owned 3) how robust & effective the OE stuff is. Knock wood; one is current DD. Just a fancy crown vic.
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Old 05-05-2019, 09:23 PM
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I can't find the test-

BUT the pusher was MORE efficient minimally - however it used more current electrically.

As others have said- it blocks flow running down the road.

The puller is the best compromise as it takes less current and not block the radiator when not in use.

The best is to have the puller shroud with flaps that open at speed-

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Old 05-05-2019, 09:29 PM
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Richard what setup is that? Thanks
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Old 05-05-2019, 09:52 PM
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Originally Posted by cuisinartvette View Post
Richard what setup is that? Thanks

C7 upgrade fan-
  • Part Number: 23376530

https://www.gmpartsdirect.com/oem-pa...r-fan-23376530
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Old 05-06-2019, 09:52 AM
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cuisinartvette
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Interesting, does it need a controller of some type?Cfm rating (Sure its sufficient!)
For the money sounds good...plus oem reliability. Curious to its measurements width x length
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Old 05-07-2019, 06:19 AM
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terrys6t8roadster
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There is a CFM rating on electric fans. In the puller position the rating is higher than the pusher. T
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Old 05-07-2019, 06:28 PM
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Originally Posted by c69vete View Post
When used as a pusher fan, all of the airflow thru the rad at idle is only what the fan is pushing. A round fan may cover what, about 70% of the rad face?
Put that same round fan on as a puller and you cover the same amount of rad and pull the same air thru the same amount of rad at idle. Not much will change.
Add a shroud with the puller fan and now you can pull air thru 100% of the rad face at idle and you should see an improvement.
THIS! Puller fan with shroud pulls air across the whole surface of the radiator. Pusher fan only pushes air across the surface area of the radiator covered by the fan.

At high speeds with airflow directed up through the radiator might not be a big deal, but around town, pull fan + Shroud ==more better.

Adam
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Old 05-07-2019, 06:32 PM
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Originally Posted by Richard454 View Post
The best is to have the puller shroud with flaps that open at speed-
Agree 100%!
For anyone looking for a NEW radiator you can order the Champion radiators with your choice of single or dual fans (upgradeable to Spal fans) AND you can add the option for flaps for highway speeds.

I didn't go with the flaps, but I reserve the right to add them in the future.


Adam
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Old 05-08-2019, 06:35 PM
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Unless it starts really heating up at idle you can probably do without the shroud.
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