locost7-online.com
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| posted on 12/1/16 at 09:48 PM |
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Electric cooling fan
What's good to use as cooling fan for polo radiator with 900 blade engine? Push pull? Size price etc
Locost Xflow 150bhp injected! Sold :-(
Facebook blog https://www.facebook.com/Johns-Tiger-Avon-Build-814223212056368/
PLEASE NOTE THIS MEMBER IS NOT A TRADER.
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CosKev3
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| posted on 12/1/16 at 10:06 PM |
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Spal are one of the best brands,JJC Race and Rally had some good prices on them when I bought one not long ago.
Go for the biggest you can fit in.
Pull fan is the most efficient iirc 
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locost7-online.com
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| posted on 12/1/16 at 10:18 PM |
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I was swaying towards pull fan, looks neater too
Locost Xflow 150bhp injected! Sold :-(
Facebook blog https://www.facebook.com/Johns-Tiger-Avon-Build-814223212056368/
PLEASE NOTE THIS MEMBER IS NOT A TRADER.
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02GF74
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| posted on 12/1/16 at 11:10 PM |
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Hmmm i thought push was more efficient.
Fit largest you can get and have a cowl so air has no path other than via radiator.
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loggyboy
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| posted on 12/1/16 at 11:24 PM |
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I assumed pull as less blocking air coming in to rad. You want rad to be most efficient when in normal use, Fan is only used when warm and still,
which is more common for daily drivers than track and weekend cars.
Mistral Motorsport
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cliftyhanger
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| posted on 13/1/16 at 07:51 AM |
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How much space behind the rad?
In my car I fitted a polo/golf fan complete with cowl. It is amazing, the cowl makes the fan MUCH more efficient, plus will mount easily to teh
orignal lugs on teh rad rather than through the core (which always worries me, but never actually had a problem!)
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craig1410
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| posted on 13/1/16 at 10:49 PM |
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I would expect a pull fan to be most efficient as you can more easily install it in a cowling. I don't think I've ever seen a push fan in
a cowling but I could be wrong.
I've actually got a polo cowling for my polo radiator but I replaced it with a modern fan as large as the core height would allow. The old fan
had only 3 or 4 blades as I recall and was far less sophisticated in terms of blade design. My modern fan has loads of blades and they look much more
efficient. I suspect that any deficit from not having a cowling will be made up but the sheer size and ability to move air of the modern fan.
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nick205
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| posted on 14/1/16 at 10:27 AM |
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From memory I fitted a SPAL pull fan to my Polo rad in my MK Indy 2.0 Pinto - never had any cooling issues with it.
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Badger_McLetcher
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| posted on 14/1/16 at 05:46 PM |
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I thought pull fans were meant to be up to 20% more efficient as they give a lamina flow over the rad without the turbulence caused by the fan
itself.
[Edited on 14/1/16 by Badger_McLetcher]
If disfunction is a function, then I must be some kind of genius.
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coyoteboy
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| posted on 14/1/16 at 08:58 PM |
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The last thing you want is laminar flow over a rad. By definition if you have laminar flow you have a boundary condition that separates the main flow
from the surface and reduces heat transfer. Turbulent flow is orders of magnitude better for heat transfer.
They're a lot quieter which is part of the reason a lot of OEMs use it.
You can test it yourself - wet your face, stick it on the pull side of a desk fan and feel the cooling effect, then stick it the same distance away on
the push side and see which feels cooler.
[Edited on 14/1/16 by coyoteboy]
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Adamirish
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| posted on 14/1/16 at 10:23 PM |
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What ever you do, don't buy cheap. I skimped and bought one off eBay for £25. All the specs were very similar to the equivalent spal. Needless
to say, it was shite!
Got a proper spal pull fan and the difference is night and day. Nearly 4 times the price but worth every penny. Buy cheap, buy twice. Like me!
MK Indy 1700 Xflow
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colin99999
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| posted on 15/1/16 at 05:46 PM |
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I'll second the above. My car came with a cheapo reversible blade fan ready to fit but it could barely suck a waft of smoke through my 50mm
thick rad. Luckily I happened across a new but used Spal just the right size on Gumtree & as mentioned above the difference is night & day!
Most folks are about as happy as they make up their minds to be...
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Badger_McLetcher
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| posted on 15/1/16 at 09:46 PM |
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quote:
Originally posted by coyoteboy
The last thing you want is laminar flow over a rad. By definition if you have laminar flow you have a boundary condition that separates the main flow
from the surface and reduces heat transfer. Turbulent flow is orders of magnitude better for heat transfer.
They're a lot quieter which is part of the reason a lot of OEMs use it.
You can test it yourself - wet your face, stick it on the pull side of a desk fan and feel the cooling effect, then stick it the same distance away on
the push side and see which feels cooler.
[Edited on 14/1/16 by coyoteboy]
Hah yeah you are right - boundary layer formation is not a good thing for heat transfer, I was still in wind tunnel/wing mode... I digress. I would
still argue that a puller system is better for a radiator due to less obstruction of the frontal area on the move. Ducting is a big help as well
mind.
The 20% figure I've seen bandied around a lot, but now I'm wondering where it came from. It would make an interesting experiment.
If disfunction is a function, then I must be some kind of genius.
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craig1410
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| posted on 15/1/16 at 10:23 PM |
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I don't think there is any doubt that puller fans are more efficient is there? As far as I'm aware, the radiator core fins are rippled to
increase the scrubbing effect of the air and remove any boundary layers.
As for ducting, technically it reduces overall cooling due to aerodynamic obstruction, but since most overheating occurs at idle in a stationary
vehicle, ducting can help by allowing the fan to act over a greater core area.
What is equally important as ducting is ensuring that all the air which enters the nosecone is forced through the core so try to seal between nosecone
and radiator as much as possible. A combination of aluminium sheet cut to the inside profile of the nosecone plus large diameter rubber hose for
padding can be useful here.
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02GF74
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| posted on 15/1/16 at 10:33 PM |
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quote:
Originally posted by craig1410
I don't think there is any doubt that puller fans are more efficient is there?.
Is there?
Googling indicates slightly more people say pull are better but ni back up other than hearsay.
Im sticking with push. A puller can only suck one atmosphere at most but pusher can do more if necessary.
Also one revoution of the fan, the volume wil be the same but less air molecules are shifted by a puller as the air had expanded due being heated by
the radiator.
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craig1410
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| posted on 15/1/16 at 11:06 PM |
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Hmm, I think maybe your logic is flawed.
When you compress air it heats up. So, if you compress the air *before* the radiator it will be hotter than ambient from a combination of the
compression and the heat from the fan motor. On the other hand, with a puller fan, the air within the core will be at a slightly power pressure than
ambient which will reduce the air temperature.
I've not gone to the trouble of doing the maths but I would expect this effect will at least counteract the density difference you were talking
about and might even be beneficial overall.
That all said, this only really covers static cooling (ie. when stationary) not when running at cruising or racing speeds where the fan isn't
spinning and is instead causing an obstruction along with the cowling. That's why I don't use a cowling. My radiator is probably twice the
capacity I need at idle so my fan only needs to act on half of it. Then at speed I get airflow through the whole radiator without restriction which
gives me the cooling I need for full power or fast cruise.
I would be very interested to see any hard data on puller vs pusher if anyone has it. I'd be very surprised if pusher was better though just
from an intuition.
Edit: Here's the "TEN COMMANDMENTS FOR MAXIMUM COOLING" from a cooling specialist. http://www.griffinrad.com/tips.cfm
"...Preference should be given to a "pull" vs. a "push" fan. Mounted on the engine side of the radiator, a pull fan does
not interfere with air flow at highway speeds. All shrouded fans should be on the engine side of the radiator. "
[Edited on 15/1/2016 by craig1410]
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02GF74
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| posted on 15/1/16 at 11:28 PM |
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I can bet that the temp increase due to the pusher fan is significantly less that that when air has passed through radiator, i.e. the puller case.
Also remember the puller motor sits in hot air, the windings are metal which increase in resistance with temperature, so less power is going to it so
it will shift less air than pusher. I need to do some calcs but dont expect it to be significant but still is 1 point for the pusher.
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CosKev3
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| posted on 15/1/16 at 11:33 PM |
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Spal state a puller fan is more efficient,that's good enough for me
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02GF74
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| posted on 15/1/16 at 11:35 PM |
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quote:
Originally posted by craig1410
"...Preference should be given to a "pull" vs. a "push" fan. Mounted on the engine side of the radiator, a pull fan does
not interfere with air flow at highway speeds. All shrouded fans should be on the engine side of the radiator. "
Agreed. Fan is not needed when vehicle is moving.
Air flow through engine will hit the fan whether it is in front or behind the radiator, question is whjch positon cause less interference, with or
without a shroud.
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craig1410
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| posted on 15/1/16 at 11:36 PM |
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quote:
Originally posted by CosKev3
Spal state a puller fan is more efficient,that's good enough for me
So that's 2 cooling specialists recommending puller fans. This reminds me of watching the football scores come in.
.....City 2.........United nil.....
.....Puller 2..........Pusher nil.....
edit: Link here: https://www.a1electric.com/spal/faninfo.htm
"Fans work the best when used in the "pull" configuration. In other words the fan should be mounted on the backside of the radiator
facing the engine."
[Edited on 15/1/2016 by craig1410]
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Adamirish
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| posted on 15/1/16 at 11:38 PM |
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So. Ah. Which fan is good for the op?
MK Indy 1700 Xflow
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craig1410
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| posted on 15/1/16 at 11:49 PM |
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quote:
Originally posted by Adamirish
So. Ah. Which fan is good for the op?
Well he did ask about push vs pull to be fair. 
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Adamirish
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| posted on 15/1/16 at 11:53 PM |
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quote:
Originally posted by craig1410
quote:
Originally posted by Adamirish
So. Ah. Which fan is good for the op?
Well he did ask about push vs pull to be fair.
Touchè
MK Indy 1700 Xflow
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slingshot2000
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| posted on 16/1/16 at 12:21 AM |
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quote:
.....City 2.........United nil.....
.....Puller 2..........Pusher nil.....
20,000 empty seats ?
You're having a laugh ????
[Edited on 16/1/16 by slingshot2000]
[Edited on 16/1/16 by slingshot2000]
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02GF74
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| posted on 16/1/16 at 01:00 AM |
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quote:
Originally posted by craig1410
quote:
Originally posted by CosKev3
Spal state a puller fan is more efficient,that's good enough for me
So that's 2 cooling specialists recommending puller fans.
One of your "experts" says fan behind radiator does not interfere with air flow, ofcourse it does, air cannot flow through a solid object.
A so called expert recommending push.
https://www.highpowermedia.com/blog/3821/radiator-fan-installation
There is test data albeit for cpu fans showing push is better than pull without cowling
The import part is that it is the cowling that makes the biggest difference.
Im not convinced pulk is more efficient until ive seen data. :p
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