Go for the biggest you can fit in.
Pull fan is the most efficient iirc
What's good to use as cooling fan for polo radiator with 900 blade engine? Push pull? Size price etc
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
I was swaying towards pull fan, looks neater too
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.
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.
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!)
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.
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.
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]
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]
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!
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!
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]
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.
quote:
Originally posted by craig1410
I don't think there is any doubt that puller fans are more efficient is there?.
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]
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.
Spal state a puller fan is more efficient,that's good enough for me
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. "
quote:
Originally posted by CosKev3
Spal state a puller fan is more efficient,that's good enough for me
So. Ah. Which fan is good for the op?
quote:
Originally posted by Adamirish
So. Ah. Which fan is good for the op?
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.
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]
02GF74 - 16/1/16 at 01:00 AMquote:
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
craig1410 - 16/1/16 at 01:17 AMI've yet to see a CPU fan attached to the front of a car doing xxx MPH so I think I'll settle for the opinion of the two specialists mentioned above as well as my own intuition until data to the contrary comes to light.
02GF74 - 16/1/16 at 01:52 AMOne of your specialist made an incorrect statement so what else has he got wrong? Is he quoting the same stuff everyone else is quoting with no data to back it up?
Look at spal fan data. The flow and current for straight blade fans of same diameter is the same for pull and push.
Note curved blade pull fan gives better flow for same current and size to the above.
Therefore i reject the statement that pull is better than pull since there is no indication it is comparing like with like, in fact the data implies there is no difference unless a fan with optimised blades is used, which i suspect spal refer to.
You dont like my cpu data as it is against what you believe but is it a matter of scale or are the other factors involved that make the data not appliicable to this discussion? I dont know and until i see data im sticking with push for reasons given earlier and the physics backs me up.
02GF74 - 16/1/16 at 02:06 AMquote:
Originally posted by craig1410
I've yet to see a CPU fan attached to the front of a car doing xxx MPH
But you must have, the car fan is a cpu fan but bigger and im not discussing efficiency when car is moving because if the radiator is correctly sized, the fan plays no part. People on here have used cpu fans for oil coolers.... but is data for a small fan applicable when scaled up? I expect the airflow to be different but weve all seen scale models in wind tunnels so the airflow cant be all that different.
I'm not having a go at anyone or want to argue, but simply don't accept random quotes from "experts" that defy the laws of physics.
Here are those laws:
1. When a gas is compressed, its pressure increases.
2. For a gas to flow there must be a pressure difference.
3. A car radiator, despite its name, transfers heat by convection.
4. The amount of heat transafered out of a radiator increases as the amount of air flowing though it increases.
5. A puller fan, cannot pull more than 1 atm of air whereas a pusher fan can. In other words, the pressure of air flowing through the radiator is less for a puller than a pusher.
6. When a gas is compressed, e.g. air its pressure increases.
So for a pusher and puller fan of the same flow in free air, when presented with a resistence to flow e.g. a radiator,
the air flowing through the radiator will be at a higher pressure for a pusher see 1. 2. 5.
The higher pressure means there is more air going through the radiator, so more heat is transferred see 3. 4. so it is more efficient.
As pointed out the air will be at a higher temperature but that does not affect the overall result.
You experience this when driving.
If the car is idling when stationary, the temperature rises as there is no air flow
through the radiator.
When moving at a snail pace, the temperature will rise but not as fast.
When moving at speed, the temperature is constant due to the thermostat. That is because more air is being pushed through the radiator even though it may get slightly hotter due to being compressed.
So to conclude, more heat is moved from the radiator as more air flows through it and it is a pusher fan that can flow more air than a puller hence is more efficient.
Anyways, im leaving it at that as without any test data neither of us are going to agree.
[Edited on 16/1/16 by 02GF74]
gregs - 16/1/16 at 08:30 AMFWIW - don't exclude a raid to the breakers.... I've got a Proton pull fan on mine (on a civic VTEC rad!) mounted direct to the rad. It's not the slimest (prob about 75mm) but comes with a free square cowl and flows a significant volume when it kicks in.. total investment for fan and rad... £15.
Greg
[Edited on 16/1/16 by gregs]
CosKev3 - 16/1/16 at 10:26 AMWhere's the yawning smiley
Dropped off nicely reading that.......
CosKev3 - 16/1/16 at 03:04 PMquote:
Originally posted by 02GF74
Look at spal fan data. The flow and current for straight blade fans of same diameter is the same for pull and push.
Yeah but surely that's just the fan running on its own during a test without being fitted to a radiator?
snowy2 - 16/1/16 at 03:39 PMone of the universities has done the research and there is no difference between push fan or pull fan. the shadow they cause is the same either side of the radiator.....go for what fits and dont worry about it.
snowy2 - 16/1/16 at 03:44 PMducting is very important....if the air can find a way round the radiator it will do......also a radiator stuck out in the air flow getting clean "Laminar" air will NOT cool as well as a Radiator getting turbulent air....weird but true.
craig1410 - 16/1/16 at 04:31 PMquote:
Originally posted by snowy2
one of the universities has done the research and there is no difference between push fan or pull fan. the shadow they cause is the same either side of the radiator.....go for what fits and dont worry about it.
It'd be very interesting to see that study if you know which university did it. Otherwise I'm afraid we're no farther forward in separating myth from reality.
I'll repeat what I said last night and recommend that everyone ensures they have more than enough cooling capacity and seal between nosecone and radiator to ensure the airflow can't bypass the radiator core. If you do that then you don't need to worry about any minor differences between push vs pull and can go with the one you find most convenient to install or aesthetically more pleasing.
If anyone is looking for donors at the scrapyard then you'll find puller fans much more common. Whether this is because car manufacturers believe this is more efficient or if they are also deluded I will leave up to the reader.
renetom - 16/1/16 at 05:03 PMHi
We used a polo rad & a polo fan which cost £6 on ebay
is reversible easy to mount & was perfect for our car
with yamaha R1.
good luck
René
02GF74 - 16/1/16 at 05:45 PMquote:
Originally posted by craig1410
If anyone is looking for donors at the scrapyard then you'll find puller fans much more common. Whether this is because car manufacturers believe this is more efficient or if they are also deluded I will leave up to the reader.
well didn't take for the insults to start but I'll ignore that.
The reason you find more puller fans fitted to cars is because the fan sits in a cowl. Cowling makes a huge difference and works better when the car is driven by being behind the radiator. I have never disputed any of that but will continue to disagree that a pull fan is more efficient better at removing heat than push fan. The example you cite above has nothing to do with efficiency of pull vs pull but efficiency of cowl siting.
I have listed the physics and my reasoning already, please tell me which part you don't agree with.
Lets make it really simple and say you have a fan that moves the same amount of air in both directions and mount it on the mouth of a sealed jar.
Wire it up so is acts as a puller so it sucks air out of the jar. The air inside the jar will be a less than 1 atmosphere.
Wire it up so it pushes air in and the pressure inside the jar will be above 1 atmosphere.
Now mount it to a radiator so the jar in effect is the radiator matrix, the pressure will follow the same pattern.
Higher pressure = more air molecules = more heat transfer; therefore pusher is more efficient (the effect of any change in temperature is minimal as the fans are not very good compressors). Show me at which point I am deluded.
In summary, if there is a cowl, the cowl and fan sit behind the radiator and fan is a puller.
If it is just a fan and it moves same amount of air in both directions, then it sits as close as possible and in front of the radiator.
This ofcourse assumes there is a choice where to mount the fan.
[Edited on 16/1/16 by 02GF74]
craig1410 - 16/1/16 at 06:03 PMJust to be clear, I was suggesting perhaps I am deluded along with the car manufacturers so no need to take offense!
To avoid CosKev3 nodding off I'll keep my response short. No jars required either...
You agree a puller in a cowling is best and we've already said a cowling is recommended so sounds like a puller in a cowling is best. Job done!
[Edited on 16/1/2016 by craig1410]
snowy2 - 16/1/16 at 06:08 PMbmw mercedes citroen use pusher fans ford vw audi use puller fans....it really doesn't make any difference....
craig1410 - 16/1/16 at 06:10 PMquote:
Originally posted by snowy2
bmw mercedes citroen use pusher fans ford vw audi use puller fans....it really doesn't make any difference....
Well my BMW E61 uses a puller. Can't comment on the others and wouldn't want to generalise.