scudderfish
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| posted on 26/3/15 at 07:17 PM |
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Suck or blow?
Is there any difference between putting the rad fan on the front and blowing through, or on the back sucking?
Regards,
Dave
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nickm
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| posted on 26/3/15 at 07:33 PM |
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Hi
Think most will say behind and suck is more efficient, as the fan itself doesnt disrupt the air flow.
Nick M
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Acc8braman
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| posted on 26/3/15 at 07:50 PM |
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Mine are suckers 
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Badger_McLetcher
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| posted on 26/3/15 at 08:09 PM |
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I can't remember where, but I seem to have the figure of suck throughs being about 20% more efficient in my mind. It makes sense, as Nick said
they don't disrupt the airflow that way and so you have more lamina flow over the fins.
If disfunction is a function, then I must be some kind of genius.
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SPYDER
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| posted on 26/3/15 at 09:51 PM |
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The front mounted "blowing" fan is operating in cooler, therefore denser air than the rear mounted "sucker".
Shouldn't that increase its efficiency?
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slingshot2000
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| posted on 26/3/15 at 10:58 PM |
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I cannot find it, but a long, long, long time ago I used to wear a T-shirt with a picture of a big, supercharged, American V8 on the front.
Below the picture the legend read;-
"I'd rather be blown , than injected !
[Edited on 26/3/15 by slingshot2000]
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Badger_McLetcher
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| posted on 26/3/15 at 10:59 PM |
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The fan causes a hell of a lot of turbulence and generally messes up the airflow, which reduces heat transfer from the radiator (you want a nice
smooth flow). If you suck in the air it remains smooth until it hits the fan - that's also why wind tunnels suck through rather than blow
through.
There may be another mechanic at play here, but that's what I can remember
If disfunction is a function, then I must be some kind of genius.
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Badger_McLetcher
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| posted on 26/3/15 at 11:00 PM |
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Also the density of the air doesn't overly affect flow through the fan - I'd imagine the change in density is relatively small compared to
the flow through the fans.
If disfunction is a function, then I must be some kind of genius.
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coyoteboy
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| posted on 27/3/15 at 01:06 PM |
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Best option for this situation is rear-mounted with a cowl around the fan and the blades a small distance from the rad surface.
Too close and you get a lot of "chopping" noise.
Too far and you suck air in around the fan not through the rad.
Cowl increases fan efficiency by a LONG way.
That said, front mount might affect efficiency but the bulk of your rad surface will be free of fan effect and when you're moving >50mph the
airflow from the car will out-perform the fan anyway.
If you can't fit a cowl to guide air into the fan, put the rad in front.
[Edited on 27/3/15 by coyoteboy]
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steve m
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| posted on 27/3/15 at 04:55 PM |
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Mine is behind the rad, and for the only reason is that I believe it looks neater looking through the grill at the rad
plus in theory the airflow is constantly on the front rad surface while moving and not restricted in any way
also the fan should not really be coming on in normal instances
Thats was probably spelt wrong, or had some grammer, that the "grammer police have to have a moan at
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DJT
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| posted on 27/3/15 at 07:43 PM |
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Ive got a new Revotec 12" slimline sucker going cheap if interested.
http://tigeravonbuilddiary.blogspot.com/
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simonrh
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| posted on 27/3/15 at 08:39 PM |
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One of things I did to cure my overheating was convert to rear mounted fan
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