ken555
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| posted on 15/5/10 at 04:31 PM |
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Fan Shrouds
Just how much a difference do they make ?
I'm fitting twin fans, on a two stage switch.
Would shrouding them in make much of a difference, or is it OK just to have them like this ?
Without.
Idea
[Edited on 15-5-10 by ken555]
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02GF74
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| posted on 15/5/10 at 05:06 PM |
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yes it will make a difference; cannot give you any figures.
the fan will blow/suck air through the part of thje radiator that is equal to its are but with a shroud, that can be increased substantially - will
help lots when stationary.
you will find production cars have shrouds and it stands to reason they would not go to that trouble and cost if there was no point.
cannot see what is happening in second picture but in effect you need to construct a pyramid, then chop the top off parallel to the base and fit a
cover with hole for the fan.
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hillbillyracer
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| posted on 15/5/10 at 10:28 PM |
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Are they just for cooling while the car is stationary or does it not get enough air when moving?
If it's just when sitting idling etc then I think they'll be fine as the engine won't be making much heat then anyway. Looking at
your first pic the fans touch the top edge of the rad, do they touch the bottom edge too? That would mean all of the cooling tubes of the rad cross
the fan at some point so all of them would at least get some benifit from the fan's airflow.
I ran a rear mounted rad on my front engined grasser, it was a 2l Sierra rad with 2 fans from a Nissan Sunny mounted side by side like yours but with
the shrouds from the Sunny too. As luck would have it the two shrouds side by side were a perfect fit for the Sierra rad. If I forgot to switch the
fans on it'd be cooking in 2-3 laps but with them it never got hot & this was a 2l 8v turbo & later a 2l 16v N/A working hard not
sitting idling in traffic.
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ken555
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| posted on 15/5/10 at 10:47 PM |
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quote:
Originally posted by hillbillyracer
Are they just for cooling while the car is stationary or does it not get enough air when moving?
Just for stationary.
If anything the radiator overcools the car when moving.
This was the previous set-up and never had a problem with it.
[Edited on 15-5-10 by ken555]
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RazMan
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| posted on 15/5/10 at 11:13 PM |
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In my experience shrouding is most effective in front of the radiator, directing the air through to a 'puller' fan which kicks in while in
slow traffic.
Your top picture would be the best solution IMO, without any shrouding blocking the airflow like the bottom picture - that will just build up pressure
in front of the fans and prevent natural airflow.
[Edited on 15-5-10 by RazMan]
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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hicost blade
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| posted on 15/5/10 at 11:38 PM |
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Over cooling is a lot easier to adjust than over heating
First of all the fans should only work when stationary
Shrouds are only useful when the fans are working and are used in production cars to get the most from cheap inefficient fans
Your car cools perfectly well with the 1 'scrap yard' fan
You want the maximum air flow when under load as in when being driven, a rear 'fan shroud’ can only inhibit air flow.....
In short forget a fan shroud, if anything I would duct the air into the radiator from the inlet from the front of car like most 'race
cars' employ
If it over cools use card to block off part of the radiator cores on cool days and if it gets warmer remove the card or alter it to suit the
conditions
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02GF74
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| posted on 16/5/10 at 05:58 AM |
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quote:
Originally posted by ken555
quote:
Originally posted by hillbillyracer
Are they just for cooling while the car is stationary or does it not get enough air when moving?
Just for stationary.
If anything the radiator overcools the car when moving.
This was the previous set-up and never had a problem with it.
ah, you didn't say that or post the photo .... a quick glance shos the area swept by the fan blades is comarable if not slight bigger than the
single fan so you should be ok.
note shroud will improve colling when fans are running = stationary and will restrict air flow more than if they were not there so may have the
overcolling issue when air is beiong force through the radiator = driving.
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ken555
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| posted on 16/5/10 at 08:19 AM |
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quote:
Originally posted by 02GF74
ah, you didn't say that or post the photo .... a quick glance shos the area swept by the fan blades is comarable if not slight bigger than the
single fan so you should be ok.
If My Maths serves me right the ratio is 50 to 36. (2x10" to 12" ) so a 1.4 times improvement.
Thanks all.
[Edited on 16-5-10 by ken555]
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02GF74
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| posted on 16/5/10 at 09:29 AM |
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quote:
Originally posted by ken555
If My Maths serves me right the ratio is 50 to 36. (2x10" to 12" ) so a 1.4 times improvement.
I think you'll find is less than that as you have not taking into account the dead space in the centre.
you need to measure the area swept by the blades - the central portion does not contribute to air flow.
then there is rpm plus fan blade depth and shape.
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