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Thread: To shroud or not to shroud: pusher fans

  1. #1
    Problem? sssgtr's Avatar
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    To shroud or not to shroud: pusher fans

    Going to mount up the Spal 12" pusher fan I picked up this weekend, there isn't a whole lot of information about shrouding pusher fans.

    Since I'm only running the one fan (left half of the radiator), I want to know if it's worth fabricating a shround into the fan mounts to cover this half of the rad, and leave the other half without the fan as is (obviously!).

    I will be making up trim pieces to go around the whole radiator to ensure as much of the incoming air is being forced through the core, and once i have fabricated the manifold and mounted the turbo, to work out a method of ducting the right half (no fan side) of the radiator either out through the bonnet or underneath the car.

    It's not going to sit in traffic, so i'm not concerned about having to run 2 fans as one should keep it cool at idle and low speed. There is no AC condensor in the way either.

    I will be going to a thicker custom rad at some stage, but not just yet.

    To shroud or not to shroud?

  2. #2
    formerly shinybluesteel Roadsailing's Avatar
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    I wouldn't bother, if it overheats then you can shroud it. a while back i ran a single N14 pulsar fan on the front of my radiator running backwards and i never had any problems with that.

  3. #3
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    i thought the shrouding was more effective in a puller config, i.e. drawing the larger area of air through the smaller hole made it go faster? or something?
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  4. #4
    Non player character GTSBoy's Avatar
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    If you don't shroud a pusher fan then a good proportion of the air that comes off the blades will spill out the side without going through the core.

    Ultimately the situation between pushers and pullers is exactly the same. If you don't shroud a puller, then it will pull air from the sides rather than through the core.
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  5. #5
    Problem? sssgtr's Avatar
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    Good point mate. Considering that recommended mounting of pusher fans is at least 5mm from the actual core.

  6. #6
    Sidetracked BMWTurbo's Avatar
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    Mounting a pusher fan directly onto the radiator core will be fine.

    With the fan mounted and touching the core you will not get any spillage out the side as this is what the fan cylindrical shroud is there for.

    If you want to mount it 5mm from the core, then use some adhesive backed closed cell foam or rubber to space it and seal it against the core in the one application.
    Last edited by BMWTurbo; 22-04-10 at 03:39 PM.

  7. #7
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    ^ this guy
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  8. #8
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    Yeah the best you can do is put it right against the radiator, maybe if you have multiple fans you would want some kinda 'breaker' between them to solve interference problems, but it kinda depends on what the particular fan is like

    Basically if you put a shroud on a pusher fan, it will be good when the car is stationary, but it will just limit the airflow significantly when the car is moving at a decent velocity.

    Once again, depends on the specifics but I think that's a decent rule of thumb.
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  9. #9
    Gas Turbine enthusiast da9jeff's Avatar
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    just a thought, how come you never see fans on intercoolers? would there be much gain from a couple of thermos tacked on the front of my FMIC?
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  10. #10
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    Quote Originally Posted by da9jeff View Post
    just a thought, how come you never see fans on intercoolers? would there be much gain from a couple of thermos tacked on the front of my FMIC?
    Fans are only required for low speed stuff, after about 60kms the force of the air getting forced thru will keep a car radiator cool, its easy enough to stay of boost at low speeds.
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  11. #11
    Gas Turbine enthusiast da9jeff's Avatar
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    good point
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  12. #12
    Sidetracked BMWTurbo's Avatar
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    Some 4WDs have thermo fans fitted to intercooler from the factory.

  13. #13
    Registered User matty12's Avatar
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    i would say thats more to do with high engine loads/low speed ie in the sand n shit.

    Also they are normally ontop of the engine not infront of the rad.

  14. #14
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    Yeah or even going up hills at high load, very different reasons.

    Might want one on a turbocharged car that does a lot of burnouts? Never thought of that until then...
    LESS WEIGHT MEANS MORE FAST!

  15. #15
    Non player character GTSBoy's Avatar
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    Quote Originally Posted by Hezath View Post
    Basically if you put a shroud on a pusher fan, it will be good when the car is stationary, but it will just limit the airflow significantly when the car is moving at a decent velocity.
    I wasn't talking about a big arse shroud that covered the whole radiator front with a hole in it to put the fan. I was just talking about shrouding around the edge of a pusher fan to force the air air to go through the core. Mounting it 5mm away from the core is not incompatible with that thought, a la BMWTurbo's post.

    I really don't know why I have to explain shit like that though. You cunts should be able to start with the premise that I didn't post something utterly fucking stupid, and then choose the meaning of the post that would be compatible with that premise and not go the other way.
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  16. #16
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    I wasn't suggesting that your idea was completely retarded, you don't need to have a huge shroud to reduce the effective area of a radiator by a decent amount - I think you will find even something 'small' will interfere with the airflow a fair bit
    LESS WEIGHT MEANS MORE FAST!

  17. #17
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    Quote Originally Posted by Hezath View Post
    I wasn't suggesting that your idea was completely retarded, you don't need to have a huge shroud to reduce the effective area of a radiator by a decent amount - I think you will find even something 'small' will interfere with the airflow a fair bit
    Yeah GTSBoy, you should pay more attention to what this bloke can teach you about thermodynamics.
    Don't worry, thats just the self-preservation instinct, in my experience you can safely ignore it.

  18. #18
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    This is ridiculous, I started posting a few days ago and you're cracking the shits because I'm not aware of how much each individual person on here knows. There are smartarses and dumbarses on every forum. Give me a fucken break, I wasn't doing something sinister
    LESS WEIGHT MEANS MORE FAST!

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