Defender Viscous fan vs Electric fan





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  1. #1
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    Default Viscous fan vs Electric fan

    Hi guys!

    I thinking of removing my viscous fan on my Tdi and replacing it with a 16"/17" electric fan from the States. or maybe even 2 x 13" fans.

    What's your thoughts on this? will the electric fans supply enough air to keep her cool? has anybody done this before?

    pro's and con's?

    THANKS!!
    Grond Monster

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  2. #2
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    Don't do it, unless you can put in some sort of cowling that is effective. Most of the electric fans you buy, can never compete with the CFM of a viscous fan.

    I run 2 x RunX fans on my LC80TD and on a really hot day, towing a very heavy load, up a very steep hill, I can get the gauge to start creeping up. To control them, I fitted a CH solenoid and an inline temp sensor to know when to switch them on.
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    I agree with Henris

    Not sure of the reason why you want to do this and if it is that your old viscous is not good anymore, rather replace it. I have replaced my tdi's viscous in Feb this year and paid R855 for a new one from Landy Parts. As said previously here, I tow my echo3 anywhere and can go flat-out up any incline and the temp needle never moved over the halfway mark. EGT's also stay well below 720 deg. The tdi is very reliable as it is and adding more electrics, is moving backwards in that regard, in my opinion.

  4. #4
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    Thanks for the advise guys!

    My viscous fan is still running fine, just thought I might gain a few kW's by removing the viscous. also, I'm thinking of doing a overland trip, and I don't want the viscous to pack up in the middle of nowhere. rather have two electric fans that kicks in automatically, or manually if the need exists.

    Maybe just take an electric fan with, to get me out of trouble if something happens.

    what is the CFM's of a vascous fan on the Tdi's more or less?

    cheers
    Grond Monster

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    1974 Series III SWB - "UNTAG" -
    2010 Defender 110 HCPU - "Gorrila" -
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  5. #5
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    Grond Monster,
    I've gone this route in my TD5, unless you are willing to spend a couple of thousand on a good set of fans, rather stick with the viscous.

    As said above, you need a decent cowling with the electric fans, and to swith them on manually.... iwould not take that chance, you might miss the heat creeping up.

    Speak to hot4cold regarding fans, but it is probably cheaper to buy a spare viscous.
    Bertus,

    2002 Defender TD5 HCPU, with Lexus V8

  6. #6
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    I know theres a Kenlowe electic fan kit available that supposedly very good? -From the UK, about 170 Pound.
    A legend in his own mind

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    For that price get the viscous.

    How do you bush fix a viscous when it goes? Self tapping screws can destory the fan in all sorts of creative ways. Stuff like having a fan fin make a nice hole in the bonnet or radiator
    Sold Land Rover 110 Tdi Hard top.
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    Gemini (Mike), from the UK currently visiting SA, is running a Kenlowe fan on his 200Tdi, apparently with no problems and have been coping with whatever Namibia and Botswana's weather could throw at him.
    camelman
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  9. #9
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    Quote Originally Posted by O.B. View Post
    For that price get the viscous.

    How do you bush fix a viscous when it goes? Self tapping screws can destory the fan in all sorts of creative ways. Stuff like having a fan fin make a nice hole in the bonnet or radiator
    I once fixed one and it lasted quite some time... Drilled holes on a triangle and put M6 bolts trhough and pulled it together...

    I would ratehr struggle with a viscous than an electrical fan packing up...
    Hennie
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    Disclaimer: The views expressed by me in the above thread and replies are based on my personal experience and perceptions, which may be subjected to change from time to time.
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  10. #10
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    Quote Originally Posted by Grond Monster View Post
    Thanks for the advise guys!

    My viscous fan is still running fine, just thought I might gain a few kW's by removing the viscous. also, I'm thinking of doing a overland trip, and I don't want the viscous to pack up in the middle of nowhere. rather have two electric fans that kicks in automatically, or manually if the need exists.

    Maybe just take an electric fan with, to get me out of trouble if something happens.

    what is the CFM's of a vascous fan on the Tdi's more or less?

    cheers
    Unfortunately there are no free lunches. What you gain on the merry go round you will lose on the swings. The viscous is driven by direct engine power while the electric fan gets its power from the battery which is then "topped" up by the alternater which in turn is driven by the engine. Even more losses.

  11. #11
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    Monster, I have done this on my 2.2l petrol. I would not recommend it on your diesel vehicle. You have much more heat to dissipate. Keep in mind that the average viscous fan uses 2-3kW to run where as the electrical one's use 0.6-0.8kW. The energy used by the fans are proportional to their effectiveness.

    Using less to dissipate will give you less dissipation. This means you will have to increase efficiency of the entire system. Increasing coolant in the system, radiation area of the radiator, etc. All these have a cost implication.

    Also as mentioned you will need a decently designed cowling. Mine was very simple to make as my fan is nearly as big as the radiator, but might not be the same in your case.

    There are pro's and con's to both, but on the TDi the proven technology will be the victor.


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  12. #12
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    Quote Originally Posted by O.B. View Post
    For that price get the viscous.

    How do you bush fix a viscous when it goes? Self tapping screws can destory the fan in all sorts of creative ways. Stuff like having a fan fin make a nice hole in the bonnet or radiator
    self tapper works but then keep revs under 3000.
    as a temporary measure, it will help you get somewhere where you can get the viscous swopped out.

    Land Rovers never die, they simply become organ donors!

  13. #13
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    Thanks guys,

    It seems like sticking to the current config is the way to go.

    During slow off road work, the viscous fan turns slower than a electric fan would. Thus during off road work, wouldn't an electric fan supply more air?

    so here is a question:

    Currently I have a smaller fan on the front of the radiator for the aircon, that puches air through the radiator. right? so if I see that the temp is rising (or while doing slow off raod driving), will it help if I switch on the aircon fan to supply more air?

    stupid question or not?
    Grond Monster

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  14. #14
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    yes it will help. now days those fans are generally linked and will switch on between 95 and 100 celcius. but you want it to come in earlier. You can get it wired with a manual on switch.
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    been there, done that, got the shirt (and shi_t)its not worth it - will be removing the electric fans
    Francois Engelbrecht
    3.0 Hardbody DC 4x4

  16. #16
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    the viscous clutch works like a thermostat.
    the hotter it gets, the more it couples and the higher the rotational speed relative to engine speed.
    even at idle when fully clutched, it pumps quite a bit of air.
    IMHO a viscous is actually more efficient than an electric fan with the only additional power required is the friction of the belt and the bearing.
    when accelerating, the electric fan has a marginal advantage in not holding back the motor but you don't get power for nothing.
    whether pulling power off the crank or off the alternator, it is the same difference.
    the only advantage is that with electric, no fan runs until the engine is up to operating temperature. even here the viscous draws very little power as it slips when cold and will only pick up speed when it senses the heat coming off the radiator is higher than expected and then clutches in.
    if it was a case of coparing the electric fan with a static fan, it would be a different kettle of fish.
    claims of power savings of around 8% of an electric over a viscous is i believe sales talk.
    for around R1000, it would be worthwhile to replace the viscous every 100k km.

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  17. #17
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    Quote Originally Posted by Willied View Post
    ............. The energy used by the fans are proportional to their effectiveness. ...............................
    Quite so. On the 80, they suck 36A on startup and 18A on running.
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  18. #18
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    I did this conversion on my 1992 BMW 316i.

    We also changed the thermostat to one that opens( 88 Degrees instead of the 95 degrees) at a lower temp & temp sender to one that activates the electric fan at a lower temp (as the car had the viscous fan & an A/C fan in front of radiator) now it has the A/C fan & another fan on the back of the radiator thats the same size as radiator. Now the fans kick into slow speed when temp hits 90Degrees & if it goes up to 99Degrees then it goes to speed setting 2.


    since doing the conversion I have not had any problems with over heating etc & could feel a slight increase in power.

  19. #19
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    On a platkar I have done this before, but I think the viscous is the best. My Nissan viscous and water pump is a complete unit ( I can not buy the viscous coupling separate). So if my viscous goes, I have to take the front of the engine apart and replace water pump at the same time. Still I have seen too many guys have problems with electric.

    I would love to have my car quieter with the electric, have the ability to switch off during water crossings, score the 3kw half way up the hill when the viscous drains my old donkey.... BUT, I think viscous is more reliable. It does not mind water or mud and has no electrics to go south and short out. YES mud does affect it. If it gets caked with mud, it slows the action down slightly as the mud changes the way it "reports" the heat back to the viscous via the little metal strip on the outside. But that is much easier to fix than an electric fan that has burned out due to a short in water/wet conditions.

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  20. #20
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    Buy a new one and install,
    keep the old one as a spare for your trip.
    Hopefully you wont even need it.

    I'm with Mr Sani, stick with the viscouse fan.
    Chris

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