Range Rover Blues Posted November 11, 2011 Share Posted November 11, 2011 I rang Kenlowe a couple of years ago for advice about cooling, I was having problems when I towed. Their engineer advised me NOT to buy any electric fan, even theirs, and fit a new viscous hub to the fan if I was sure the radiator wasn't to blame. A viscous will shift more than twice the air that a pair of electrics will. He also advised a second oil to air auto box cooler. I have electrics on Blue though because it's an off-roader. It does seem to use them a lot when greenlaning and that used to cause me problems with alternator belts, even with twin batteries, until I fitted a thicker Vee belt. Tanuki is right, a hot engine is efficient and clean, though I do remember reading that the original Buick V8 was most efficient at around 70 degrees which is obvioulsy contradictory. We all know these engines are not perfect but if you keep the cooling system in good order then the temp should never rise about 19degrees, which is hardly likey to cause damage. Quote Link to comment Share on other sites More sharing options...
p76rangie Posted November 11, 2011 Share Posted November 11, 2011 A viscous will shift more than twice the air that a pair of electrics will. Can you please supply these figures. What electric fans are you using the airflow data from? At what revs are you quoting the airflow for the viscous unit. A viscous running at 5,000rpm will shift more air than a good set of twin electric fans. At 2,000 to 2,500 rpms my electric fans pull more air than a viscous. There are lies, damn lies, and statistics. Quote Link to comment Share on other sites More sharing options...
Range Rover Blues Posted November 11, 2011 Share Posted November 11, 2011 OIl temps can reach as high as 130 degrees though, so I wouldn't worry too much until the engine overheats. All V8 RRC had an oil cooler once the 3.9 was introduced. Quote Link to comment Share on other sites More sharing options...
teabag Posted November 11, 2011 Share Posted November 11, 2011 Can you please supply these figures. What electric fans are you using the airflow data from? At what revs are you quoting the airflow for the viscous unit. A viscous running at 5,000rpm will shift more air than a good set of twin electric fans. At 2,000 to 2,500 rpms my electric fans pull more air than a viscous. There are lies, damn lies, and statistics. As the viscous coupling operates on temperature and not on RPM how do you compare the performance of that with the RPM of an electric fan, your data on engine revs vis engine temperature and how you obtained it also the specification on your "electric fans" it would also be interesting to the forum.. Quote Link to comment Share on other sites More sharing options...
p76rangie Posted November 11, 2011 Share Posted November 11, 2011 As the viscous coupling operates on temperature and not on RPM how do you compare the performance of that with the RPM of an electric fan, your data on engine revs vis engine temperature and how you obtained it also the specification on your "electric fans" it would also be interesting to the forum.. I think you will find that on a viscous unit it is only the temp that engages or disengages it. The airflow while engaged is determined by how many revs the engine is doing. As with the airflow with electric fans, you are making the common mistake of assuming they are all similar, that could not be further from the truth. Then you have all the issues on how people wire them up and the speed they will produce, etc, etc. Quote Link to comment Share on other sites More sharing options...
Range Rover Blues Posted November 12, 2011 Share Posted November 12, 2011 Viscous fans are designe dot reach their max speed at around 2,000rpm on the crank unless they are getting hot. Often you will hear the fan running at start up until the fluid is thrown into the correct chamber, it settles overnight. IF a viscous fan draws 5 BHP, then that means you need 3.7Kw of electrical power, assuming 100% motor efficiency, to deliver the same fan power by electrics. That's 310 amps at 12 volts. Quote Link to comment Share on other sites More sharing options...
p76rangie Posted November 13, 2011 Share Posted November 13, 2011 Viscous fans are designe dot reach their max speed at around 2,000rpm on the crank unless they are getting hot. Often you will hear the fan running at start up until the fluid is thrown into the correct chamber, it settles overnight. IF a viscous fan draws 5 BHP, then that means you need 3.7Kw of electrical power, assuming 100% motor efficiency, to deliver the same fan power by electrics. That's 310 amps at 12 volts. I love your figures. Most authorities quote that the engine fan pulls between 1/4 and 1/2 hp. This means that in 12 volts it would require between 15 and 30 amps. My electric fans pull around 30 amps EACH at start and then run at 15 to 20 amps each. So they are producing over 1/2hp. But then we get down to the efficiency of various fan designs, or whether one fan at the centre cools better or worse than 2 fans covering most of the radiator surface area. Also whether a fan sitting a couple of inches away with a loose fitting cowling is better that two fans sitting millimetres away. etc, etc. A viscous fan is designed to lock up when the engine is hot enough to require it. Yes it does spin other times, only because the design does not allow for it to completely disengage. So when they are required, and engaged, they will largely change speed with the engine. Even at idle you will hear the fan start to roar when it engages. It does not matter what it does when the engine is not hot enough to require it and I would say that you have a faulty fan if it is engaging at 2,000 rpms when the engine is not hot. Below are the fans I use. For those without a convertor, they are twin 13.2 inch fans Quote Link to comment Share on other sites More sharing options...
Range Rover Blues Posted November 20, 2011 Share Posted November 20, 2011 Can't remember the figures, but they were quoted to me by the applications engineer at kenlowe, so I'd guess he knows what he's talking about. As for how much power a Visocus fan draws, I don't know. I used 5 hp because that's what another poster had suggested. I can't find anywhere on the 'net that gives a reliebale figure for the power consumption of a viscous fan, but if you read herehttp://forums.tdiclub.com/showthread.php?t=322035 someone mentions 22BHP on a big V8 pickup. I doubt the 8% of total engine power claimed in some adverts too. This http://www.aaroncake.net/rx-7/efanmyth.htm was quite amusing, if long-winded. I can tell you I rmeoved the fan on our TDi and took quite accurate measurments of fuel consuption. it made no difference whatsoever. On our off-roader and TDi I use electric fans, fo all the normal reasons I guess. On the LSE where cooling is the most important, I use a new visous fan. It works, I don't have to worry about it, it does the job. P.S. somewher eint he back of my mind I'm thinking there was a 5 somewhere in the numbers, perhaps 5 or 5,500CFM?but almost twice what the H/D 12 inch fans Kenlowe could offer can shift. Why do you think LR fitted viscous fans? there's probably little in it in terms of cost Quote Link to comment Share on other sites More sharing options...
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