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Old 01-16-2013, 12:31 PM   #25
let's keep going...
geometrician's Avatar
Joined: May 2008
Location: West-By-God Virginia
Oddometer: 1,034
BillyD the lower temp (200f) fan switch works by beginning to shed heat sooner than the 220f switch.

In heat exchangers the temperature difference (delta) of the source (our radiator in this case) & the sink (atmospheric air) does indeed change the time required to shed heat to come down to (whatever) target temperature. By not allowing the coolant to reach that higher temp you're already 20 degrees closer to your target temp.

Wattman did extensive testing on cooling systems & found that having a fan on at 60+mph lowered the coolant temp 11f- albeit on a "lowly" KLR. Seems our bikes would fare better as the back area of the radiator is quite cramped

I've turned fans on before I rode into deep sand to pre-cool, which will allow you a few more minutes of run time before the bike heats up- sometimes it's all you need in a tight section before you can make some speed to bleed heat off. I'm talking about the +90f/80% humidity of America's South, don't know how it would work in the dry Southwest

Originally Posted by pdxmotorhead View Post
I'm still interested in trying waterless coolant in my 950. I like the idea of zero pressure in the cooling system
Are you referring to Evans Coolant? That stuff is strange. Some dirtbike racers swear by it, others have destroyed their top ends because it doesn't "boil off" and give the rider a visual clue to overheating. It's expensive (+$40/gallon) & your system must be flushed with Evans Coolant & discarded to remove all old fluid which would be pricey on our bikes. If you are on a trip you can't add anything other than Evans to your radiator/coolant tank should you develop a leak. It's also VERY slippery and can create water pump & head gasket leaks- and our LC8's already have a tough time keeping their coolant behind the water pump seal. It stinks & is difficult to wash off your hands & clothing...YMMV Not sure about "zero pressure"- if you heat a closed system you are going to increase its pressure- one of those pesky ThermoDynamic Laws

Stick to a wetting agent with standard coolant- I used Redline concentrate

someone ask for the part number for the 2nd fan shroud... here's the link
'06 KTM 950 Adv 'S'
'03 KTM 250 EXC
'87 KLR650 - <200K miles "Like the Energizer Bunny, just keeps going & going..."

geometrician screwed with this post 01-16-2013 at 12:42 PM Reason: added 2nd shroud link
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