Second Fan: BDCW vs AdvMachines

This is unfortunately a incorrect statement. The 990 does not leverage a ECU's capability to turn the cooling fan on/off, this is only performed by the thermo switch that threads into the right radiator tank.

EDIT: Also, to my knowledge, there is not a lower temperature thermostat, the device that regulates the engine coolant temperature. The Thermo switch is the device that tells the fans to turn on/off dependent upon a set temp range. OEM temp is ~220F on. My experience with the lower temp thermo switch (~200F on) is as follows, and I almost completely agree with BillyD's statements, with deviation on that with the fans coming on sooner there is a greater potential for a period of "rest", so MAY allow for the system to catch up sooner. Granted, we are not increasing the capacity of the heat exchanger, we are increasing the exchange of heat by forcing the flow of air through the exchanger (radiator), still there are limits and in some cases the limits will still be met when the engine is producing more heat than can be rejected to the ambient air.

EDIT2: What I typically experience with the addition of the 4" fan on the right side of the radiator (my experience is with the ADVmachines fan so I cannot speak to the BDCW fan) is a reduction in fan cycle time by about 40-50%. This is unloaded and with the engine idling on the lift. The cycle time between on and off is reduced again by about another 30% when adding the lower temp thermo switch, this switch turns both fans on at the same time. During normal riding the fans will cycle more frequently and will tend to come on sooner (with 200F switch), but again will turn off sooner as well. The engine temperature is still regulated by the thermostat and most reports that I have heard back from other people who use this system say that typically the gauge rarely exceeds 4 bars (950), and almost never goes past 5 bars unless in extreme conditions and loads. Even at 6 bars of engine temperatures the cooling system should still be "stable" and not puking coolant uncontrollably.

Personally I run the ADVmachines rally fan.

Wetting agents, their primary benefit is that they help keep the water in contact with all the surface in
the cylinder and head assembly, I've seen testing done and it reduces head and cylinder hotspots.
Even if your heating the overall engine up this reduces the chances of a area fatiguing and giving up on you.
Like between the spark plug and valve guides...

I'm still interested in trying waterless coolant in my 950. I like the idea of zero pressure in the cooling system..

Cheers.

Dave

WTF? I think I'd like to know more, please expand.

My fan bearings are a bit gritty since I ran the lower temp switch. In off-road the fans were always on and when I was behind other riders their dust gritted up the fan bearings over a season of riding.

I put the stock temp switch back in, made sure the system was burped properly (which is a royal pain) and I never had overheating issues since then. The only time I came close was a 10 minute mountain climb in first gear and high revs the whole way up.

I have the ADVMachines bracket and I like it, but had to add a fan shroud to the right side fan to keep the gas in the right tank from boiling/pressurizing.

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

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

One minor note. You can add water to Evans Coolant in an emergency, but if you exceed 5% they recommend you refill with Evans ASAP. That said, I considered it for my dirtbike, but decided to stick with a water based coolant.

Agreed. Pre-cooling (by switching on the fan) might help make it through a transitory situation without boiling over.

My comments assumed a more steady state situation, such as when I'm usually stuck in those tight technical sections for extended periods of time...alone...dying of thirst...crying for mama.

Here's a somewhat relevant graph. Switching on a fan increases air flow (MPH) and resulting in increased rate of heat rejection.



Per geometrician's comment, increasing the differential between air and coolant temperatures, would also increase available cooling, albeit temporarily in his example.

Alternately, if you were to substitute inlet-outlet temperature differentials (delta degrees C) for coolant flow (GPM) and air flow (MPH) rates on the graph, the graph would look largely the same. In other words, the higher the coolant temperature drop through the radiator or air temperature increase across the radiator, the better heat transfer performance at any given flow rate.

Been using Evans in the 565 for years without issue. Granted, it could be overheating and I wouldn't know it. Ya got me there.

On my old 640 i had a switch to turn the fan on whenever i wanted so if getting stuck in traffic or in the tight stuff i'd just switch it on to keep temps down before it got to come on by its self, has anyone done this to a 950/990

I put the BDCW second fan and Rally Raid thermostatic fan switch on for a long trip to Italy last summer. Turns out it was their hottest for about 10 years and stayed in the high 30s, low 40s for most of the time. Phew. I reverted to the stock fan switch half way through as the fans were coming on too much of the time for my liking. The OEM fan has a shield that helps divert the blown hot air away from you. The second fan does not and blew the air straight at my leg.....


Billy D can vouch for the heat. We bumped into each other a couple of times in the same afternoon in Tuscany after a good lunch at Volpaia. Hey Billy how goes ?

Tim

It is possible to mount the OEM fan diverter/shield to a ADVmachines rally fan with mild modification. The part is fairly inexpensive at $4.59 USD.

KTM PN: 60035044050

http://www.evanscooling.com/

This stuff gets used in a lot of heavy diesel engines,, commercial rigs etc..

The big advantage that tempts me is that you can use a non pressure radiator cap.
So the cooling system has zero pressure in it.. That should reduce load on seals and
reduce the potential for gasket failure.

Stuff is expensive, but we don't need much..... :)

Dave

ADD: LOL see a few others answered.. Should a read farther.. All good information...

It was indeed very hot in Tuscany when we bumped into Tim and Lucca. What a great place to ride.

Hey, Tim, looks like we'll be renting dualsports and doing off-road in Sardinia the last week of June. Alternately, come over here and ride some desert. I just picked up a guest bike. Then we could do some real fan testing.

Sardinia will be fun Bill ! Never ridden there myself but been on foot a few times. Thanks again for the invite for proper fan testing. one day hopefully.

Luca and I are just starting to plot a possible adventure tour out to the black sea and back this spring. I'll try and post a ride report here if anything comes of it.

Anyway back to fans......

Have fun.

Wrong way around - increased pressure increases boiling point, reduced air pressure decreases boiling point. Which is why you can only have a luke warm cup of tea on top of Mt Everest. And which is why the increased pressure of a pressurized cooling system raises the boiling point so you reduce the chance of your cooling system boiling (which is where it loses it's efficiency). However if the liquid in your cooling system doesn't boil (or already has a very high boiling point) than this a moot point - you don't need any pressure to increase the already high boiling temp.

I've never converted any of my bikes to Evens, but have considered it due to its requirement in Rotax engines used in lots of homebuilt aircraft...


Read up on it if you like...


http://www.evanscooling.com/news/press-releases/rotax-aircraft-engines/



.

Also, the Evens Coolant has no water to boil at relatively low temperatures.. That's why you can run zero pressure systems at altitude.

About 40 bucks a gallon so its cheaper than our motor oil....

Dave

The only concern I would have is that if the engine is running hot for whatever reason - with water it boils and you know you have problem (albiet a problem that could leave you stranded!) hopefully before any permanent/actual damage is done, but with fluids that don't boil (or have very high boiling points) you could be overheating without knowing it and damage the engine.

I just acquired a second fan, spliced it right into the first fan's plug, and zip-tied it to the radiator. Been running it for 1000km now, 50% of the off-road. All in about 30 deg C heat. I actually found I was getting to 5 bars earlier than before, and staying there, even once I was up and running at a good 60 kph :huh Fans were coming off and on quite frequently.

I figured that when the second fan was off, it was actually impeding the airflow where it used to just go straight through once you go moving. When it heated enough, the fans kicked it, cooled it just below the threshold (which is still in 5 bar territory), then turned off again, blocking the airflow. So it just kept bouncing around the 'low' 5 bar mark.

Of course, I just noticed a fair part of my grill was packed with mud....that probably didn't help.