Thanks for everyone's input. Mathematically, we have a radiator that's 12" x 6.5" or 78" sq. and a fan that's 5" or 19.64" sq. Bottom-line is COVERAGE is only 25% (at best) in this single radiator system.
Jeff--With nerf bars, the coffee maker, mini-frig, 25" plasma...simply for me there is no room for a 2nd radiator. I take it with your duals, you have no overflow reservoir? I've always envied your dual rads, but it'd be over $600+ just to add the rad and fan not to mention the cost to get it fit and rigged. $1,000 all-in???
David Nichols--A lot of the time I'm in deserts in deep sand and often loaded down with kit, so 20 mph+ is strongly desired but not always possible. Hills with deep sand? Forget it. Once you lose momentum in a long stretch of deep sand and you see the needle peg right and engine dieseling, you realize the KLR has limits. Simply, there's only so much heat that can be transferred out of a fluid (mix) with the stock setup covering 25% of surface area. But otherwise I agree if you're in traffic somewhere running a bit hotter than normal, yeah, ride faster. I have over 34k miles on this KLR and maybe 20% are street. But I agree with you, for most 80 street/20 off riders, overheating simply isn't and will never be an issue. Clearly slower speed is the issue here while not inhibiting free-flow cooling solutions at speed.
dat brooklyn bum/da Vermonster--I have heard of others using Ninja fans and they're cheaper than stock fans. This could add a bit more cfm but noticeable? How much?? If you inspect the fan/rad and what is actually covered flow-wise (pre-2008 models at least), it's inefficiently covered @ 25%. Again, a 5" diameter fan covers a 12" x 6.5" radiator = poor. Two fans with a single shroud (like some cars) would be a much better design plus add redundancy. As for any system, I prefer always distributed and redundant over "heavy duty."
gregc--I put my KLR through demanding conditions regularly (2 blown engines). Add in hot ambient temps and it's not much to push the KLR cooling capacity deep into the red. But to answer your question, I don't think two (2) 5" stock fans would fit. Plus, running two OEM fans would likely draw 9 amps--at least initially. Under the OEM fan there is approx 5" x 6.5" of space. You could fit one 4" fan or perhaps a cluster of two (2) 2.5" fans in a separate shroud (this wouldn't be my first choice but worth researching). There are potential options to add more surface area while increasing cooling rates with the right fans + shroud combo. Yet, at this point, I don't think we need to double capacity. An increase of as little as 25% might serve us perfectly well. But why not also add safety margin with redundancy of a secondary cooling fan? For example, imagine at Temp 1, fan one initiates. At Temp2, fan #2 initiates assisting #1 until Temp1 is achieved. If one fan fails, you still have coverage.
revmaaatin--Straight distilled water has its limits--most notably a lower effective vapor point and evaporation. But you are correct water does cool better than ethylene glycol coolant because of water's higher heat carrying capacity per unit. However, coolant's higher vapor point means it can continue absorbing heat at higher temps. So, while a 100% distilled water mix would cool best, you still need to consider things like evaporation, corrosion inhibitors and lubricant for mechanical water pumps (seals). Perhaps use a 90/10 mix to get a touch of the lube/anti-corrosion benefits and yet still enjoy a potential of upto 20 degree decrease in cooling temp running near straight water? One additional improvement I'd consider is raising the vapor point of a 90%+ water system by increasing the release on the radiator cap (e.g., move from a 15-18 psi cap to a 23-25 psi cap). For every point of system pressure increase, the boiling point of water will increase by 3 degrees. This higher boiling point helps reduce evaporation losses, water pump cavitation, and heat-soak-induced-after-boil. In other words, a higher-rated cap will keep the water from blowing out while adding more capacity for it to continue to absorb heat at higher temp. Ultimately, if your marginal rate of heat build is higher than your cooling system's marginal cooling rate, it's only a matter of time before the heat reaper arrives regardless of fluid choice/mix. Here I'm most interested in proven gains in marginal cooling rates via surface area and flow (speed). Like David Nichols said,...just speed up and problem goes away.
--- In
DSN_KLR650@yahoogroups.com, Jeff Saline wrote:
>
> On Fri, 06 Jul 2012 04:41:40 -0000 "boulder_adv_rider"
> writes:
> > The current fan on my 2004 685 is inefficient and underpowered for
> > demanding tasks including hot deserts.
> >
> > Question #1: Has anyone successfully installed a larger fan?
> >
> > The radiator is roughly 12" x 6.5" and yet the OEM fan is only a 5"
> > diameter blade. In other words, you have a small, round 5" fan
> > serving a large rectangle--very inefficient--serving 1.3 liters (44
> > oz) of cooling capacity. I'm considering modifying any type, size
> > and/or style of pull-type fan (7" Procomps, 12v computer fans, etc.)
> > to replace the OEM fan and/or add another fan or cluster of fans
> > below the OEM fan to increase cooling capacity. Got data anyone?
> >
> > Question #2: Has anyone successfully produced an OEM-grade shroud?
> >
> > Over the years I've seen a mod(s) to divert the air flow to "act"
> > like a shroud but haven't seen a production-grade shroud made out of
> > thin metal or plastic. I'd be happy to fab one but in reality it's
> > cfm @ speed over the entire radiator that I'm more interested in now
> > (Question #1).
> >
> > Ultimately, I'm considering R&D-ing whatever but don't want to
> > re-open Pandora's box if someone's already been seriously maimed
> > researching this. Thanks, all.
> <><><><><>
> <><><><><>
>
> Best I've done is install a second radiator and it too has a fan. With
> the added cooling capacity the fans aren't as important.
>
> Best,
>
> Jeff Saline
> ABC # 4412 South Dakota Airmarshal
> Airheads Beemer Club
www.airheads.org
> The Beautiful Black Hills of South Dakota
> 75 R90/6, 03 KLR650
>
> .
> .
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