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two fans on radiators (dual fans, fan on each radiator)

Old 09-20-2011, 06:36 PM
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two fans on radiators (dual fans, fan on each radiator)

i did a bunch of searches, this could be a better topic for someone to search for the question i had.

its dark out and i didnt look if there was ample clearance. but i had a random thought while reading about something else on the forums.

would it be beneficial in the southern environment i live in, to put a fan behind both radiators? off same sensor that will measure the optimal 220... or tap a hole for a secondary sensor in the left radiator for uniform temperature measurements, with independent fan operation? if a fan mount would in theory fit behind the left radiator... tbd

honestly, its so hot and humid during the day, you dont notice which side of the bike is hotter or cooler coming from the engine.. its all just hot (cant wait for winter months)

my fan kicks on and off alot between redlights, never goes above a little past middle on the temp gauge. i run engine ice as well.

just wonder how high the temp gets on the radiator without the sensor and if having a fan on that radiator as well would help over all cooling so my fan wouldnt need to be tripped as often as it is.

i made a parts list, and half the parts are common nuts n bolts. and to find a used fan assembly that works. tack a mount onto the existing underside of the radiator of a mount and wire it up

thoughts?

i like projects btw
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Old 09-20-2011, 06:49 PM
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A cooler engine is a happier engine
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Old 09-20-2011, 06:51 PM
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Thinking aloud here: wouldn't having two fans cause the fans to "trip" more often? If they cool the bike down faster, they will deactivate faster, allowing the bike to heat up sooner, then the process starts all over again.

My personal thoughts in dealing with the cooling system are that the stock setup is handled pretty well... if it's all functioning properly, you can't improve it that much. You can certainly have it operating under optimum temp if you want to. They're not like computers where the colder they are, the faster they run

Currently, I am slowly poking around making a new oil cooler that is larger and located where HRC put it (behind the exhaust header, under the front cylinder).

I guess what I'm saying is that there are probably other projects that you could come up with... I also saw somewhere that a person put an electric water pump on their 'Hawk, reducing a slight amount of resistance on the motor and saving a little weight.

All with a grain of salt, those are just opinions!
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Old 09-20-2011, 07:07 PM
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I doubled the air flow of my cooling fan, with a SPAL fan. With no mods of the wiring, mounting bracket. If you research, or ask the electrical gurus on the forum..
SPAL fans use less amps to start up, and run... And show MORE cfm of air moved...
Just a suggestion... from experience...
Both the RC51s, and aleast one of the Shawks have a SPAL fan...
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Old 09-20-2011, 07:24 PM
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i was kinda interested in the temp differences between one radiator on the left with a fan and the other without on the right. i never tested or thought about it until i was reading a post about single radiators under the tail that overheated with one fan. just got me thinking. i do alot of that!

7moore7 : Thinking aloud here: wouldn't having two fans cause the fans to "trip" more often? If they cool the bike down faster, they will deactivate faster, allowing the bike to heat up sooner, then the process starts all over again.
i dunno.. there is only one coolant flow... but there are 2 radiators and a fan one one side of flow and another on the other side without a fan, with two (or one) sensor, shouldnt overall work effort be reduced by more airflow per cycle?..
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Old 09-20-2011, 07:39 PM
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Well, I actually have one of those undertail radiators ... but the issue with them isn't necessarily the fans. Where they are limited is that you don't get nearly as much airflow from speed as you do with a front mounted radiator(s). In other words, when your bike is moving, there is quite a bit of airflow moving through the rads without any fan. The rads are even angled slightly to create a low pressure system right behind them to draw the air through. So, by nature, your bike heats up at stoplights, etc. With the undertail rad, there is much less natural airflow through the radiator, so it has to be supplemented with an extra fan.

OK, so what I was thinking with the fans tripping more often is that if you have two of them on a stock bike, they will turn off and on more often b/c they will cool the bike off faster. So if it reaches 220, the fans will kick on and cool it off till it reaches 112 or so... this will take more time with one fan, so it won't kick on and off as often (cause it's on for a longer period of time). With two fans, they're both running (more power draw) but will cool it off faster. To be honest, I'm not sure which is better... the additional fan will regulate the temp a little quicker, but adds weight and complexity.
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Old 09-20-2011, 08:09 PM
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missing the point of left to right comparisons in temp.. there is always an in and an and out. flow from one to the other passes back over another area in someway shape or form of heat dissipation
better cooling going back into the engine was my thought.

i really havent looked at how the coolant lines are laid out. was a 6pk idea! gn hopefully someone else chimes in tomorrow morning

cheers

Last edited by intoxxx; 09-20-2011 at 08:13 PM.
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Old 09-20-2011, 08:12 PM
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Oh so you're wondering if putting a fan in the "hotter" (left side) radiator will make any difference? Or am I actually missing something entirely? lol

Gotta document the 6pack ideas... otherwise you'l never remember!

Last edited by 7moore7; 09-20-2011 at 08:14 PM.
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Old 09-20-2011, 08:19 PM
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I think the biger issue is the current draw of 2 fans. It would exhaust the battery since the very times you would need it are when the charging would be least (slow traffic).

I bought a low temp fan switch but I thought it kicked on too often ( kinda all the time).

To combat this issue, I installed a huge oil cooler in front in place of the stocker. This and a cancooler on the oil filter really did the trick and dont require any volts.
Attached Thumbnails two fans on radiators (dual fans, fan on each radiator)-motorswap8.11-026.jpg   two fans on radiators (dual fans, fan on each radiator)-images.jpg  

Last edited by smokinjoe73; 09-20-2011 at 08:31 PM.
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Old 09-21-2011, 03:44 AM
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Originally Posted by 7moore7 View Post
Oh so you're wondering if putting a fan in the "hotter" (left side) radiator will make any difference?
you got it
Originally Posted by 1971allchaos View Post
1971allchaos: I doubled the air flow of my cooling fan, with a SPAL fan
good suggestion, if its possible i'll quadruple the airflow then!
Originally Posted by smokinjoe73 View Post
smokinjoe73: I think the biger issue is the current draw of 2 fans...
would need to whip out a multimeter to measure system draw and stator output at idle, unless anyone knows these numbers offhand
dont know how much play there is with the electrical system loads and stator output @1250rpm

i run all LEDs and 35w HID headlight.
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Old 09-21-2011, 04:27 AM
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At idle, there is virtually no overhead available as stock... Add too much stuff, and you will end up not charging, and get problems... Running LED's and a HID doesn't give you enough overhead to add a fan on idle, really... That's the electical part...

The cooling part is another thing... The VTR is hotblooded... Adding a fan will increase cooling, but like 7moore7 said, it will only cycle the fan more... If you keep the temp constant, it changes slowly... If you drop the temps rapidly, it bounces back just as rapidly... Laws of thermodynamics... Ie the more cooling you throw at the radiators, the more hot-cold-hot-cold cycles you get... So if the idea behind all this is to keep your fan from cycling, it's counterproductive... Swapping the stock fan for a SPAL fan is probably a decent compromise, it adds cooling potential so you don't run the risk of overheating, but it won't overshoot...

Like has been said, swapping to a larger oilcooler is better for the engine, getting more cooling without the heatcycling...

If you really want to have two fans, (for the sake of having two fans!) make them adjustable, and run them on a lower RPM, keeping the temps lower and without cycling...
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Old 09-21-2011, 05:24 AM
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I am running a 1" in-line cooler (similar to this: ModQuad Radiator Inline Coolers Blue 1" | eBay) spliced into the lower rad hose (also had it treated with heat dispersant paint to make it more efficient yet). and it seems to have helped with the cooling. Try runnign Engine Ice coolant too (every little bit helps).

Finally, I also suggest a larger oil cooler (mine is from an EX400 ATV, same as RC51, has 4 rows instead of two). One last item would be to wrap the exhaust header where it runs under teh sump (radiant heat will warm the engine).

Hope this helps.

P.S. I am also running Durbahn air scoops but those are fairly expensive. The above mods are reasonably cheap, and quite effective.
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Old 09-21-2011, 07:00 AM
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Oh yeah, my observation on voltage was based on scientific research of push starting VTRs in hot weather, not printed numbers. Anybody know a good source for SPAL fans? Is there a model that uses them we can pilage on ebay? My current stock fan is craptacular.
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Old 09-21-2011, 07:04 AM
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Best source for SPAL fans is eBay. I suggest you get the 5.2" pusher (what I am running with great success). A manual override switch (to manually activate the fan) is another effective addition....

Last edited by mikstr; 09-21-2011 at 07:07 AM.
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Old 09-21-2011, 10:11 AM
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I went directly to SPAL USA.com to get my fans.. The pusher fans Mikster is suggesting... Part nu. VA31-A101-46S 5.2 in. pusher fan...
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Old 09-21-2011, 10:21 AM
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From what I recall, I was able to source mine cheaper on eBay....
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Old 09-21-2011, 10:34 AM
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Old 09-21-2011, 10:38 AM
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Nice thanks, thats pretty cheap compared to what I saw...
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Old 09-21-2011, 05:04 PM
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thanks for all the great replies today while i was at work.
i will definitely go with the SPAL pusher and also get a larger oil cooler as a starting point.

i was talking to someone today that had an rc51, and had two fans but didnt know if it was stock because they were on there when he got it off a retired track buddy. when i got home i looked it up on hondaparts and they have fiches of both R and L radiators, both with fans.

thoughts on rc51's electrical vs vtr? and why the rc51 is equipped with two fans stock?

Tweety If you really want to have two fans, (for the sake of having two fans!) make them adjustable, and run them on a lower RPM, keeping the temps lower and without cycling...
to clarify one thing, i dont mind if fans are on more often, but you bring up an interesting thermodynamics angle.. the cycling of temps is worse for the engine that cools faster and gets hot faster?
my initial questions angle was from uniform cooling between both radiators.. we are onto something!
i pointed out the rc51 is oem dual fans.
vtr has a sensor in the radiator, rc51 has one at the thermostat

scenarios:

* higher cfm fan. rpm controlled.
fan comes on with lower amp draw than stock
coolant temp lowered slower

** dual higher cfm fans. a lowered temperature sensor. and rpm controlled
fans come on sooner with lowered rpm to come close to stock amp draw
fans start cooling sooner and more often
radiators work in tandem to cool each other uniformly
limiting cycling of temps which tweety pointed out.

thermodynamics vs electronics
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Old 09-21-2011, 05:18 PM
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FWIW, IIRC the SP-1 had a single fan and the SP-2 had duals....
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Old 09-21-2011, 06:18 PM
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Originally Posted by intoxxx View Post
the cycling of temps is worse for the engine that cools faster and gets hot faster?
I think he summarized better what I was trying to say... basically, quicker cycles doesn't help you much. Actually, to be more specific, I don't think it will hurt or help your motor. It is just an extra burden on your electrical system (and a little more weight)

And keeping the rads even in temp isn't that important... what really matters is the temp of the water coming out of the system back into your engine. They could care less how hot they are!

Also, I'm not sure how the RC-51 works, but VTR's have a thermosensor that sends a signal to our ECU in the thermostat. They also have a fan switch (not sensor) in their radiator that turns their fan on... this is the case with a lot of bikes. Maybe the RC-51's fan is controlled by the ECU? This seems so digital when analogue would work better, and I'm too lazy to check
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Old 09-21-2011, 06:27 PM
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Right or left side doesnt matter; its not like it cools right & left halves of the motor. Coolant leaves motor & returns after both rads. Doesnt matter how it gets cooled (or which rad). 2 fans just means cooler temps, even 2 fans on one rad
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Old 09-21-2011, 06:40 PM
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I'd like to challenge the whole point of two fans.

The stock fan works fine just how it is, it is a fan by the way. What doesn't work with how it's setup on a superhawk is how it turns itself off at a certain temp. Point being is if it was manually controlled you could benefit from a quick cool down while moving between lights if you could manually keep the fan on. I've noticed on my 600's with their big rads right in front of the motor, while moving they cool really quick and efficient, but with the header right behind the rad, the motor heats up really fast at a standstill.

The superhawk doesn't benefit from direct air to the rads like a 600, it relies on negative pressure to pull air through, which doesn't work well at slow speeds. Therefore if a fan could aide in slow speed moving you could get the quick cool down you're looking for. I live in Houston, so I know my fare share of hot weather riding.

Instead of monkeying around with a second fan, I would suggest trying a simple manual fan switch.

Also, the big oil cooler idea is great too. Their's a limited amount of motor that's cooled by water, the rest relies on oil to cool it off.
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Old 09-21-2011, 06:45 PM
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Originally Posted by 7moore7 View Post
Maybe the RC-51's fan is controlled by the ECU? This seems so digital when analogue would work better, and I'm too lazy to check
(Again) IIRC SP-1 fan is controlled by a sensor whereas the SP-2s are controlled by the ECU (in case it matters).

My theory in dealing with the VTRs cooling issues has always been to try to get it to cool well enough that the fan never needs to kick in (or as little as possible). It would seem to me that the presence of a fan (when it is not operational) would actually hinder cooling as it impedes airflow though the rad(s)
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Old 09-21-2011, 07:18 PM
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When is the last time that you drove your car, ended up in any amount of traffic, and didn't have your fan kick on? Fans kicking on is not a sign of overheating. Panicking when it does come on is a sign of brain overheating. The gauge on the hawk is without units, what temp is it running at? With 3 degrees per pound of pressure, you BP for water itself at 15psi is 257f. If you are under 230, it is absolutely fine, although coolant will have to be changed more often as it will degrade quicker at elevated temps. If this is a serious concern...

1. Add oil capacity, coolant capacity
2. remove rubber hose sections and replace with aluminum tubing
3. Add a surfactant. Funny, it is telling me i spelled this wrong, not so.
4. Larger oil cooler
5. Larger radiators
6. Bigger Fans


All in all, I just dont see this as an issue. But then again, I will not ride in stop and go rush hour traffic in hot weather, hot being over high 90's. I dont do it for the bike, I do it for the **** poor cooling system on my *********. I doubt Honda has it so wrong here that we need to reinvent the wheel.
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Old 09-21-2011, 07:27 PM
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Originally Posted by mikstr View Post
It would seem to me that the presence of a fan (when it is not operational) would actually hinder cooling as it impedes airflow though the rad(s)
This is a good point that I had not thought of... besides weight you're adding airflow restriction.

Also, as a note, motors are designed to run most efficiently within a certain temp range (best mpg, less wear, more power) you go higher OR lower than that and you're reducing it's potential. And air cooled motors are designed to run in the 260-270 range, so it's not like it's bad for the materials or anything... just the tolerances.
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Old 09-21-2011, 07:28 PM
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Oh yeah, I forgot to mention that in addition to my list of cooling aids my fan is on a switch so I can turn it on. NEVER rely just on the switch & no auto on. Trust me on that you will forget.

I also have my headlight on a manual switch so I can turn it off if I want to decrease battery drain (only do this in crazy bad traffic) but it is surprisingly useful to be able to turn it off.

I also run evanscooling waterless coolant. Supposedly way better than anything else & lasts forever but you do pay for it.
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Old 09-21-2011, 07:49 PM
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Engine Ice did me well this summer... also, my fans were on probably 95% of the time (100+ temps for 20-60 minutes at a time, daily commute), and if your electrical system is working properly, it can handle the power requirements. I wired my fans to kick on at 185* F, but am considering going back to stock for the winter... but now I'm just talking about my own personal irrelevent setup. I also like the color green and drawing is a hobby of mine
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Old 09-21-2011, 07:55 PM
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http://www.spondonownersclub.co.uk/i...esbikes/18.jpg

Did HRC have cooling problems? Heck, it looks like the same oil cooler.
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Old 09-21-2011, 07:59 PM
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Bet that thing didn't have to deal with stop and go traffic much though
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