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Old 01-21-2013, 09:54 PM   #601
JRWooden
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A link to this "white paper" may be buried elsewhere in this thread.... but I'm posting it (again?) because I think it's a nice piece of work:

www.vfrdiscussion.com/forum/index.php?app=core&module=attach&section=attach&attach_id=8336


I read somewhere that the series style was less efficient at low RPM, than the shunt style, but I don't know if that is a true statement............
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Old 01-21-2013, 10:56 PM   #602
rockinrog
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Quote:
Originally Posted by steveWFL View Post
Just as I consider adding an 800 to my garage I see threads like this
I'm convinced that if you based your decision on which bike to by on adv threads you would be walking.
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Old 01-21-2013, 11:16 PM   #603
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Originally Posted by rockinrog View Post
I'm convinced that if you based your decision on which bike to by on adv threads you would be walking.
True
When was the last time we all sat around typing Kumbayah.

You can read a thread extolling the virtues of the next big thing after 5 or 6 "It's greats" you stop reading having got the validation you need.

Now I just read 40 pages of great info on a failure of a component on a bike I don't own...


Now where did I put that train wreck...


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Old 01-22-2013, 01:35 AM   #604
WayneC1
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GoldenTaco, the Shindengen really is the best option at this time for the 650GS, it is still a shunt regulator but faster acting and with less internal power consumption and hence less heat than a stock VR because of the FET components

The compufire sounds good but we are pushing it beyond it's stated maximums. All the reports are good though and so for the F800 in particular where stator temperatures are in serious need of lowering it is the best choice. There is another unit mentioned in the thread out of Roumania which is higher in max ratings but no one has used it as yet

In terms of reducing engine load, while we have permanent magnet alternators the ability to do so is relatively limited with the serial VR being about it other than fitting a lower output stator.

On the cars they have brush type and you can reduce voltage to the excitor coil easily and in addition to that some have a clutch arrangement which is used to disconnect the alternator under various conditions like acceleration. You will see over at bimmerforum and elsewhere people retrofitting firmware to do at least some of this. BMW's figures on fuel saving and increased engine output are a little surprising
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Old 01-22-2013, 06:36 AM   #605
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[QUOTE=WayneC1;20546741]GoldenTaco, the Shindengen really is the best option at this time for the 650GS, it is still a shunt regulator but faster acting and with less internal power consumption and hence less heat than a stock VR because of the FET components

If the worry about overheating the poorly design BMW stator is the main concern, I would point out that a shunt regulator that has "less internal power consumption" in other words for forward drop losses across the switching device (likely FET) is NOT what you want.
Why? Less drop/losses means that the total circuit series resistance is lower, this allows more current to flow thru the stator , causing MORE heating not less.

changing the regulator to one the limit total current to less than stock (400w) could help mitigate the problem of BMW's poor design....but at the expense of less out put for accessories.

Yes I too thing that useing a field regulating alternatore would be better, it would have less heating in generation, have lower loads on the engine..ie better gas milage....but it is more complex, expensive and likely heavier.

BMW has chosen the cheap simple approach but dropped the ball on stator cooling design.
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Old 01-22-2013, 06:45 AM   #606
ebrabaek
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Perhaps we will never know if the mosfet (shendigan) infact lowers or rises the stator temperature, as no one have thermocupled it. In theory, Yes I agree that if it consumes less power, the stator might work a bit harder, but I saw 0.4-0.5 volt increase in the charging voltage, which also should relieve the stator a little. It really is too bad the BMW kit is so expensive, as it seems to offer a little more cooling.
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Old 01-22-2013, 06:51 AM   #607
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Quote:
Originally Posted by ebrabaek View Post
It really is too bad the BMW kit is so expensive, as it seems to offer a little more cooling.
Based on my experience, you forget the cost fairly soon.

Old on the left; new on the right.

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Old 01-22-2013, 07:07 AM   #608
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Originally Posted by Emmbeedee View Post
Based on my experience, you forget the cost fairly soon.

Old on the left; new on the right.

I think you are right. If mine failed tomorrow, I would go the BMW route. No doubt. Thanks for the comparison.
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Old 01-22-2013, 07:37 AM   #609
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vtbob, perhaps I should have worded my response a little better, the lower internal power consumption I referred to is power consumption internal to the regulator components which means the VR itself runs cooler under normal conditions. On the 650GS in particular which is what I was asked about has poor mounting locations and the stock unit overheats as a result
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Old 01-22-2013, 07:53 AM   #610
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Originally Posted by ebrabaek View Post
I think you are right. If mine failed tomorrow, I would go the BMW route. No doubt. Thanks for the comparison.
So would you say the original design is flawed?
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Old 01-22-2013, 08:41 AM   #611
bross
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So would you say the original design is flawed?
I'd say so. This system used on bikes is cheap, easy and unfortunately prone to failure. Google just about any brand and you'll come up with stator failures. When's the last time you had an alternator fail on your car? Be interesting to see how the alternator fares on the new Triumph Tiger Explorer.

The majority of bikes run happily along without ever burning up their stator because they have OK cooling. Every once in awhile a manufacturer screws it up, the BMW F800s, my Honda CBF. Honda's fix on the gen 2 CBF was to add additional oil passages to the stator, only change they made to the motor. So far I haven't heard of any stator failures on the gen 2s and it's been almost 2 years.

Happy to be riding a Triumph now. I knew that the Street Triples had had some stator failures, but only a few and they upgraded a part for 2010, the year we bought my wife's bike. We just got a recall letter, they've redesigned the stator and to bring it in or warranty replacement, two years on. Honda Canada were no help with my CBF and just played dumb, even though it's a well documented issue.

Is that new BMW part a warranty item? Or do you have to upgrade it yourself?
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Old 01-22-2013, 10:02 AM   #612
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So would you say the original design is flawed?
I dont think that question is that easy to answer correctly. I am careful with pointing fingers, and I think that the best way to answer this is: " It is not as good as it could be" But neither is the forks.....and so forth. On a 800 cc bike a 400 watt output stator is right on the mark, as many 400cc class have about 200 watt output. many are getting 50000 miles before it toasts itself, some less than that. I would like to direct the attention to the R/R. I do believe that that is a flaw, as we have seen strings of battery failures early on. I for one had mine fail after only 11 months. They all wrote that off to a collapsed battery, But I believe that heavy over sulfating due to under volt charging is a mega catalyst in this matter. That is a flaw. All they had to do ,would be to pyt a shendigan mosfet shunt style on it... Problem solved. Then in turn..... I personally think that the stators would fare far better. Perhaps stick my neck out and say.... They would not fail. I have no proof of that, and it is just my opinion. The problem is that BMW charges a premium for this bike, and to newcomers, it has a rep that it can go around the world. And as such, The system is not up to par. So in summery..... I don't think it is flawed, but like the forks..... " what on earth were they thinking" It will be interested on what fails first..... My stator ( with the mosfet R/R) of the copufire R/R....... Hopefully neither will fail.
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Old 01-22-2013, 02:38 PM   #613
JRWooden
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The newer bikes have a different model Shindengen R/R which does regulate at a higher voltage which is good for the battery and should reduce heat load in the stator if I'm thinking about it correctly ...

Does anyone know if the new unit P/N:
SH541SC is a still an SCR-Based design or if it got upgraded to a MOSFET?



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Old 01-22-2013, 03:11 PM   #614
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Originally Posted by bross View Post
Is that new BMW part a warranty item? Or do you have to upgrade it yourself?
Chances are your warranty will run out before the stator fails. Joel Wisman reports seeing dead stators in the shop he worked at as early as 20K to as high as 50K but he's never seen any F800xx bike go more than 50K miles on the original stator. Obviously BMW figured out that the lack of oil cooling is prematurely killing stators, hence the redesign of the rotor with more openings to permit oil to cool the stator. Since there is no recall, owners are left to foot the bill when the stator fails beyond the warranty.
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Old 01-22-2013, 03:19 PM   #615
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Originally Posted by ebrabaek View Post
like the forks..... " what on earth were they thinking" .
the forks were built to a budget; they are crap on the road and crap off road.. but the bean counters dictated non adjustable budget forks and I didn't mind them. The rotor for the stator on the other hand is the result of a poor design and poorer prototype testing.. They can easily simulate 50K miles by running the engine continuously to see what breaks, and maybe they did . at any rate, making a few more holes in the rotor shouldn't change the overall cost, so I'm inclined to think the original design was flawed, and is basically a ticking time bomb in every F800xx. At least on this forum, we have figured it out, know the symptoms and the fix.
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