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Aux Fuel Tank

Discussion in 'Stelvio Chat & Tech' started by Ray R, Dec 20, 2009.

  1. Ray R

    Ray R Cruisin' Guzzisti

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    I've decided my Stelvio needs an auxiliary fuel cell. I'm tired of the low fuel light coming on at around 120-130 miles. I'm thinking a minimum of 4 gallons, but I've seen tanks that would fit which hold 7 gallons. I've reviewed the setup BigTex did on his bike, and I think he did a great job. I'll likely do something similar, but I do not possess the custom fabrication skills he has. So mine will be developed with more off the shelf components.

    First, I'll start with my bike set up basically like a NTX, more or less.
     

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  2. Ray R

    Ray R Cruisin' Guzzisti

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    Next, I've ordered a new pillion seat that I'll use as the base for the tank. I'll simply be removing the cover and foam. I checked into having something custom fabricated, and the cost would be more than the $116 for a new seat from the dealer. I think the plastic seat pan is certainly strong enough to hold 4-7 gallons of fuel. At 6.5lbs per gallon, that'd be somewhere in the range of 25-50lbs plus the weight of the tank, which I assume will end up being plastic or aluminum. Plus, I know the stock pan it will fit well, and I'll be able to easily remove it and use the stock passenger pillion seat for those times when my darling wife wants to go for a ride.
    Here's a shot of the pan and the location.
     

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  3. Ray R

    Ray R Cruisin' Guzzisti

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    As for getting the fuel from the auxiliary tank to the main tank, I'm going to try something a bit more unconventional. I used to own a BMW G650 XMoto that I bought an aux tank for. On that setup, you connected the fuel line from the new tank to the existing tank's air breather. As fuel was used in the main tank, it would automatically siphon fuel from the aux tank to the stock one. The breather to air was on the aux tank.

    On the Stelvio, when I removed the charcoal canister, I plugged the fitting at the fuel filler neck where the canister vent line went. Since then, I've noticed I get a real vacuum in the tank, sometimes to the point where it's difficult to open the gas cap for refueling. I planned to fix that at some point this winter, but I'm thinking of using this vacuum to siphon fuel from the aux tank to the main tank using that fitting, much like what worked on the XMoto. I'll then use the aux tank to vent to air.

    If it doesn't work, I'm really not out anything. I'll just add a fuel pump if I need to.

    You all see any issues with my plan so far?

    At this point, I've ordered the new seat pan and am waiting for it to arrive at the dealer. Stay tuned.......
     
  4. Ray R

    Ray R Cruisin' Guzzisti

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    One more note on this project. So far, I've found two tank providers that seem promising. One is www.tourtank.com and the other is www.sampson-sporttouring.com. Do any of you have experience with these? Any others you'd recommend?
     
  5. Mike.C

    Mike.C GT Reference

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    Hey Ray, Why not have a custom one made to fit in the space between the RHS pannier and the frame?
     
  6. Ray R

    Ray R Cruisin' Guzzisti

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    Good suggestion for sure as it would keep the weight lower than a tank in the pillion position. But, in my case, the Givi luggage brackets are not really suited to support an extra 25-50lbs. That, and I'm not sure that area is large enough for 4-7 gallons. Also, 25-50lbs is too heavy, in my opinion, and would unbalance the bike.

    That said, I went out and took some measurements and a closer look at that location's potential. Based on my measurements, I think the best you could do is 2-3 gallons there. That's based on the volume calculator on sampson-sporttouring's website. I think there is some potential for mounting a tank on the back side of the stock bag mounts. But it would be 100% custom fabrication, and I'm shooting for using off-the-shelf components.
     
  7. Mike.C

    Mike.C GT Reference

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    I hear what your saying about weight, but I have seen plenty of blokes with DR650's and fuel strapped on to kingdom come riding like maniacs in desert sand, doesn't seem to be an issue in practice.

    Rotopax might have something off the shelf that fits WEB SITE HERE

    I'm watching your progress with interest, as for Oz the Stelvio range is hopeless and I will have to engineer a solution - for comfort and safety touring outback Oz 600km range is a must.
     
  8. RokonRon

    RokonRon Tuned and Synch'ed

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    Interesting idea Ray, I may have to give that a try. That would give pretty seamless operation, the fuel gauge would read full until all the fuel was used up from the aux tank then operate normally over the final 150 miles or so.

    The only drawback I can see is that if your aux tank is higher than the main tank, then when the aux tank is full and you open the main tank cap the main tank would overflow. It looks like my aux tank set up hold less than two gallon above the main tank full level, so it would not be much of a problem after about 80 miles or so. I would just have to remember to fill the main tank first and close the cap before I fill the aux tank.

    Ron
     
  9. Ray R

    Ray R Cruisin' Guzzisti

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    Exactly my thoughts. And yes, part of the aux tank would indeed be higher than the main tank. So your concerns are valid. But as long as you stay aware of what's full and what's not, I think it would work. And I don't see any drawback in trying.

    The one thing I haven't mentioned yet is a metal aux tank will need a ground wire. I'm not sure of the physics of it. But everything I've read says you need one. And that G650 tank had one too. Probably due to a buildup of static electricity if you don't have one, and the subsequent explosion when that static sparks. :woohoo:
     
  10. Ray1150

    Ray1150 Cruisin' Guzzisti GT Famiglia

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    Have you looked into scrapping the tank and plastics and having somethong fabricated Ray?
    I would certainly be very interested as I bought my MG specifically for 2 up touring and although we havn't done much mileage yet I've already filled up a couple of times 17 litres +. I get a horrible feeling I'm going to left high and dry somewhere.
     
  11. kmartin

    kmartin Cruisin' Guzzisti

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    I'd be a little concerned that any seepage around the main gas cap would result in paint deterioration. I've found a little already, and have made it a point not to try to completely fill the tank. I usually quit after the fill nozzle shuts off the first time.
     
  12. Ray R

    Ray R Cruisin' Guzzisti

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    I have not, mostly because of the way the plastics all integrate with each other. Those pieces around the tank are part of the fairing assembly. I just don't see a clean way to make that work without screwing up the lines of the bike.

    But you are correct. There is a lot of wasted space there, with the glove box and plastics. I think it'd be relatively easy to mount 7-9 gallons there. But I think in doing so, you'd be redesigning the entire fairing and tank assembly. Too much $$$ and, again, can't be done with off-the-shelf parts.
     
  13. RokonRon

    RokonRon Tuned and Synch'ed

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    We'll soon find out. :D I hooked up the aux tank to the main tank this morning. Next step is to fill them up with gas and see what happens. I've got a shut off on the aux tank just in case. I have also noticed the paint deteriorating in the space under the main tank cap due to over filling, so I'll watch closely for seeps. Maybe an extra rubber gasket under the cap if all doesn't go well?

    Ron
     
  14. Ray R

    Ray R Cruisin' Guzzisti

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    Excellent! I look forward to your results! How did you plumb it into the main tank? Did you use the vent port?
     
  15. Bob Bernstein

    Bob Bernstein Cruisin' Guzzisti

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    Hey Ron, I am looking at the picture of your bike and wondering what kind of attachment point you use under your rear bag? It looks like it replaces the passenger seat. Does that interfere with the battery?
     
  16. Ray R

    Ray R Cruisin' Guzzisti

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    That "rear bag" is his aux tank! Good disguise, huh? :)

    If you look at www.tourtank.com, you can see the bag/cover in the accessory section.
     
  17. RokonRon

    RokonRon Tuned and Synch'ed

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    Ray,

    I ran a 5/16" line to the top of the main tank in front of the gas cap, I didn't think the vent line was big enough for a transfer pump.

    Progress report: Well, I went to get a can of gas and left the aux tank on, when I got back the main tank was fuller and the aux tank was lower, not a good thing, the main tank wasn't holding pressure. If the aux tank had had enough fuel at some point it would have over filled the main tank. I checked out the cap gasket and it looked like it was sealing OK. I think the problem is the seal between the filler neck and the cap assembly. Its held together with four screws, but the nuts are brass inserts in plastic and I could feel them slip in the plastic. I put a bunch of grease on the mateing surfaces to see if I could get it to seal and reassembled. I filled up the aux tank and filled the main tank to the top of the fuel pump assembly. After closing the cap and turning on the aux tank I let it set for for about 1 1/2 hours. When I came back I shut off the aux tank valve and opened the main tank and was greeted with a 'whoosh', that's a good sign. When I checked the levels they were the same as they were when I started the test, alright!

    Now I need to get some good fuel resistant gasket sealer to replace the grease for a more permanent fix. If that doesn't work I guess I'll have to look into making a metal ring to replace the brass inserts, but I think I'll be able to get it to seal with the fuel resistant gasket sealer. I probably wont get out to check the fuel transfer until after Christmas, but I'll let you guys know how it goes.

    Here's a bigger picture of my bike:

    Ron
     

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  18. RokonRon

    RokonRon Tuned and Synch'ed

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    Well, I guess it's time for an update. I have been messing around with the gas cap and I don't think it is up to the task of holding the pressure exerted by a full aux tank. I used gasket sealer between the rubber filler tube and the gas cap assembly, when I filled up the aux tank and let it set for 5 hours, the level had dropped about an inch. Something was leaking air. I put grease on the gas cap seal and tried it again, this time the level dropped about a quarter of an inch. Without a lot of work getting the gas cap to seal I don't think the cap is up to the task. Even if the gas cap can be made to hold the pressure, I don't think I'd trust it over the long run. If something get under the seal or the gasket gets old you could wake up to find the Stelvio sitting in a two gallon poddle of gasoline, not good.

    If the vacuum transfer is going to work I would think some kind of a positive shut off in the hose between the two tanks will be needed to contain the fuel in the aux tank until its level drops below the level of the main tank cap. The shut off will have to be turned on when the engine is running since the main tank vent will be disabled to create the vacuum to transfer fuel. Maybe a fuel compatable solenoid valve powered by a switched 12v supply?

    What do you guys think? Any ideas?

    Ron
     
  19. Ray R

    Ray R Cruisin' Guzzisti

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    Ron, I appreciate the work and testing you've done so far. No doubt you've saved me some significant trouble and effort. Thank you. I had been thinking more about this since you had the original dilemma with the leaking cap. I don't think sealing the cap would be a reliable long term solution. Instead I'm thinking maybe the aux tank could to be designed with the supply line coming out of the TOP of the tank instead of the bottom. And the supply line would extend inside the tank to the bottom. That way gravity wouldn't play a part in the flow of fuel. Rather it would be by siphon only (or pump if necessary). And to be certain, I'd add a shut-off valve between the aux tank and main tank for use when the bike wasn't running. If I remember correctly, that's the way the G650 aux tank was designed, except without the shutoff valve. The details of that tank are here:

    http://www.hotrodwelding.nl/product.php?id=3

    and here:

    http://www.advrider.com/forums/showthre ... 63&page=12
     
  20. Ray R

    Ray R Cruisin' Guzzisti

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    I thought it was time for a quick update.

    It turns out the folks in Italy took some time off for the holidays. As such, my new pillion seat is still on order. It may be another week or two before I see it. In the mean time, enjoy your ride!
     

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