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Fuel tank size claims

Discussion in 'General Motorcycling Discussion' started by CamHornet, Oct 26, 2006.

  1. This is something that annoys me quite a bit; kind of like hard-drive manufacturers' claims of "160 GB" when in reality the size is 160,000,000,000 bytes. But that's another issue.

    I have a problem with the unusable part of the tank. It mysteriously holds an extra 2 litres that I cannot find. When I hit reserve I usually ride to a petrol station fairly soon. Although I've got a tank with a supposed capacity of 13+3 litres, I only ever need to fill up 11 litres!

    I'm a little hesitant to run it dry on reserve, but how many of you experience this problem?

    Do the manufacturer’s claims of the size of the fuel tank include all the fuel lines, carbies, and cylinder capacity???

    Other than that, I'm a little confused. Thermal expansion with warm fuel doesn't differentiate by 2/13!

    I'm sure it doesn't matter much with a tourer, but my Hornet (for short city runs) only gets 160 km before reserve! (220 for highway).

    Anyone else have a major discrepancy with their tank sizes?
  2. Jeez, Cam, I don't know how you ride, but I get at least 220 round town and up as high as 235 on a trip (unless I fang it in the twisties!) The worst I've EVER seen is 190 after a brisk run between Orbost and Eden (before running onto reserve, I mean)

    But I agree about mysterious capacities; I think the Hornet tank is supposed to be 16 litres??? Even after running for quite a while on reserve I've never seen close to that on fill-up :?:
  3. How much do you fill it up? There's full and there's full. ;)

    My bike usually fills with about 16L if I run it into reserve, and I think it's a claimed 18L tank - so about on the money. Mind you, that's only if I fill it right up - and if I do fill it up I need to ride it for a bit after filling up to prevent overflow. When the tank is full if I park the bike so it has a decent 'lean' to it, then a full tank will run into the overflow and dribble onto the ground.

    Solution is obviously to not fill it all the way if I'm stopping shortly.
  4. Yeah my bike claims an 18L tank and once I filled the bike after running WAY into reserve and I ended up putting 17.6L in, so I'm thinking that my specs are kinda spot on. :grin:
  5. The GTR has been very consistent, I always get right around 25 litres in after I switch to reserve (on a claimed 28.5 litre tank).
    Maybe the Hornets' have a broad. flat tank top, which is sensitive to angle and trapping air in the top? The Z would do that, one day you'd get 15 litres in, next time 13 litrew or so.....

    Regards, Andrew.
  6. I think the other Hornet problem is you can't fill it up completely because you don't have a centre-stand......
  7. It could be even more mysterious than you think. You are assuming that the 'litre' you get at the pump is actually a litre. I often fill jerry cans with calibration marks molded into them, and my 20ltr cans almost always take 20.5 to 21 litres as indicated at the pump.
  8. I like to ride hard :cool:

    No, seriously, I'm getting the bike tuned at Tash's recommended dyno-guy on Wednesday next week. Maybe my Micron exhaust is throwing it out quite a bit.
  9. Funny you should say that! I have two 25 litre plastic drums I carry various fuels (diesel, petrol, premix 2 stroke) in, and noticed this too.
    I actually measured the drums up to a moulded ridge by using a 1 litre kitchen measuring cup and got 24 litres. I always got over 24 litres of fuel in them! I never tried it with Avgas, would be interesting to compare to see if the bowser was accurate in that slightly more critical application.
    It makes sense the pumps would be set up to err in the service stations favour, but :evil: :evil: :evil: :evil:

    Regards, Andrew.
  10. I dont think I'd be putting to much faith in a chinese jerry can.
    Just my 2 bob's worth
  11. Ah-hah, but my situation is the other way around! If my tank is accurate, then that means that the petrol stations are undervaluing their gauges by 15% ish

    Now in these "low-margin for the bowser operator" times, this would be a significant loss!
  12. And those molded marks are how accurate? And for what?
    Density of petrol varies with temp more than it does for say water. If the level of accuracy of the molded marks is like those on oil containers its only a guide and therefore indicative only.

    i've actually found the stated fuel capacity for my current 98 VFR and previous ZZR to be consistant with my experience.
  13. Neither would I. That's why I'm talking about certified and calibrated graphite impregnated anti-static aviation fuel cans imported from Germany at $160 a pop.

    No, I said it may be more mysterious than you think i.e the tank error could be even greater than you think.

    EDIT - Posts combined
  14. Owned!!
  15. On my Beemer the tank pretty much holds what they claim. I have a 20 litre tank, last week I had 4km showing on the dial until empty, filled it right up and it took 20.65 litres. What does this mean in reality..5 full trips to work before I have to fill it up.
  16. Yep. I'm supposed to have a 20 litre tank. After running it out of petrol, twice, on one tank (putt, putt, stop . . . slosh tank . . . putt, putt, stop . . . roll into a petrol station) I was only able to fill 18.81 litres.

    To make matters worse, the "fuel used" as reported by the guage is always about 15% less than the fuel volume I refill. Even worse, the petrol warning light comes on when there is about 10 litres left in the tank, or at about 160 Km, at which time the fuel guage stop showing anything. Just flashing dashes. This is a known problem with the Multistrada, apparently fixed in the 2007 model. The joys of Ducati. :?

    I get 305 Km on a completely full to empty tank. Tested twice. :shock:

    Sounds to me like your reserve is actually set at about 5 or 6 litres, and you may only be able to fill to about 15 litres of the 16 litres capacity. You should strap a 3 litre fuel tank on the back, and ride until it stops. You may be surprised how far it will go. Then fill up soon after topping up with the 3 litres, and see what you can get into it.

    My old Honda used to just keep on going forever. :grin:
  17. roderick speaketh the truth. The only better way is to buy a new bike out of the crate (hehe) or drain the tank and then fill it yourself.

    To be honest, i've not found a bike tank I couldn't fill with the quoted figure once it's been drained and dried for servicing.
  18. my fuel tanks 18 ltrs and i filled up 18.2 litres once :-k
  19. Hey guys,

    Do you remember science class at school?
    Do you remember when you wanted to get an accurate measurment of liquid you would have to use a tall small diameter cylinder to measure rather than the larger diameter beaker?
    What I am getting at is the larger the diameter/bigger suface area of the base of the volume, the more inaccurate it is for measuring. It is like any measuring device there is alway some inaccuracy, thus measuring devices normally will have a tolerance marked on them.

    The only way I can think of to give you a more accurate measurement of liquid is to have a flow rate in filling wired up to some electronics that totals up the figure. ie flowrate would sense litres per minute and than what is measure is than added up .
  20. My BMW tank is reasonably accurate I think, but in order to get the last litre in I did a little mod that I learned from a bloke when I had my Honda Valkyrie and have since done on every bike I owned.

    I get a very pointy leather punch and punch a small hole at the very top of that stupid tube in the filler neck, the one that makes it almost impossible to get the last litre or so in. Do not drill it though, or you could get bits of steel in your fuel. I can now fill right up to the top without any hassle at all.