Fuel Guage

[CBallman]

So I noticed this while riding this summer and never thought to bring it up till now. I get usually fill my tank up around 150 miles after a fill and here is what Ive noticed. I can usually go about 75-90 miles on the first 1/4 tank of gas (at least thats what the gauge reads) and then it starts to drop off after that and then each other 1/4 tank gets about 20 miles.....Not sure whats up with this, just wondering if anyone else has noticed this or whats going on with the bike?

 

[Smittyboy]

Nothing out of the ordinary from my experience. It really gets interesting if you run the tank lower. I fill every 220 or so, and the first half of the tank lasts into the 130's or so, the middle of the tank goes until 180 or so, then the last half drops like a rock and the last 20 or so miles I'm on the "reserve". The first half of the tank gets my hopes up "YAY 80 a gallon" lol, then reality sets in for the last half.

 

[ChevyFazer]

It's because the way the tank is shaped and the length of the float. The float doesn't quite reach the top of the tank so it reads full for quite some time, but then once it drops a little bit the gas is in one of the widest sections of the tank so it takes longer to drop, and it's not good for the pump to run it that close to empty.

 

[Reed]

The farthest that I have gone, according to fuelly is 188 miles, but my average is 141.5 miles. :BLAA:

 

[CBallman]

Thanks guys, i didn't think there was anything wrong the bike....

 

[KingY]

Its misleading!! I always think i am going to have awesome MPG untill the second half of the gauge goes to nothing in no time. I just go by miles and i know that at about ~130miles she needs another full tank

 

[Rebuilt]

That kinda makes sense because my gauge is confuseing me completly ... i filled tank right up did round 100 miles and it still read about 3/4 of a tank ... im thinking this is brilliant .. then rode about for while n it read a bit under half ...(that was getting stopped by virtually every traffic light and sunday driver around )... but then got on it n it was red lighting for almost empty ???

Filled it to just over half a tank and its reading full ???

So where is it really ... short of looking physicaly in the tank i m not sure

 

[KingY]

fill the tank, reset the trip 1, ride how you normally do untill you hit reserver ( flashing light) check how many miles you got on your trip, now you know about how many you can do before running low without having to use the gauge

 

[Dave.TX]

On mine the first bar disappears around 30 miles. Once I use 3 gallons it's into reserve. I went 190 miles last week and put just over 4 gallons in. Can't remember how far it said I was in reserve but was around 50 miles (I was getting about 45 mpg). I just know it'll show reserve with 2 gallons still left in it. The trip meter is always reset at refuel so I watch that more than anything.

Sounds like Yamaha didn't put much precision into the fuel level meter. No biggie.

 

[ChevyFazer]

Sounds like Yamaha didn't put much precision into the fuel level meter. No biggie.

Well most vehicles are like that, it's just way more noticeable on smaller capacity fuel tanks. The only way that a fuel gauge could read completely accurate through the entire range would be if the car or bike had a cube for the fuel cell, with a float arm long enough to reach all the way to the top as well as the bottom. And since most bikes have odd shaped tanks its impossible to make a 100% accurate sending unit that stays the same through the whole tank, for one most all of the tanks have disproportioned sizes, as in the top 1/4 might only hold 1/2 a gallon while the next 1/4 down might hold 1 1/2, next 1/4 1 1/4 and the bottom 3/4. Then since the tank is oddly shaped they have to make the float arm short enough as to not hit the sides and get hung up anywhere. So basically unless you want a cubical fuel tank on your bike the fuel gauge will never be 100% true on any bike. Just another reason why I have always just went by mileage on my bikes lol

 

[FinalImpact]

^^
They could count injector fire rates over time and calculate fuel burned/remaining from a fill up. :thumbup: Money wasted tho. . . . :thumbdown:

OK - a little off topic but it seems to me the cooling effect on the pump isn't possible past a 1/2 tank as its no longer submerged. So I doubt riding on low tank hurts the pump by not cooling it. Besides its only there if it sloshes up there. just sayin. . . .

 

[CBallman]

And if you absolutely want to know how much fuel is left you could put on a small rubber hose and hook it up to the bottom of the tank and run it up the side of the tank :BLAA: I have a buddy who does that to his off road bikes. Very effective in checking fuel as well as used in some instances for leveling large objects

 

[ChevyFazer]

^^
They could count injector fire rates over time and calculate fuel burned/remaining from a fill up. :thumbup: Money wasted tho. . . . :thumbdown:

OK - a little off topic but it seems to me the cooling effect on the pump isn't possible past a 1/2 tank as its no longer submerged. So I doubt riding on low tank hurts the pump by not cooling it. Besides its only there if it sloshes up there. just sayin. . . .

It's the fuel flowing through it which helps to keep things a little cooler not the fuel surrounding the pump vs sucking air. But it's not like the first time a pump sucks air it's going to instantly fail, IMHO the trash that gets sucked up in it and slowly clogging the filter hurts more than sucking air because the more trash the filter collects the harder the pump has to work.

 

[ChevyFazer]

You mentioning the injectors got me thinking, I'm sure you could just install a in-line flow meter on the main fuel line, I've personally never seen one that small, but if you could find one and hook up some sort of auxiliary display to it, that would be the ticket right there

 

[yamihoe]

Well most vehicles are like that, it's just way more noticeable on smaller capacity fuel tanks. The only way that a fuel gauge could read completely accurate through the entire range would be if the car or bike had a cube for the fuel cell, with a float arm long enough to reach all the way to the top as well as the bottom. And since most bikes have odd shaped tanks its impossible to make a 100% accurate sending unit that stays the same through the whole tank, for one most all of the tanks have disproportioned sizes, as in the top 1/4 might only hold 1/2 a gallon while the next 1/4 down might hold 1 1/2, next 1/4 1 1/4 and the bottom 3/4. Then since the tank is oddly shaped they have to make the float arm short enough as to not hit the sides and get hung up anywhere. So basically unless you want a cubical fuel tank on your bike the fuel gauge will never be 100% true on any bike. Just another reason why I have always just went by mileage on my bikes lol

my escort does the same thing as my bike, first half lasts forever, then its suddenly empty!
for my bike the reserve usually flicks on at 180miles dead on almost every time, usually 4.2ish gallons.....
now the gas gauge on my Mustang is super accurate because of what Chevy said, square fuel cell FTW! lol

 

[Rebuilt]

Ok thanks for that everyone :thumbup:... will check in the morning as have just filled tank right up ( it was bout 1/4 -1/2 full ... £16.50 later its full again ...dam petrol prices :spank: )

Done about 6 miles or as close as since filling up so will take that off the number n see :thumbup:

 

[FinalImpact]

It's the fuel flowing through it which helps to keep things a little cooler not the fuel surrounding the pump vs sucking air. But it's not like the first time a pump sucks air it's going to instantly fail, IMHO the trash that gets sucked up in it and slowly clogging the filter hurts more than sucking air because the more trash the filter collects the harder the pump has to work.

More detail:
not sure I agree but I hear you. So we agree that the electric DC motor is not being cooled by the fuel that leaves this:
Because the fuel acts as a lubricant to the pumps rotor, its the lube that extends the life and keeps the clearances proper. If left to run pushing nothing but air - that will hurt the pump because it increases the clearances making it less effective and unable to create the pressure needed at the injectors. (everything is better when lubed properly)

As for the electric motor - because the pump has no load (sucking air), its work is nil and the motor makes way less heat so its not a factor.

Rust and debris will kill it faster than anything. Thank our government for the meth and rust that follows . . .

 

[FinalImpact]

You mentioning the injectors got me thinking, I'm sure you could just install a in-line flow meter on the main fuel line, I've personally never seen one that small, but if you could find one and hook up some sort of auxiliary display to it, that would be the ticket right there

They are out there - spendy tho. . . We use them at work. The issue here is the software to correlate all the factors and use it to make a value we see at the gauge. That's where it gets complex. The ECM knows the injector duty cycle (need to track this in use; lots of data. . .) - now knowing what gear you're in and how far you traveled should get you pretty close to the amount remaining if it knew it started at an exactly full tank each time.

Think in terms of small volumes like ml/min.

 

[ChevyFazer]

I'm talking about something similar to these
http://www.google.com/m/products/ca...a=X&ei=UdNbT7-iAsfVtgfN5JiFDA&ved=0CFQQ8wIwAw

Hooked directly to the fuel line coming off the pump, it would measure the amount of fuel that flows through it, they are very simple flow meters but work flawlessly. Finding one that small on the other hand...well I don't even know if they make them, I've mainly seen them on screw pipe or PVC 1" or larger

 

[FinalImpact]

I'm talking about something similar to these
http://www.google.com/m/products/ca...a=X&ei=UdNbT7-iAsfVtgfN5JiFDA&ved=0CFQQ8wIwAw

Hooked directly to the fuel line coming off the pump, it would measure the amount of fuel that flows through it, they are very simple flow meters but work flawlessly. Finding one that small on the other hand...well I don't even know if they make them, I've mainly seen them on screw pipe or PVC 1" or larger

Ya - spendy. . .
OR: Mass Flow Controller | Digital Air Flow Meters