What does each bar on the fuel gauge represent? Miles or fractions of gas?

[_imp]

According to Honda, the CB1100 fuel guage display is based on a complex formula that includes such factors as the current price of sushi-grade tuna, the riders blood pressure average since starting the bike, and the phase of the Moon.

They also stated that any correlation between the display and the quantity of fuel in the tank is purely coincidental.

Yeah I can see that.Because the Tsunami happened back in
2011 way before production.And that one can't jump to
conclusion and blame on Godzilla making a come back due to
high water marks.

[kenfyoozed_imp]

Does gas pool on one side of the tank away from the pump? This may be why the last bar flashes but only takes 2.? Gals to top off. When it should be more as the light should come on .9 gals left.


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[the Ferret]

Well maybe one of the guys thats pulled a tank can comment but from looking at a parts microfiche, it appears the pump with float assy sits dead center on the bottom at the rear of the tank, and the float arm aims down to the bottom of the tank and maybe rises vertically? ( btw check out the price of a fuel filter..yikes...)

http://www.hondapartshouse.com/oemparts/...-fuel-pump

[Lord Popgun]

Email them to me, i'm sure many would be interested in seeing them. I would.

ferret, I'll pull them out of my camera and get them to you tonight.

They aren't on my phone or I'd send them now!

Well maybe one of the guys thats pulled a tank can comment but from looking at a parts microfiche, it appears the pump with float assy sits dead center on the bottom at the rear of the tank, and the float arm aims down to the bottom of the tank and maybe rises vertically? ( btw check out the price of a fuel filter..yikes...)

http://www.hondapartshouse.com/oemparts/...-fuel-pump

When I pulled my tank, I drained it first while the bike was on the center stand. Pretty much, all of it drained out, except for a couple ounces. After I got the pump out I looked inside the tank and the fuel won't pool on one side. Well, unless you are leaning

[AzBob_imp]

You guys are only looking at half the picture... the sender. The ECU can do whatever it wants with that signal, and it does. I have read that Americans have a weird thing about gas gauges in that they don't like seeing the gauge tick down immediately after refueling, and so most vehicle manufacturers fudge the gauge so that the first tick stays there longer than any of the others. On my CB (and my Mazda), the first tick is worth more than any of the others, and it gets progressively less as it goes down (my Mazda is especially bad, the first block is worth about 125miles, and the rest average 20).

The first bar for me is worth about .8 gallons and the flashing red bar is worth somewhere north of 1 gallon. The in-between ones, I have no idea, and don't care. You can get about 200 miles from a tank if you try. I have begun refueling at around 175 miles, and have somewhere between .3 and .5 gallon left when doing so. I usually get about 50 mpg.

[Gingersdaddy_imp]

I agree, its just a gauge and a reference point and can very somewhat even on identical bikes.

[flynrider]

The bars on my fuel gauge disappear relatively reproducible with each 50 km.

Hmmm doing the conversion 50 km equals 31 miles 120.66 yards ..interesting

Hmmm doing the conversion 50 km equals 31 miles 120.66 yards ..interesting
If you take the fuel pump out of the tank and look at the assembly, you will see the float arm is attached to a wiper that sweeps across a small circuit card with contacts etched onto it. As the fuel level decreases, the float drops and the wiper moves to a different contact. The contacts are equally spaced (if I remember correctly). The float drop is not linear due to the shape of the tank so our bars do not work as we would like.

(I have pictures of it, but still don't really know how to post them. If anybody is that interested, I can email them to ferret and he can post them.)

Being an electronics tech. (but not an engineer) my thought was they could have spaced the contacts differently or maybe I could trim them some to be narrower or whatever, and maybe adjust the bar operation. BUT, too much work and I really don't feel like messing with that.

I think Honda could have done this, but, that adds cost in design and manufacturing. Or maybe they just didn't think of it.

Therein lies the problem. Had Honda wanted to make the fuel gauge display linear, they could have adjusted the spacing between the contacts to account for the tank shape. Doing so would have resulted in each block representing an equal amount of gas.

I'm sure there were cost and manufacturing issues that went into the decision. Unless the gauge sender's part number is unique to the CB1100, it wouldn't be feasible to customize it to the CB1100's tank shape and volume.

Realistically, were talking about a bike fuel gauge. I'm satisfied that when all bars are showing, I've got plenty of gas. When few bars are showing, I have less gas. The important part is that the flashing bar warning is accurate (at least on my bike).

This is the first bike I've owned with a fuel gauge (and without a petcock). I was a bit apprehensive about it at first, but practically speaking, I manage my fuel pretty much the same as on previous bikes.

[Deanohh_imp]

The fuel sender depends on a simple float at the liquid surface. The shape if the tank itself has a huge effect on how far the surface of the liquid falls as fuel is used up.

on the wiring diagram, the sending unit signal seems to bypass the ecu and go directly to the fuel meter.

also the linearity of the gage is affected by the float arm geometry as the angle of the arm changes as it drops with the fuel level.

[ingobohn_imp]

No you are not overthinking, the angle of the gas in the tank, especially when it gets low, definitely has an effect on the float arm. While out riding I also have had the red light start flashing only to have it go out again for a few miles, depending on how/where I am riding. If the sensor is in the back of the tank, going down a big hill would have to affect it if the fuel is low enough.

I think when I paged through the CB 1100's repair manual, I read that the float arm reads every 15 sec the fuel level inside the tank. But I am not sure whether this means that the float arm reads really every 15 seconds one time and sends the result to the ECU or reads the fuel level all the time but builds a 15 sec average which is reported to the ECU.
The second way would smooth out some outliers of level measuring (driving steep up or down, accelerating/decelerating massively).

[the Ferret]

ok popgun sent me the pics from his fuel pump/sending unit removal. I am going to post 3 of them

Pic 1 shows where the fuel pump/sending unit is located in the tank looking from the bottom dead center in the middle rear
[url=http://smg.photobucket.com/user/theferret111/media/sendingunit_zpsbddeca05.jpg.html]

2nd pic shows fuel pump the fuel pump/sending unit removed and the float arm

[url=http://smg.photobucket.com/user/theferret111/media/sendingunit1_zps5341a6ba.jpg.html]

3rd pic shows the contacts on the sending unit for the fuel bars (individual vertical dark gray strips) and the silver arm for the float. Notice they appear to be evenly spaced.

[url=http://smg.photobucket.com/user/theferret111/media/sendingunit2_zps4a6e8c21.jpg.html]