FJR stock tank, trapped fuel & max distance

I'm usually at a gas station before the "F" shows on the fuel gauge but not always. One thing I don't have a good handle on is the amount of fuel I can "safely" assume is remaining in the tank when I see it switch over. Several interesting characteristics add noise to this calculation. First, it doesn't always seem to latch over at the same place. Run the bike on the stand for a few and it will go into reserve and only sometimes come out after riding for a bit. You'll definitely be back in it soon though. Second is the idea of trapped (unusable) fuel in the tank. In the aircraft design business there is always an amount of fuel in the tanks that you will never be able to get into the engine. This weight is parasitic and is carefully calculated using our CAD tools and verified in the fuel barn. There will be some amount of the total capacity in the FJR tank that won't get into the feed system and I don't know what that is for the stock (in my case Gen II) tank. So, one way to tell for sure is to run her around the block over and again until she starves then fill her up and do the calculations. I haven't conducted this test yet but maybe some of you have either by design or by accident.

Anyway, I'm curious about member's experiences in this area.

Cheers,

W2

I've only had my FJR for 4 months but I have found that I can go usually about 50 miles or so on "F". This usually shows about 225-240 miles on the tankful, requiring 5.7 or so gals to refill. This of course will vary with driving conditions, but I usually test a new bike for range when I get it so I know how far I can push it. Of course the rule "get gas when you can" still always applies.

My experiences sound pretty close to 07fjrTom's.

The gauge usually starts to show the fuel warning at about 190 miles. I usually let it go until it counts to about 35-50. That usually ends up then taking 5.1-5.4 gallons.

I keep it on the side stand during fueling, and bring the fuel level up so that it is just touching the metalwork that the nozzle fits into. There are a couple of gas stations that I avoid, because they have noticeably non-level concrete pads. (Still fill the wife's van up there though.)

I did push it once...it started to hesitate a bit when the counter was up to about 70. Rocking the bike left and right every once in a while kept it running to the station.

Wee Willy said:

....the amount of fuel I can "safely" assume is remaining in the tank when I see it switch over. ...trapped (unusable) fuel in the tank.

Anyway, I'm curious about member's experiences in this area.

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07fjrTom said:

...I can go usually about 50 miles or so on "F". ...about 225-240 miles ... requiring 5.7 or so gals

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Allnight said:

...fuel warning at about 190 miles. I usually let it go until it counts to about 35-50. That usually ends up then taking 5.1-5.4 gallons.

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Bbbut..., from the "Bin-O-Facts" (fuel capacity): 6.61 US Gal (1.45 US Gal reserve)

Is there about 1 (one) gallon of unusable (parasitic) fuel always carried in the FJR's tank -- that's not accessable for use...?

Rather than a full gallon being that parasitic gallon, I'd label it more like "I'm not allowed to violate that except in times of war" (thinking of Hunt For Red October).

You *can* go farther and need to put more in, however, I'm unwilling to risk getting stuck and so I don't let it get that far down.

It would be an interesting experiment to try, if you have someone that can follow you with 7 gallons of fuel, so that when the engine finally can't get any more fuel that you can see how much the tank takes. That also assumes that these engines aren't direct-injection, as I believe direct-injection systems are damaged when there isn't enough fuel to operate them correctly (but that could be rumor/fear-mongering, I'm not that technical).

charismaticmegafauna said:

Bbbut..., from the "Bin-O-Facts" (fuel capacity): 6.61 US Gal (1.45 US Gal reserve)
Is there about 1 (one) gallon of unusable (parasitic) fuel always carried in the FJR's tank -- that's not accessable for use...?

Click to expand...

My point exactly!! That sounds like quite a bit. My gen 2 is averaging 39.33 mpg (per the odo) today after 13 months and 12.7k miles. With 6.61 gal tank capacity, I am theoretically capable of ~260 miles. I usually go over to "F" at around 190 miles (or 4.83 gal) as well. This calculation says I have another 70 miles on reserve (or 1.78 gals) ONLY IF I CAN GET IT ALL TO FEED. I've never pushed it past about 20 on reserve and began to feel nervous until I sighted the station because I had no idea where the cliff was (basically, what the trapped fuel value is).

And one other question...is the 6.61 gal the total internal volume (gas to the fill lip) or to the bottom of the ulage neck?

And if the 1.45 gal reserve is ROM correct, then that might indicate that 1.78 gal less 1.45 gal is the trapped value: about 0.33 gal worth almost 13 additional miles and that sounds like a reasonable number.

EDIT: so with 1.45 gals & 39.33 mpg, I should get gas by about 57 miles after the "F" appears. Anyone else have a different story?

Cheers,

W2

My current FJR only has about 1.25 gallons once the low fuel miles start counting. My other FJR's had 1.5 gallons so found out the hard way on a deserted stretch of I-40 near the New Mexico/Texas border. :dribble: I usually lookl at the AVG MPG on the gauge to see what I have been getting and calculate how far I can go from that.

I usually fill-up with over 6 gallons with the bike held upright or on the center stand and I top it off to get as much as I can. Really cuts down how much you can put in with it on the side stand. Side stand also really throws off the fuel level, panicked on that one time too. :glare: I always park the bike on the center stand so it threw me off.

But actual mileage really varies from rider-to-rider and really depends on how the bike is setup and on how you ride.

Brian

QUOTE (Big-B @ Apr 22 2010, 10:30 AM) <{POST_SNAPBACK}>
...so found out the hard way on a deserted stretch of I-40 near the New Mexico/Texas border. :dribble: ...
Had a similar experience once on I-10. It was my first cross-country trip and I was 18 years old. About $100 cash and my dad's shell card were all the finances I had when I left California heading for Florida then Kentucky to go to school. Riding a Honda 550-4 I was used to seeing a gas station every 5 miles or so along the interstate. But this part of Louisiana just had roads that intersected and ran N/S with nothing at the interchange except stop signs. Turns out I would have needed to go N or S along one of these 5 or 10 miles to some small town with a weird name to fill up at a Conoco. So not knowing what lay down these roads or what was ahead, I trusted the interstate system and kept riding. After going into reserve and beginning to worry I came to a bridge over the swamp that must have been 20 miles long if it was a foot. I ran out of gas right in the middle of that thing. Had shoulder length hair & a California tag at the time. I was passed up by no less than 4 LHP cars even as I was waving for help. I swear they were just doing laps to get a laugh. Pushed that baby a couple of miles back the way I'd come (didn't know what was ahead so didn't go that way) until some guy from Texas in a long white caddy with longhorns on the front pulled up, got out and gave me some gas from a setup he had in his trunk. I offered him $20 and he refused. He was about 4'6" and wore a wide-brimmed hat almost as tall as he was. Had really nice boots out of some critter's hide, a dish plate for a belt buckle and 100% original Texas drawl. He was a hoot.

He followed me to the next gas station to make sure I didn't end up stuck then took off into history with a wild toot on the horn (remember the General Lee? Something like that.) and a big Texas grin.

The places we've been...hadn't thought about that one for awhile.

Here's to living the good life. Cheers,

W2

Here's some numbers from my 07 with PC-III running stock map and crappy winter blend fuel (average 35 mpg):

Miles on reserve ------- gallons pumped to fill tank to bottom of tank insert with bike on centerstand

39---------------------------- 5.933

32.2--------------------------- 5.642

45.8-----------------------------6.362----------------bike was stumbling

52-------------------------------6.275----------------bike was stumbling

QUOTE (Big-B @ Apr 22 2010, 01:30 PM) <{POST_SNAPBACK}>
I usually fill-up with over 6 gallons with the bike held upright or on the center stand and I top it off to get as much as I can. Really cuts down how much you can put in with it on the side stand.
Really?

Maybe the 2nd gens are different then. If I fill mine on the side stand (I usually do, while still sitting on the bike) and I squeeze in as much as I can till the gas is building up the filler neck (which I also do, just because I'm AR) and then I tip the bike vertical, I can't get much more than a few ounces of fuel in there, if that.

Excellent Harald...that's some of what we're looking for. So here's the data plotted up and regressed (LSQ):



The last point looks like it might be a sporto as the other three look almost linear. I decided to include it in the regression anyway as I can't find any other good reason to chuck it. Besides, the slope is the inverse of mpg and it looks a bit low (too steep in this plot). The intercept for Harald's case is ~4.55 gal. That's where he would tend to statistically go onto reserve. We don't know what mileage his rig tends to run at, but the slope gives us an idea. Inverting the slope gives us 28.16 mpg which seems low unless Harald really drives it hard and/or heavy...or just drives up hill all the time . Don't know.

EDIT: maybe the third point is a sporto...dropping it and using the remaining three gives us an intercept of 4.66 gal to reserve (better) and a 32.0 mpg (better too). so that third point should probably be dropped as it doesn't seem to match the general experience of other riders.

We would need more data to get a definitive look. What kind of mileage do you generally get Harald? And confirming that you have a standard tank size (gen 1 or 2?).

W2

I shoot for 220 miles at "normal" highway speeds (Usually 75-80 mph), and generally put in ~~5.5 gallons or so. That's close enough for me as I don't like to "push it" more than that. When I get the aux tank, then on to more range...

Note, too, from Harald's data that the bike was "stumbling" at around an average of 6.3 gals down. This fits with the earlier idea that 0.33 gals is "unusable" or trapped in the stock tank.

Cheers,

W2

Wee Willy said:

Note, too, from Harald's data that the bike was "stumbling" at around an average of 6.3 gals down. This fits with the earlier idea that 0.33 gals is "unusable" or trapped in the stock tank.

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Or like someone else mentioned, maybe that is in the tank's headspace? Just because they say in the manual that the tank is 6.61 gallons doesn't mean you can actually put 6.61 gallons in there. Only way to know for sure would be to completely empty the tank and then see how much you can physically put in there.

Wee Willy said:

This fits with the earlier idea that 0.33 gals is "unusable" or trapped in the stock tank.

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That will also vary depending on the bend of the float in the tank that seems to vary on bikes (and discussed many times), accuracy of the gauge, manufacturing tolerances, whether they lean to one side and splash fuel around as it empties, etc.

I filled on a Gen 1 with 6.33 once (also posted many times) to the tippy-top leaving a calculated reserve of 0.27 gallons without stumbling.

However, I don't think ANYBODY has actually ever drained a tank and actually measured it since I've been on this forum (posted zero times). Until somebody does and documents it--it's all speculation and reversion to published specs.

Also, unless one likes to flirt with running out of gas and the possibly attendant issues of air in the line, dry fuel pump, and other unforeseen complications...I find it far easier and to just get gas when it starts flashing.

Ignacio said:

However, I don't think ANYBODY has actually ever drained a tank and actually measured it since I've been on this forum (posted zero times). Until somebody does and documents it--it's all speculation and reversion to published specs.

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Of course a direct measurement or two will tell quite a bit. But even those measurements will have their own error. But there's one really marvelous thing about statistics and data. Get enough information, even noisy data (data with a lot of error) and you can zero in on the driving details with amazing accuracy. Now, that's just a plug for the mathematics, not the story provided by the 4 data points above. However, if we could get 10 or 20 decent points we would have a very good peek into what the stock tanks can do. Hard part in some situations is just getting the data though. And that's why we're here.

Cheers,

W2

I have put 6.51 gallons in my '03, that was after it started stumbling and with a quick side-to-side motion you can get enough in the fuel pump to make it a few more miles. The range depends on a lot of factors including, application of scenery fast forward rheostat, temperature, altitude, humidity, tire pressure, windshield position, saddlebag/or not, rider aerodynamics, state of tune of the engine, etc. The worst range I've seen was 120 miles to empty, and by that I mean pumping in 6.5 gallons and no, the bike was running just fine

Grady

I went 265 miles last sat before the flashing started, being ya get 60 or so after that I could have went 325. Of course I was ride'n with a 1100 shadow & we did a lot of 50 to 60mph ride'n. Still impressive as he gassed up 3 times.

I've found that it's organic in nature (v mechanical) it's a dynamic that depends on a lot of variables. Therefore hard/fast/absolute numbers are unobtainable and, if collected, are often unreliable. It all depends on fuel type, operator manipulation of the throttle (independent from tops speed), cruising & top speed, RH, weather, wind (head/tail/cross), and a lot more.

If in a city/town (local commuting) you can risk riding closer to the ragged edge than if our in BFE. In the first case I can realibly go (at least) 240 miles on a tank and still not run out. In the other case, I'm usually planning for a stop at or before 200 miles.

As far as WHEN the indicator flips to F, that's also dependent on the way the float was installed in the bike and varies from bike to bike.