Extremely low MPG

[VAcracker]

I think I might be missing something but my take on things, is some folks are making a big to do out unnecessarily.

Gauges are guides and we’re not dealing with super extreme precision requirements. If you need Precision have NASA or the medical industry build your gas gauge and pay thousands of dollars for it.

Use the reserve or blinking light as an indicator and be consistent with how you add gas and manually calculate MPG. Note any patterns or changes in case there are big unexpected changes.

At first I was annoyed the reserve appears to come up early but in reality it’s the safest thing to do. Imagine the Ch!t show here if folks got stuck in the side of the raid because they thought they had more gas than what was really there. That’s something to complain about.

Do you bitch if you find a $20 bill in your pants or are you grateful? Do the same thing with your gas. Just figure out your average fuel economy and ride. Enjoy life and stop sweating over the stupid little things. You can always go old school put a manual petcock and carburetors on your bike that way you’ll be consistent if it’s that big of a deal.

Morning grump out time for coffee!

 

[infrared]

The OP wanted to know his true gas mileage. Forget the bar gauge. I have a 2008. Does this approach (from an earlier post) not work, on a 2006? Here is a direct, real-time gas mileage readout:

That top bar on the gas gauge is not equal to the bar spacing you get from the lower bars, because the top of the tank is domed a bit. I believe you can choose to see the digital display showing your present gas mileage constantly in real time, on one line of the digital display. On my FJR, that information will displace some other (useless) info, I think Outside Air Temperature, but small loss, there. Your Owners' Manual should tell you how to set that up. If you do not have an Owners' Manual, somebody here will prolly have the link for a free download from Yamaha.

 

[RossKean]

The OP wanted to know his true gas mileage. Forget the bar gauge. I have a 2008. Does this approach (from an earlier post) not work, on a 2006? Here is a direct, real-time gas mileage readout:

Same on all Gen II. There is an "instantaneous" MPG readout that is almost useless except to show you how bad fuel consumption is under heavy acceleration or going uphill (updates every few seconds). The average MPG (since last reset) is more useful for sure. As I mentioned before, after a certain point, the readout is more of a running average for the last 300 miles or so, not since it was reset. (Older data gets dropped out.) I make a point of resetting one of my trip odometers and the average MPG every time I refill the tank.

Oh, if there was ever any question if the bike is truly metric... The average fuel consumption readout updates every kilometer on bikes destined for markets other than the US. The readout on a US bike is updated every 0.621... miles - exactly one kilometer.

 

[Ignacio]

I will have to try an keep an eye on my mileage. Thank you for your reply. Makes me feel a little better. Im gonna keep watching it.

So it's almost been a weeek. Have you fueled it up again and kept track of miles and gallons used from the pump? What was the actual MPG?

 

[Whooshka]

Until the OP does the math and gives us numbers we can't give him an idea of where to start looking. Forget the guages.

 

[torch]

Same on all Gen II. There is an "instantaneous" MPG readout that is almost useless except to show you how bad fuel consumption is under heavy acceleration or going uphill (updates every few seconds).

I did some playing with the instant MPG readout and I see the value as lying in the inverse -- a guide to throttle use to limit consumption while maintaining the best possible speed within that limit. EG on a long ride with planned fuel stops such as an IBR. So if I'm staring at a sign that says "Last Gas for 450kms" I know I have to keep my average consumption below 5.5 L/100Kms to make it.

As an experiment, I topped off the tank to exactly flush with the insert with the bike level and reset the trip meter. Then I headed out on the highway trying to maintain 5.0 +/- 0.1 L/100Kms rather than trying to maintain a constant speed. In truth, I did have outliers from 4.7 to 5.3 due to the lag when approaching or cresting hills, but generally I managed to maintain my target envelope.

Speed (by GPS, not that lying speedo on the dash) varied from 107Kph uphill to 124Kph downhill, which I think is a pretty respectable pace considering the posted limit is 100Kph. Not fast enough to attract undue attention, but not wasting much time, either. I usually roll along that stretch at about 110 to 115.

Next fuel stop was just under 190Km away. I topped off to exactly the same height with the bike level and did the math: Actual average was surprisingly close to the target, at 5.1L/100Kms.

As an aside, the average value display was 5.4L/100Kms at the start of the journey and dropped to 5.2 by the end.

So I wouldn't call it useless -- just not applicable to the way most of us ride.

 

[RossKean]

I did some playing with the instant MPG readout and I see the value as lying in the inverse -

I found the "instantaneous" (update every few seconds) only useful to see what riding habits (and conditions) are hardest on fuel. Not a surprise, but heavy acceleration, hill climbing, excess speed and headwinds make a big difference. Instructional rather than practical.

I usually reset the "average consumption gauge" when I fill to help estimate (along with trip odometer) how long I might expect to go before I need to fill again. It can be set in km/L which I find more intuitive for computations on the fly as compared with the L/100 km. The "average consumption" varies a lot after it is first reset (updating every kilometer) but steadies down after a time. Average since last reset, but only to a point - oldest data is removed from the computation after a time, but includes at least the last several hundred kilometers. I have found that the computed average km/L gauge to be in very good agreement with the actual calculated when I refill.

Note: US bikes have instantaneous and average mpg but no mode equivalent to L/100 km

 

[Old Guy]

The MPG on my '13 is actually pretty close over a long period of time -- at least it was the one time I checked it.
If I reset it and check it on one tank, it might be several tenths off. But on a trip some time back I decided to check it across several tanks, and it was within a couple of tenths of the my manual calculation. I haven't bothered doing it again, but it made sense to me that I may not fill precisely the same every time and checking it over several tanks sort of averages the differences.

That's my story, and I'm sticking to it.

 

[BigBlueF1]

So it's almost been a weeek. Have you fueled it up again and kept track of miles and gallons used from the pump? What was the actual MPG?

Hey! Funny thing, well, I havent had to fuel it up just yet. Im down to 2 bars now. Definitely got the most mileage on the 3rd, 4th and 5th bars. It says Im averaging 38.5 on my screen. I also checked my tires recently and my front was like 36 and the back was about 33. So i filled them up. I think that will make a big difference. I want to say from what Ive kept track of so far, not totally accurate but Ive gone about 120 miles on it and am down to the 2nd bar. So we'll see! Im going to fuel up soon and will know more and will keep more thorough count on it.

Sorry for the late response. I am very busy. I just read through 90% of the replies tonight and will read the rest tomorrow. Id like to take the power commander out honestly.

Thanks for the reply

 

[Ignacio]

t says Im averaging 38.5 on my screen.

That's not even close to "extremely low" as you suggested in your very first post with "Im only getting 8-10 miles per gallon?" Seems in the range of normal actually.

Moving on....

 

[torch]

It can be set in km/L which I find more intuitive for computations on the fly as compared with the L/100 km.

I can't argue with that. I don't know why the metric standard was flipped from distance/volume to volume/distance, but there it is. The FJR is one of the few vehicles that offers the option of Km/L but I left it the other way because all my other vehicles are that way so I learned to wrap my head around it.

From a technical point of view, I'm amazed these things are anywhere close to accurate. The ECU can't directly measure the volume of fuel used. The FJR doesn't even have a MAF. The fuel consumption must be based on totaling the injector pulse width over time* and is subject to manufacturing tolerances, variations between injectors and the fuel pressure applied to the injectors. With 4 injectors at 4,000rpm over, say, 3 hours that's 2,880,000 pulses! A lot of room for error.

*I doubt the ECU actually counts individual pulses. Probably uses an average pulse width. But each individual pulse would contribute to any error

 

[RossKean]

From a technical point of view, I'm amazed these things are anywhere close to accurate.

I don't know the computation algorithm used but I agree that it is astonishingly accurate - as good as refill-and-calculate (at least on my bike) given that you can be off ± a few hundred millilitres to "full", even if you are careful. I would have expected that variability between fuel injectors, among other factors, would be enough to bias the result. We know that the calculation is based upon what the ECU has told the injectors to do because when a Power Commander is placed in-line, the fuel consumption accuracy is way off (PC is usually used to add extra fuel in certain ranges but the ECU doesn't know that).

With 4 injectors at 4,000rpm over, say, 3 hours that's 2,880,000 pulses! A lot of room for error.

Four stroke engine so only one injection per cylinder for two revolutions but I get the point. I have no idea how it uses the pulse width/frequency data, or perhaps it just accumulates total open duration...?

I am certain that it is some sort of "running average" rather than "since last reset" - otherwise the value would never change once you had a dozen tanks through it. As far as I can recall, I haven't seen documentation on that.

 

[torch]

Four stroke engine so only one injection per cylinder for two revolutions but I get the point.

Ooops! Absolutely correct. It should read 1,440,000 pulses. My bad. Still a lot of room for error though.

I think the assumption of some sort of running average is supported by the results of my little experiment (average dropped from 5.4 to 5.2 L/100Kms in less than 200Km. Av was manually reset about 4,000Kms prior). The average could be time or distance, but given your observation that the instantaneous update rate is exactly 1Km even when displaying mpg, I suspect it is also based on the metric distance, likely somewhere between 300 and 500 kms.

A lot of computing power is being expended on that little display. Both in the initial creation and in the following discussion! <lol>. It brings to mind Douglas Adams' view of digital watches.

 

[Whooshka]

Hey! Funny thing, well, I havent had to fuel it up just yet. Im down to 2 bars now. Definitely got the most mileage on the 3rd, 4th and 5th bars. It says Im averaging 38.5 on my screen. I also checked my tires recently and my front was like 36 and the back was about 33. So i filled them up. I think that will make a big difference. I want to say from what Ive kept track of so far, not totally accurate but Ive gone about 120 miles on it and am down to the 2nd bar. So we'll see! Im going to fuel up soon and will know more and will keep more thorough count on it.

Sorry for the late response. I am very busy. I just read through 90% of the replies tonight and will read the rest tomorrow. Id like to take the power commander out honestly.

Thanks for the reply

Dude! Forget the gauges! Do the math. Fill up, ride and count the miles. Then fill up and divide those miles by the number of gallons you took in. That is your TRUE MPG.

 

[sullivan]

Hey! Funny thing, well, I havent had to fuel it up just yet. Im down to 2 bars now. Definitely got the most mileage on the 3rd, 4th and 5th bars. It says Im averaging 38.5 on my screen. I also checked my tires recently and my front was like 36 and the back was about 33. So i filled them up. I think that will make a big difference. I want to say from what Ive kept track of so far, not totally accurate but Ive gone about 120 miles on it and am down to the 2nd bar. So we'll see! Im going to fuel up soon and will know more and will keep more thorough count on it.

Sorry for the late response. I am very busy. I just read through 90% of the replies tonight and will read the rest tomorrow. Id like to take the power commander out honestly.

Thanks for the reply

Forget the bars as it's only a rough guide. Miles ÷ gallons at fill-up. 200+ before I casually think of a gas station. Easy.

 

[RiderJoe]

Like I said, the fuel gauge is just a "guesstimator". Or, a wet thumb in the air to judge where the wind comes from, etc. It gives you an approximate idea about how much fuel left in your tank (all bars indicate fuel up to the top, and the last flashing bar means that the pool is on its way to dry out), that's about how I look at it. MPG should not be judged by the fuel gauge. Use more precise instruments like your odometer or GPS, and the gallons readout on the fuel pump at full fill up to calculate that value.

 

[mcycleboy]

I had a serious look at doing something useful electronically to improve the gauge particularly at low levels, I gave up because the sender bottoms out with quite a lot of fuel left. I doubt bending the float wire would help much, the variable resistor was not at its limit when the float stopped moving.

Wrote it up here. The work was done on my 2010, it would read across certainly to any FJR 2006 or later, don't know about earlier

I appreciate mcatrophy sharing your considerable amount research with us. Lots of pictures and graphs to show exactly what you did. I can see after looking at your work why one cannot "adjust" the sending unit to get a wider range of readings. thanks much.

 

[mcycleboy]

Like I said, the fuel gauge is just a "guesstimator"

In the short time I have had my Gen 4 I have found out what you guys already know. RiderJoe is right - the fuel guage is just a guesstimator. Also the Range counter is of little value. On my bike after a fill up the range counter starts off at over 300 miles and stays over 300 miles for quite awhile!! I can't understand why Yamaha would even allow their software to put out a number that NO ONE can come close to getting range-wise. I am going to take the Range counter off the programable display as it just confuses me. Has anyone found any value to the Range counter? Also - my display of miles per gallon is ALWAYS optimistic. When I manually calculate the actual after filling up to the same exact level each time, it is about 3-4 mpg lower than what the bike's computer thinks. What good is it to have this information that is wrong always ?? Is this common with all FJR models around the world ?

Forgive me if I have missed this bit of information: What is actual run-out gallons/liters ?

Does anyone know what the actual runout gallons/liters is ? How far can one go before running out of gas and at that time how many gallons/liters does it take to fill it to the bottom of the tank fill "cup". Another way of posing the question is, after you go on reserve (trip-f) and start the count-up of numbers...how many miles or km will the bike travel before it totally runs out of fuel? I have never run it dry but I would like to know about what I can expect for miles/km after the last bar starts flashing. Thanks

 

[raesewell]

When I first get any bike a always perform a range test. Fill the tank put a gallon of fuel in the top box and run it for a day or two until it runs out. My figures were as follows 271.8 miles to empty with the reserve being 53.1 miles of that figure. The fuel icon starts flashing at around 220 miles

 

[RossKean]

Does anyone know what the actual runout gallons/liters is ?

I have put over 24.7 litres in my 25 litre tank so the pump manages to get pretty darn near all of it.

On my Gen II, the gauge does not have a "remaining range" function. It does go into a "count up" mode when there is very close to 6 litres remaining (1.6 USG). The gauge is rather non-linear - first and last quarter tanks are smaller than the middle two quarters. The "full to empty" of the regular (not reserve) portion of the tank represents three quarters of the total volume with the last quarter being the "reserve". Note: I believe that the Gen II and Gen III/IV sending units are very similar, if not identical.

I have always been highly impressed with the reproducibility of the fuel gauge, if not the absolute accuracy. Same with the average MPG meter if reset at the time of filling the tank - agrees with the amount to refill within five percent.

The gauge does not display accurately if the bike is parked on the sidestand! It will read significantly lower than when upright and moving - takes a couple of minutes to read right, especially when level is low. The gauge mechanism (and fuel pump) are on the right hand side. I have had the gauge go into low fuel "count up" mode on the side stand and then it decides, after a few minutes of riding, that there are still a couple of "bars" of fuel remaining and the count up trip odometer goes away until fuel is truly low.

If you want a near-useless fuel gauge, you should try the one on my 2017 BMW F700GS. It shows "Greater than half full" up until the point where there is actually less than a half tank. There is then a bar stack that drops in very rough proportion to fuel usage and a light that comes on with somewhere in the general vicinity of three to four litres left. Thankfully, the trip meter works and the average MPG function is fairly reproduceable, if not accurate. (It is not a malfunction, "They all do that" is the answer you get.) Mostly due to an irregularly shaped fuel tank that resides below the seat. (Click on image, below, for full size)


Quite honestly, the fuel gauge on the FJR is at least as good as I have seen on any other motorcycle once you understand its idiosyncrasies. I have NEVER been surprised in nearly 450,000 kilometers on the two Gen II's I have had. (My '07 and '11 behaved similarly although the first quarter tank on the '11 is closer than on the '07 - but still pessimistic.) As mentioned, I doubt it is worth trying to make it more accurate by bending the arm that connects to the float. Far more likely to mess it up further.