avg. mpg stuck at 37

[smccormilla]

The trip computer on my 08 FJR (US import to the UK) shows the avg. fuel consumption as being 37 mpg (us gal) and appears to be stuck at this.

I noticed a while back the fuel gauge dropped to show reserve just as I started it, even though there was plenty of fuel left. Not unusual when first starting up in the morning, but rather than clicking back to a bar or two a few miles later it showed full then went completely blank. It did this once more and then appeared to work again, but was very optimistic, 24lts of fuel with fuel gauge still showing 2-3 bars. The next fill up and all the rest have been fine, but the av consumption has stayed at 37, which unfortunately is not the case. Is it just a coincidence that the fuel gauge and avg consumption went funny at about the same time?

Anyone else had a similar experience or know why, I see that there was a problem with 06 models showing 17mpg on the instant?

 

[UselessPickles]

Are you getting consistent average mileage based on how much fuel you are putting in? The average MPG display is probably optimistic, because the speedometer is optimistic. Speed and MPG are both calculated based on the same signal from the wheels that is processed into a higher-than-actual speed.

Try resetting the average MPG to be sure that it is actually being calculated rather than being truly "stuck" on 37.

 

[RadioHowie]

To the knowledgeable:

Could this symptom be a precursor of an imminent spider bite?

 

[smccormilla]

Uselesspickles, it's not a problem with how it's working out the consumption it's that the computer has stuck on 37mpg. The instant consumption is still working and if I thrash it on the commute the avg normally drops to around the 32mpg mark and if I'm careful I can get it up to 40mpg, but it's always changing on the display, use to anyway.

I thought at first about this spider thing, but seeing the thread on problems on early 06 bikes made me think it could be something else. I just hoped to have a bit more info before going back to the dealer.

 

[mvette]

The more miles you put on the average readout without ever reseting it the slower the change will be. Have you reset it latley?

 

[RadioHowie]

Now THAT'S a good point!

 

[zenwhipper]

The more miles you put on the average readout without ever reseting it the slower the change will be. Have you reset it latley?

+1 Yep.

 

[smccormilla]

Mine always seemed to reset with every tank. When I fill up I'm in the habit of reseting the trip, previous bikes never had fuel gauges. I always assumed this would reset the avg mpg, hence it always changing with every few miles. It's been stuck on 37 mpg for more than a 1500m now, that's not right.

 

[BkrK12]

I'm not seeing that you actually reset it. Why not give it a try and see what happens?

 

[dsmack]

I think "mvette" has hit the nail on the head! Well played, Sir!

On my recent 2300 mile trip south, I noticed that after about 4 or 5 tankfuls of gas, that the Average MPG readout was getting more and more sluggish, so I reset it on the 6th tank. For the next thirty or so miles after that, it acted almost like the usually quicker (nearly instantaneous...) readout of the other MPG readout.

I wonder how big the buffer is for the "Average MPG" function? It would help to flush it so it is working with a smaller data set. Then each change, such as temporary aggressive throttle use, would show a corresponding larger change in the calculated average because the Change input would be a larger percentage of the total data set.

Let us know what happens after you reset it???

 

[olsonm3915]

I think "mvette" has hit the nail on the head! Well played, Sir!
On my recent 2300 mile trip south, I noticed that after about 4 or 5 tankfuls of gas, that the Average MPG readout was getting more and more sluggish, so I reset it on the 6th tank. For the next thirty or so miles after that, it acted almost like the usually quicker (nearly instantaneous...) readout of the other MPG readout.

I wonder how big the buffer is for the "Average MPG" function? It would help to flush it so it is working with a smaller data set. Then each change, such as temporary aggressive throttle use, would show a corresponding larger change in the calculated average because the Change input would be a larger percentage of the total data set.

Let us know what happens after you reset it???

I'm somewhat boggled by the question. There is no "buffer" as such, other than perhaps a 32 or 64-bit number representing the counting increment of fuel used, and another register that tracks distance traveled since the AVG MPG display was last reset . The computer simply tracks how much fuel is being used by counting a tiny amount of fuel every time an injector sprays. It knows how long the injector is open (because it told it when to open and close) and it knows the approximate pressure differential across the injector, hence it can calculate how much fuel was sprayed out. If you know how much fuel was used since the last reset, and how many miles have been traveled, the average mpg will converge to a remarkably steady number- just like my average fuel number in my total mileage log (I admit OCD) hasn't budged by even a tenth of an mpg for quite a long time now, after 27k+ miles. No mystery at all.

I reset my AVG display every time I fill up, and compare it with the mileage figured by dividing what the gas pump tells me into the trip meter reading. They're usually not all that close but they average out to match up pretty well, due to variations in how full I fill the tank. I don't try to get it all the way to the top, I just stop fairly soon after the level reaches the bottom of the filler neck thingy.