06-A Avg. MPG incorrect?

[DrBunsen]

On page 3-6 of the manual for the '06 A model, under "Average fuel consumption mode" it says:

This display shows the average fuel consumption since it was last reset." It also tells you how to reset it.

Well... I've never reset mine. I've got hundreds of miles on my FJR, and as the miles rack up it should be more and more difficult to affect the average.

But take yesterday for instance. In the parking garage when I started it up, it showed 45.3 MPG as the average. I let it idle for a couple of minutes while I put on my gear. I rode it at slow speeds down the 10 levels of the garage. By the bottom the AV MPG was at 44.7.

There's no way that 4 or 5 minutes that the engine was running could have influenced the many hours of other travel so much. So, one of three things is up:

1) There's something wrong with my particular bike.

2) It's a flaw on everyone's bike, like the 17 MPG instant reading.

3) It doesn't really keep all the data since the last reset, but instead it remembers the last X number of miles of data (because it obviously doesn't have limitless storage to remember data points). Or maybe when it's turned off it stores the current value as a data point with a large influential value, but not one that's indicative of the actual amount of miles traveled.

Or it may be that it's a combination of #1 and #3, or #2 and #3.

Have any of you guys noticed this?

 

[slapnpop]

I remember reading somewhere about it only being the average for the last X miles, or since reset.

I vote #3

 

[Woodstock]

On page 3-6 of the manual for the '06 A model, under "Average fuel consumption mode" it says:
This display shows the average fuel consumption since it was last reset." It also tells you how to reset it.

Well... I've never reset mine. I've got hundreds of miles on my FJR, and as the miles rack up it should be more and more difficult to affect the average.

But take yesterday for instance. In the parking garage when I started it up, it showed 45.3 MPG as the average. I let it idle for a couple of minutes while I put on my gear. I rode it at slow speeds down the 10 levels of the garage. By the bottom the AV MPG was at 44.7.

There's no way that 4 or 5 minutes that the engine was running could have influenced the many hours of other travel so much. So, one of three things is up:

1) There's something wrong with my particular bike.

2) It's a flaw on everyone's bike, like the 17 MPG instant reading.

3) It doesn't really keep all the data since the last reset, but instead it remembers the last X number of miles of data (because it obviously doesn't have limitless storage to remember data points). Or maybe when it's turned off it stores the current value as a data point with a large influential value, but not one that's indicative of the actual amount of miles traveled.

Or it may be that it's a combination of #1 and #3, or #2 and #3.

Have any of you guys noticed this?

I have no idea, really, but I would point out you don't need "limitless" or even all that much storage to compute a true running average since reset.

 

[DrBunsen]

I have no idea, really, but I would point out you don't need "limitless" or even all that much storage to compute a true running average since reset.

Doh! Yep, I knew better than that. One of the programs I use to monitor routers (MRTG) very efficiently stores lots of data.

 

[Ari Rankum]

I have no idea, really, but I would point out you don't need "limitless" or even all that much storage to compute a true running average since reset.

Doh! Yep, I knew better than that. One of the programs I use to monitor routers (MRTG) very efficiently stores lots of data.

I think what Woodstock is getting at is that you could do the math with only two storage locations and one sensor input/temporary variable for the current reading.

avg_mpg = ((avg_mpg * total_num_samples) + current_mpg) / (++total_num_samples)

As long as the memory locations you choose to accomodate the avg_mpg and total_num_samples do not overflow during the lifetime of the bike, the amount of storage required never increases over the two or three (depending on whether current_mpg is an input from a sensor) used above. The only variable that would ever overflow would be total_num_samples. If you used a 32-bit storage location and sampled mileage once a second, you could run your bike 7x24 for 136 years without an issue.

 

[odot]

Ow, my head....I knew it was the wrong time to stop sniffing glue.

 

[fjrtx]

Got my 06 from D&H last week and was surprised that my instant mileage was working perfect. Rode out with another FJR rider from Texas and his worked also. Yamaha fixed this problem very quick. Thanks Yamaha. Love the bike.

 

[bmwhd]

Got my 06 from D&H last week and was surprised that my instant mileage was working perfect. Rode out with another FJR rider from Texas and his worked also. Yamaha fixed this problem very quick. Thanks Yamaha. Love the bike.

Sure would be nice if they would share with the rest of us '06 owners :angry2:

 

[Diesel]

On page 3-6 of the manual for the '06 A model, under "Average fuel consumption mode" it says:
This display shows the average fuel consumption since it was last reset." It also tells you how to reset it.

Well... I've never reset mine. I've got hundreds of miles on my FJR, and as the miles rack up it should be more and more difficult to affect the average.

But take yesterday for instance. In the parking garage when I started it up, it showed 45.3 MPG as the average. I let it idle for a couple of minutes while I put on my gear. I rode it at slow speeds down the 10 levels of the garage. By the bottom the AV MPG was at 44.7.

There's no way that 4 or 5 minutes that the engine was running could have influenced the many hours of other travel so much. So, one of three things is up:

1) There's something wrong with my particular bike.

2) It's a flaw on everyone's bike, like the 17 MPG instant reading.

3) It doesn't really keep all the data since the last reset, but instead it remembers the last X number of miles of data (because it obviously doesn't have limitless storage to remember data points). Or maybe when it's turned off it stores the current value as a data point with a large influential value, but not one that's indicative of the actual amount of miles traveled.

Or it may be that it's a combination of #1 and #3, or #2 and #3.

Have any of you guys noticed this?

My 06 is the same way.....a cold engine realy kills the MPG.

Before I can get out of my neighborhood the average MPG takes a hit.

I've been obsessing about it for a week now :crazy: ........So I've just turned it off and view the air temp instead. Instantaniuos MPG doesn't work......don't really care.....it would be just another distraction for me that I don't need while I'm on the bike.

 

[ShinyPartsUp]

I've noticed my avg mpg does fluctuate more than I'd expect, but after two tanks checking it the old fashioned way (miles/gallons of fuel consumed) it is accurate within a tenth or two. Sorry if the glue sniffers have trouble with that

As for the instant MPG, my mechanic looked everywhere and there are no Yamaha bulletins about it. Mine doesn't work, but if they have to dismantle the whole dash to fix it, I think the risk of gremlins happening due to the fix outweigh the usefulness of the instant MPG function, IMHO.

 

[jimbemotumbo]

Hundreds of miles is not enough to limit the changes you see (and they are so very slight too). What you are describing is perfectly normal behavior. You'll likely need several thousand miles for the avg mpg to settle down. Although I have the instant mpg bug, my average is spot on and suspect all bikes are (since they use the same algorithm).

 

[DrBunsen]

Hundreds of miles is not enough to limit the changes you see (and they are so very slight too). What you are describing is perfectly normal behavior. You'll likely need several thousand miles for the avg mpg to settle down. Although I have the instant mpg bug, my average is spot on and suspect all bikes are (since they use the same algorithm).

I don't agree. Let's do the math....

Here's an estimate of what happened:

Let's say I started off with 800 miles at 45.3 MPG. That means that I burned through 800/45.3 gallons of gas to get to that point, or 17.66 gallons.

1 mile later I would've been at 801 miles at 44.7 MPG. 801/44.7 is 17.92 gallons. The difference between them is more than a quart of gas.

I'd be very very surprised if I burned through a quart of gas in that 1 mile. Be aware that most of the mile was with the engine idling since I was going downhill in the parking garage, mostly with the clutch engaged.

 

[jimbemotumbo]

too many variables. makes my head hurt. i like my variables thus far ... no less than 48 mpg on the last 5 tanks ... commuting miles too.

 

[Woodstock]

I have no idea, really, but I would point out you don't need "limitless" or even all that much storage to compute a true running average since reset.

Doh! Yep, I knew better than that. One of the programs I use to monitor routers (MRTG) very efficiently stores lots of data.

I think what Woodstock is getting at is that you could do the math with only two storage locations and one sensor input/temporary variable for the current reading.

avg_mpg = ((avg_mpg * total_num_samples) + current_mpg) / (++total_num_samples)

As long as the memory locations you choose to accomodate the avg_mpg and total_num_samples do not overflow during the lifetime of the bike, the amount of storage required never increases over the two or three (depending on whether current_mpg is an input from a sensor) used above. The only variable that would ever overflow would be total_num_samples. If you used a 32-bit storage location and sampled mileage once a second, you could run your bike 7x24 for 136 years without an issue.

Exactly. :thumbsup:

 

[DrBunsen]

too many variables. makes my head hurt. i like my variables thus far ... no less than 48 mpg on the last 5 tanks ... commuting miles too.

Well... Count me as being *jealous*!

My milage has been getting better and better as it breaks in. I certainly wouldn't mind it ending up being in the 48MPG range.

 

[painman]

I'm with you doc, but you got to stop doing those burnouts in the parking garage. Your scaring the clients. I do agree though, my milage should be better but as the miles mount up, it seems to be slowly improving. PM. <><

 

[DrBunsen]

I remember reading somewhere about it only being the average for the last X miles, or since reset.

Yep, I'm convinced that that's the case, and so the documentation is inaccurate. Here's how I tested:

I filled up while on center-stand (to insure a fairly consistant tank fillup) and reset my Avg MPG. Next 2 fillups were also on center-stand and I haven't reset the Avg. MPG since the one time 2 tanks ago. I did one tank with semi-non-conservative riding (well, for ME it was fairly non-conservative - most of you guys would still think I was dawdling like a grandmother), higher speeds, greater accelleration, etc. The next tank I was somewhat more conservative. At the end of the 2 tanks of gas here were the stats:

Tank 1:

Miles: 193.6

Gallons: 4.485

True MPG: 43.16

Indicated Avg MPG: 43.1

Tank2:

Miles: 217.4

Gallons: 4.778

True MPG: 45.50

Indicated Avg MPG: 45.4

Combined 2 tanks:

Miles: 411.0

Gallons: 9.263

True MPG for both tanks: 44.37

Indicated Avg MPG: 45.4 <=according to manual that should be for both tanks

So, it looks like the Avg. MPG indicator really is only for a recent amount of miles, and appears to be fairly accurate for the most recent tank of gas. It definitely doesn't keep track of stats since the last reset.

I'm OK with that, and in fact I kinda like it better this way. It ends up being a pretty good indicator of what I'm doing with that tank of gas. I just wanted to pass along that it doesn't work as described in the owner's manual. Hopefully when I get the 17MPG thing fixed they don't also "fix" this issue.