Mpg meter off by 4mpg - Page 6 - Yamaha FJR Forum : Yamaha FJR Owners Forums
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post #51 of 91 (permalink) Old 03-05-2019, 12:28 PM
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I think Mr. Ed has the right idea. Max torque is at 7000 rpm, max HP at 8000 rpm. Neither are going to provide ideal gas mileage, it's going to take more fuel to get that. Mass and wind resistance come into play and the load (gear you're in) at certain rpm is going to require a certain amount of fuel to maintain whatever speed. High load at lower rpm (e.g., randomly say 5th @ 3000 rpm) will require more fuel per injector pulse (longer duration pulse determined by ECU), than if you dropped down to 4th and increased rpm, less load, shorter duration injector pulses. Somewhere in there is ideal fuel efficiency for the speed travelled/wind resistance, and the lines will cross over, meaning go faster and upshift.... we don't know where all those lines are, but can intuitively learn when it's time to shift. Your fuel mileage is mostly determined by your riding habits, put 5 FJR's in a group on the same ride and you're roughly putting in the same amount of fuel at the next gas stop. My experiences from being accidentally in a lower gear, higher rpm, many times have shown better fuel efficiency from not having the engine under as much load.
Do I care that much? I'm not concerned about a few dollars of fuel on a long trip, it all averages out in the end. I don't slab much, I don't commute. I know roughly I get 40 km for every fuel bar that ticks off, always display my trip odometer because I know my usual range, I know when the last bar starts flashing I have 5 litres left to get me MAX 100 km, thus better find a gas station in the near future. I let the avg. fuel calculation ride most of the time and don't care if it changes a bit, and I stopped writing down fuel mileage a few years ago. The FJR is efficient enough even at its worst, so I'd rather think about my riding instead of fuel.

Ray
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post #52 of 91 (permalink) Old 03-05-2019, 03:23 PM
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Let me say a couple more things on this then i’ll shut up. Ever wonder what the advantage is of a CVT transmission is ? Well it’s because it puts the engine on it’s peak torque or the peak efficiency that is determined by the manufacturer from lots of testing but usually around the peak torque depending on what the “loud” pedal is asking for.

Torque vs horsepower vs rpm. Torque is a unit of work required to move a given load and is what really is the big thing here, it’s what an engine actually makes....(think of the lever on a torque wrench, when you pull on it that’s torque) so why isn’t a high torque Harley or Indian faster than an fjr? Well that’s where horsepower comes into it. Horsepower is only a mathematical calculation that shows an engines ability to rev (torque x rpm’s /5252 = horsepower) , the big twins may make more torque but they are sluggish to rev, no horsepower..... then you have to figure in engine and drive;one frictional loss’s. A good example is a blower motor, a blower motor will make way more power down low but the power required to spin a typical roots type blower starts to become more than gained with the boost, then add in the heat generated by compressing the air. Looking at all this, the fjr is a pretty good balance of torque and horsepower.

It’s all a compromise

Steve P
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post #53 of 91 (permalink) Old 03-07-2019, 08:04 PM
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I’ve put >6,000 miles on my 2018, use Roadtrip app on phone to calculate mileage at every fill up, and can agree that the bike over-reports average mileage by ~10%. It usually tells me my average is ~44 but in reality it’s ~40.
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post #54 of 91 (permalink) Old 03-08-2019, 11:28 AM
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The Maths is good
use The Maths

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post #55 of 91 (permalink) Old 03-08-2019, 06:31 PM
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Reset my ave fuel consumption, reset my Trip 2, filled up and took off. After 198.7 miles gauge said I average 48, math said I averaged 45. So off by 3 mpg on this tank.

2018 Yamaha FJR 1300A
2014 Honda CB1100 DLX

It doesn't matter what I ride, where I ride, or how far I ride... it only matters THAT I ride...every day. "Ferret"
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post #56 of 91 (permalink) Old 03-08-2019, 08:06 PM
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Must be winter 6 pages about the fuel gauge
bounce, slowdave and rubiete like this.

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post #57 of 91 (permalink) Old 03-08-2019, 10:30 PM
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Who remembers when the factory installed vacuum gauges on cars to help you get better MPG?
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post #58 of 91 (permalink) Old 03-09-2019, 08:50 AM
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Quote:
Originally Posted by 2014oldred View Post
Who remembers when the factory installed vacuum gauges on cars to help you get better MPG?

Vacuum or not, our 2013 Subbie has an "analog" gauge that acts just like that.

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post #59 of 91 (permalink) Old 03-09-2019, 09:36 AM
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Originally Posted by MrZappo View Post
Well, good luck with that. It's an estimate and it is (like cars) based on a best guess at the time. Without actual fuel flow data.

The only way to be accurate would be to have an actual fuel flow meter. Which no manufacturer would pay for.

So the only choice would be to reprogram the computer logic and adjust whatever algorithm is used to "estimate" what your mileage is to account for how you ride in relation to whatever they considered a "normal" rider at the time.

And considering that they have to play games with the government regarding co2 per "whatever" per mile etc etc etc, it is a losing battle.

So, I applaud your tenacity.
Actually, it's a pretty tight estimate, if the mfg'er isn't swayed by marketing.

The injectors are mapped for their delivery vs. "on-time". In other words, they know that if the injector is on for 1 ms, it delivers x mg of fuel. Multiply by shots/second (function of engine speed) and number of injectors, and you have the fuel flow. Typically, this value should be pretty easily within 2-3%, maybe as poor as 5% at very low flowrates like low idle. Many manufacturers lean the table a little though. In my experience, these trip computers are almost never low on their mpg estimates. I'm a data nerd and have a lot of data on all my vehicles. Some run a consistent 4% high and others run very close to right on the number. My 2008 FJR is one of the better ones, averaging 0.6% high (meter vs. actual fill-up calculated mpg), with a standard deviation of 3% though. So, basically, it's running almost straight on the number on average, with most tanks coming in within +/- 3%. So my trip computer is normally within +/- 1.5 mpg and scattered pretty evenly high and low so the average is within 0.3 mpg (probably as good as my precision on a refill).

As far as I know, there are no CO2 nor CAFE (fuel economy) regs on motorcycles at this moment. And even if there are/were, those regs in no way involve the fuel mileage calculators on cars. The EPA is not going to take the fuel mileage meter as gospel, that is for sure! So, the mfg'er can do whatever they want on the mpg meter--the EPA could care less.
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post #60 of 91 (permalink) Old 03-09-2019, 09:46 AM
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Originally Posted by JohnC View Post
Ride more. Obsess less. Pay attention to the fuel gauge.
What if I enjoy obsessing? Don't tell me how to live my life! Lol.

We can't ride 24x7. We all have some strange interests. Some of us are interested in fuel consumption data. To each his own, imho.
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