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All 650Rs Fuel consumption inaccuracy

hotrob

2019
CB650R ABS
Mar 12, 2019
Has anyone else noticed that the CB650R's average fuel consumption readout is inaccurate? I've coveraged about 800 miles on my CB650R and these are the fuel consumption figures from the trip computer readout and my manual calculations after each refilling of the petrol tank:

Dash display: 64.0 61.6 60.7 61.8 58.4 60.7 mpg - average so far 61.2mpg
Calculated: 63.2 67.4 68.4 64.7 65.0 68.5 mpg - average so far 66.2mpg

The average difference so far is that I'm actually getting about 10% more mpg than the trip computer is telling me. The last few bikes that I've owned have had quite accurate trip computer readouts, but it seems that this Honda is not as accurate.
 

Psnake

2019
CBR650R ABS
Apr 2, 2019
Has anyone else noticed that the CB650R's average fuel consumption readout is inaccurate? I've coveraged about 800 miles on my CB650R and these are the fuel consumption figures from the trip computer readout and my manual calculations after each refilling of the petrol tank:

Dash display: 64.0 61.6 60.7 61.8 58.4 60.7 mpg - average so far 61.2mpg
Calculated: 63.2 67.4 68.4 64.7 65.0 68.5 mpg - average so far 66.2mpg

The average difference so far is that I'm actually getting about 10% more mpg than the trip computer is telling me. The last few bikes that I've owned have had quite accurate trip computer readouts, but it seems that this Honda is not as accurate.
Well it's better than worse lol
Anyway I assume your mileage is from the odometer? I think the bike reads higher than actual speed by like 10%, would this causing a higher mileage reading by 10% as well? If this is true then 66.2 x 10/11 = 60.2 mpg actual.
 

hotrob

2019
CB650R ABS
Mar 12, 2019
I assume your mileage is from the odometer? I think the bike reads higher than actual speed by like 10%, would this causing a higher mileage reading by 10% as well?

My manual calculations were using trip meter A. However, I would expect that trip A, trip B, the odometer and the speedometer would all use the same distance travelled data, possibly from a sensor on the output shaft from the gearbox. I would also expect that the trip computer would use the same data for its calculation of mpg, so if it is under-reading distance by 10% then my calculations should also under-read mpg by 10%. So my guess would be that its measurement of fuel used is over-reading by about 10%. I don't know if it's just my bike or whether they are all equally inaccurate.

But maybe you're right. Perhaps Honda know that they deliberately over-read distance by 10% so that the speedo over-reads, but they allowed for that in their calculations of mpg. Without knowing the exact distance that I travel it's dificult to know for sure. But with my previous bikes (and cars) my calculated mpg and the trip computer mpg figures have been more in agreement than it is with this Honda.
 

guille.g.l

2019
CBR650R ABS
Jul 31, 2019
Spain
I have detected the same inaccuracy on my bike but I think it is related with fuel consumption sensor and not with odometer. The other day I arrived to the gas station after riding 40km with fuel reserve. Dashboard indicated that I had consumed more than 16 litres (impossible beacuse tank is 15,4L), however I filled up only 14 litres until the maximum was reached. Be noted that I always reset trip A, fuel consumption, etc. after refuel.
 

Darwade

2018
CBR650F ABS
Feb 1, 2019
I think it's about the sensor reading time. If you track the average consumption it only shows arround each 2 seconds. So your manual calculations will be better...
 

Danny Linguini

2020
CB650R
Apr 26, 2020
Riding Since
1974
Pardon the necro-post, but I had a few ents to throw in.

First off, the OP’s noted displayed and actual mileage in the 60’s? Wow. I just filled up today after my first full tank and didn’t pay attention to the calculated average MPG, only the indicated MPG while riding, which usually seems to be around 45 whenever I look while riding on relatively flat, level roads. I’ve seen it go as low as 35-ish when starting off or going up hills, and as high as 55-ish going down hills. But it’s usually hovering in the 40’s, which kind of surprised me for a 650. Anyway, calculated mileage on the first full tank was over 55 - 171 miles on 3.1 gallons, which is much closer to what I expected. Needless to say I was quite pleased with that.

Anyway, just wondering what everybody else’s indicated real-time mileage is vs. actual calculated.

Edit: Just remembered I could check tripmeter B, which says average is 47.5 MPG, and total which says average is 48 MPG, both in the range I observed real-time, and both significantly lower than what I calculated.
 
Last edited:

Danny Linguini

2020
CB650R
Apr 26, 2020
Riding Since
1974
Don't forget that I'm in the UK, so we use imperial gallons which are about 20% more than US gallons. So 55 mpg US is 66 mpg UK.
Ah - that explains that. :) I thought you guys were all metric over there, so I was confussed.
 

Rafe

2019
CBR650R ABS
Oct 1, 2019
United Kingdom
Ah - that explains that. :) I thought you guys were all metric over there, so I was confused.

Don't get me started. We're a mixed bag of metric and imperial. I can't speak for everyone but in my experience, we measure in mm/cm, but your height measurement in feet and inches, weigh stuff in the kitchen in grams but our body weight in lb and ounces and we buy 2 pints of milk but buy a 500cl bottle of water?

Measuring something in inches gets me every time though. I watch a lot of woodworking videos and when they say "You need to shave off about 17/64's of an inch" I'm like what on earth is that?
 

xavi

2019
CBR650F ABS
Dec 6, 2019
My CBR650F does the same, and I know why they do it.
The sensor in the tank has a top max position, meaning the ecu reads it when you fill all the way up.
BUT if you fill the tank with the bike on upright position, you can put in an extra 1-1.5 liters of fuel.
If you fill up on the side stand, it will have less fuel going in, BUT the ecu reads it as a full tank too.
So if you fill it on the side stand the ecu will start counting the spent fuel with a diference that turns into that mpg difference on the next tank...
If you fill the tank on an upright position, the mpg will be accurate.
Do it and you can confirm. I have done it many times and it's always like that...
 

CrazyTugz

2019
CB650R ABS
Mar 23, 2020
Portugal
Riding Since
2019
My CBR650F does the same, and I know why they do it.
The sensor in the tank has a top max position, meaning the ecu reads it when you fill all the way up.
BUT if you fill the tank with the bike on upright position, you can put in an extra 1-1.5 liters of fuel.
If you fill up on the side stand, it will have less fuel going in, BUT the ecu reads it as a full tank too.
So if you fill it on the side stand the ecu will start counting the spent fuel with a diference that turns into that mpg difference on the next tank...
If you fill the tank on an upright position, the mpg will be accurate.
Do it and you can confirm. I have done it many times and it's always like that...
interesting, gotta test that out too
 

FogDucker

2018
CB650F ABS
Apr 3, 2019
Canada
U guys took it to the next level .I hold half a tank full when my fuel gauge starts flashing. When I reach 4.0 and flashing I still have 80 90 km to go. So I have given up on all the calculations this little trip computer provides.... :(
 

FogDucker

2018
CB650F ABS
Apr 3, 2019
Canada
My CBR650F does the same, and I know why they do it.
The sensor in the tank has a top max position, meaning the ecu reads it when you fill all the way up.
BUT if you fill the tank with the bike on upright position, you can put in an extra 1-1.5 liters of fuel.
If you fill up on the side stand, it will have less fuel going in, BUT the ecu reads it as a full tank too.
So if you fill it on the side stand the ecu will start counting the spent fuel with a diference that turns into that mpg difference on the next tank...
If you fill the tank on an upright position, the mpg will be accurate.
Do it and you can confirm. I have done it many times and it's always like that...
was always a question to me
 

CBJojo650RRR

2019
CBR650R ABS
Apr 26, 2020
Riding Since
2019
I’ve also noticed this today. Fill it up to the rim (every time) and calculated the fuel consumption to be 4.7L/100km. The trip meter reports 5.5L/100km.
 
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