Economy Accuracy

[cpettifer]

Anyone noticed that the economy computer isn't actually very accurate?

In 1,000 miles I've averaged 53.7mpg, according to the computer. The last tank being better than that as it improved the figure. However, I went 210 miles on 19 litres. This is only just over 50mpg. Can anyone explain why this should be so?

[mecki]

Well, I noticed that the tyre pressure has a huge effect; is the pressure of the front wheel a bit low the fuel economy seems to increase.
An other problem is filling the tank to exactly the same mark every time.
So I always take those numbers with a pinch of salt. ;D

[coastrider]

The front tyre will affect the accuracy as the speed/distance is taken from revolutions of the front wheel, so if the pressure drops it reduces the outside diameter of the tyre and the bike thinks its going faster.
You also have to bear in mind that speedo's are allowed to over-read by up to 10% but not under-read. This accounts for some variation as would changing the tyres to different makes from those used to callibrate the system.
As with fuel guages; I would only use it as a guide.

[routemaster]

Hi

The "average" mpg is just that an average of mpg since the last time the computer was reset. Over time the more data it collects the less the average will change - statistical curve, analysis and all that stuff.

Working out your average mpg from the amount of fuel you out into the tank against number of miles will always vary as it relies on filling the tank to  exactly the same level every time. I am not sure where the computer gets the info about the amount of fuel consumed, if it is from the fuel management/injection system then it would be very accurate, if it is from the fuel gauge then perhaps not as accurate but it does give a good "guide"

Kind regards

Steven

[pembsgtr]

I just put the petrol in and ride the bike, if I was worried about fuel economy I would have bought a BMW  ;D 

[Lonewolf]

I suppose the MPG is a general guide and indicator as to how the bike is running but it aint no scientific application. If I suddenly started getting 40 mpg instead of the 50+ I currently get then that would set the alarm bells ringing.

[Rusty]

Nice one Pembsgtr .... I just fill it up till it sloshes to the top .....  ;D BUT, my mpg seems to be getting better, despite giving the bike serious wellington in France and more now that everything is run in I am now showing 49.3 ( I think ) ... TP's show 42 each end. Strange but true !