Why 40mpg?

ironsheik

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Manchester.
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W204 C200CDI SPORT.
Just curious to know why when you reset the "From Start" on the dashboard, the mpg is 40?

Is there a specific reason for this?
 

cinek

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Herts
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MB W204 , BMW F10, GSXR LZ3
It isnt on my car.

When reset the mpg, I get three horizontal lines showing for about 20s, then come the numbers, which for initial 20min or so, are all over the place.
Unless I am currently on the motorway, cruising at low, steady speed.
 

whitenemesis

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Is it the same as the ave mpg from the last reset screen?
 
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ironsheik

ironsheik

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Location
Manchester.
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W204 C200CDI SPORT.
Is it the same as the ave mpg from the last reset screen?

No, its doesn't matter what the mpg is on the "Last Reset" screen, when the "From Start" screen is reset, the mpg always starts from 40mpg..:confused:..
 

Dryce

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..
When you reset the onboard computer is left with a problem. At what point does it start displaying a number - because you have to drive it a few miles before the number will become meaningful.

It has the same problem in calculating the range display.

The solutions are:


  • start with a display such as dashes and run like this until enough data is average to give a meaningful number and then start displaying it.
  • start by displaying numbers that are unrealistically all over the place - particularly if the driver is in urban stop/start or driving gently down some long hills.
  • start by displaying a middling seed value and seed the averaging system so that looks sensible and then let the number drift gradually as the averaging system gets filled with real numbers.

Basically when you're seeing 40mpg after reset the MB designers have gone with the third option and chosen to seed the setup at 40mpg.

This will also be tied in with the range calculation and makes the initial reset range look sensible.
 
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ironsheik

ironsheik

Active Member
Joined
Feb 13, 2011
Messages
195
Location
Manchester.
Car
W204 C200CDI SPORT.
When you reset the onboard computer is left with a problem. At what point does it start displaying a number - because you have to drive it a few miles before the number will become meaningful.

It has the same problem in calculating the range display.

The solutions are:


  • start with a display such as dashes and run like this until enough data is average to give a meaningful number and then start displaying it.
  • start by displaying numbers that are unrealistically all over the place - particularly if the driver is in urban stop/start or driving gently down some long hills.
  • start by displaying a middling seed value and seed the averaging system so that looks sensible and then let the number drift gradually as the averaging system gets filled with real numbers.

Basically when you're seeing 40mpg after reset the MB designers have gone with the third option and chosen to seed the setup at 40mpg.

This will also be tied in with the range calculation and makes the initial reset range look sensible.


Thanks for that, it makes sense..
 

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