Mileage computer max miles before dumping data?

[Rubber Ducky]

If not reset manually, at some point the onboard mileage computer dumps earliest data to replace it with current incoming data. Thus (if not reset) the average mileage shown is a rolling number over the last 'n' miles. Anyone know what 'n' is?

[SHADOW4]

Originally Posted by Rubber Ducky

If not reset manually, at some point the onboard mileage computer dumps earliest data to replace it with current incoming data. Thus (if not reset) the average mileage shown is a rolling number over the last 'n' miles. Anyone know what 'n' is?

x+y=n?

n= any number?

Don't know, i should have stayed in school..............

[Memphis1]

which mileage?? do you mean trip computer? or MPG?

trip computer just rolls back to zero, MPG continues getting an average.

[Rubber Ducky]

Originally Posted by memphis2012

which mileage?? do you mean trip computer? or MPG?

trip computer just rolls back to zero, MPG continues getting an average.

MPG. Yes, continues to get average, but at some point the miles register gets full and it dumps earlier data - recall this from earlier discussion some time back. Thus shows average over last - say - 5000 miles, even if last reset was farther back than that. Just curious for how many miles it keeps.

[teagueAMX]

Originally Posted by SHADOW4

x+y=n?

n= any number?

Don't know, i should have stayed in school..............

LOL - It's been almost 40 years and I'm a little vague on my algebra, but it seems you have to have at least one or two values before you can find n. Of course, then again, my kids might be able to do it and I just forgot how.

[Rubber Ducky]

Originally Posted by teagueAMX

LOL - It's been almost 40 years and I'm a little vague on my algebra, but it seems you have to have at least one or two values before you can find n. Of course, then again, my kids might be able to do it and I just forgot how.

Am not trying to solve for 'n.' Am trying to learn the max number of miles the computation holds before it dumps data. "N."

[teagueAMX]

Originally Posted by Rubber Ducky

Am not trying to solve for 'n.' Am trying to learn the max number of miles the computation holds before it dumps data. "N."

I know, Ducky - I was responding to SHADOW4 that I thought was funny.

Originally Posted by SHADOW4
x+y=n?

n= any number?

Don't know, i should have stayed in school..............

Pardon my off beat sense of humor.

[rmorin49]

No answer to Ducky's question?

[teagueAMX]

To answer that definitively, my guess is someone would have to have access to the various program variables within the ECU or iDrive.

It's a fairy simple question but getting there is a fairly technical answer. Maybe one of Dinan's programmers? Dealer? FWIW

[zEdP]

Let's assume that n=life time of the car in miles or km's.

So let’s be a little bit nerdy.I guess the software calculates the number of miles driven and the delta fuel consumed between the engine was started and stopped, so one trip. For every trip this data is added to the total fuel consumption and miles. The last new average is used when driving, a software calculated fuel flow is calculated and used to average the total consumed fuel and total miles driven. The fuel flow calculation is thrown away when you stop the engine to perform again the delta fuel consumption and miles driven of your last trip.

…….Just a wild guess…....

[SHADOW4]

Originally Posted by zEdP

Let's assume that n=life time of the car in miles or km's.

So let’s be a little bit nerdy.I guess the software calculates the number of miles driven and the delta fuel consumed between the engine was started and stopped, so one trip. For every trip this data is added to the total fuel consumption and miles. The last new average is used when driving, a software calculated fuel flow is calculated and used to average the total consumed fuel and total miles driven. The fuel flow calculation is thrown away when you stop the engine to perform again the delta fuel consumption and miles driven of your last trip.

?????

I should have stayed in school!

What?

[juhap]

Originally Posted by zEdP

…….Just a wild guess…....

Makes perfect sense to me.

[Rubber Ducky]

Originally Posted by zEdP

Let's assume that n=life time of the car in miles or km's.

So let’s be a little bit nerdy.I guess the software calculates the number of miles driven and the delta fuel consumed between the engine was started and stopped, so one trip. For every trip this data is added to the total fuel consumption and miles. The last new average is used when driving, a software calculated fuel flow is calculated and used to average the total consumed fuel and total miles driven. The fuel flow calculation is thrown away when you stop the engine to perform again the delta fuel consumption and miles driven of your last trip.

…….Just a wild guess…....

Maybe sounds good, but it does not dump the previous data ... until a much later time. I somehow seem to recall a number like 2,000 miles for a much earlier version in a BMWE but would expect memory size now big enough to retain many more miles of information.

Guess I'll just put this one in the too-hard pile.

[Memphis1]

the concept doesn't make sense, otherwise you would have peaks and valleys that doesn't represent correctly the average. there is however a MPG average that you can reset to zero when you take a trip so that only that trip gets picked up. it's in the "on board" menu inside the car data or on the right split screen.

[juhap]

Originally Posted by memphis2012

the concept doesn't make sense, otherwise you would have peaks and valleys that doesn't represent correctly the average.

Not sure what you mean. Let's say you've reset your mileage manually and then you take two trips. On the first trip you drive like you stole your car, so you'll get crap mileage. On the second one you'll let you grandma drive.

Trip #1
100 miles
10 gallons
= 10 MPG

Trip #2
50 miles
2 gallons
= 25 MPG

If the onboard computer simply calculates the average MPG from the MPG of the two trips, it'll be (10 + 25) / 2 = 17.5

BUT if after each trip it simply adds the distance traveled and gallons burned to the total distance traveled/gallons burned, the average MPG is calculated like this (100 + 50) / (10 + 2) = 12.5

The computer only needs to store those two values in its memory and it can always give you an accurate MPG average.

[Rubber Ducky]

Originally Posted by juhap

Not sure what you mean. Let's say you've reset your mileage manually and then you take two trips. On the first trip you drive like you stole your car, so you'll get crap mileage. On the second one you'll let you grandma drive.

Trip #1
100 miles
10 gallons
= 10 MPG

Trip #2
50 miles
2 gallons
= 25 MPG

If the onboard computer simply calculates the average MPG from the MPG of the two trips, it'll be (10 + 25) / 2 = 17.5

BUT if after each trip it simply adds the distance traveled and gallons burned to the total distance traveled/gallons burned, the average MPG is calculated like this (100 + 50) / (10 + 2) = 12.5

The computer only needs to store those two values in its memory and it can always give you an accurate MPG average.

Am certain the second formula is the way it works. Total miles divided by total gallons over the full interval since last reset equals average fuel mileage - 12.5 mpg in your example. My original question is what is the max limit on total miles/fuel before the 'puter start to dump data. Am no longer hoping for an authoritative answer....

[juhap]

Originally Posted by Rubber Ducky

My original question is what is the max limit on total miles/fuel before the 'puter start to dump data. Am no longer hoping for an authoritative answer....

The biggest number a 32-bit computer can store is 4 294 967 296, which should be enough for most of us Not sure if they put 32-bit computers in cars though. I can't think of a reason why there would be some other limit, but that doesn't mean there isn't one.

[Memphis1]

Originally Posted by juhap

Not sure what you mean.

the concept of having the car dump all info at X mileage, rubber ducky asked "at some point the onboard mileage computer dumps earliest data to replace it with current incoming data."

the car maintains three MPGs, you can look at them when you go to car data.

the overall average MPG (no mileage limit, life of the car)

the per trip average MPG, this one resets every time you turn off the car and it goes completely into sleep (20 mins) if you run into a gas station and turn off the car for like 5 mins while you pump gas that doesn't reset it.

the MPG linked to a trip, this one you can reset as many times as you wish and gives you an accurate per trip MPG.

[tiborakos]

Originally Posted by memphis2012

the car maintains three MPGs, you can look at them when you go to car data.

the overall average MPG (no mileage limit, life of the car)

the per trip average MPG, this one resets every time you turn off the car and it goes completely into sleep (20 mins) if you run into a gas station and turn off the car for like 5 mins while you pump gas that doesn't reset it.

the MPG linked to a trip, this one you can reset as many times as you wish and gives you an accurate per trip MPG.

Αre the three MPGs available only on cars with iDrive? because i do not seem to find them anywhere in my car (no iDrive). I can only see one, the same on dashboard and stereo panel....any ideas?