Accuracy of OBC "Range" function..

[volfman]

Hey guys,


Drove my car to when the gauge got to about 17 miles left, and I wanted to know how low you guys have gone because I want to know how accurate that thing is...

Thanks.

[Anfanger]

I don't know for sure, but if the engineers had any common sense they calibrated it to have higher accuracy on lower numbers. I think it is probably pretty accurate down to +/- a mile.

[///M LIFE©]

I drove it down to 9 miles then it flashed 'empty' thats when i deicided it was a good idea to fill up :D

[Kevlar]

It's not that accurate... I never run my tank down below 1/4 (bad for the fuel pump and all).

I've seen people run out of gas with 25-30 miles left on the OBC and I've also seen people still driving with 0 miles displayed on the OBC.

Why would you want to run your tank down to bone dry anyway?

[EstorilBlauM3]

Originally posted by Kevlar
It's not that accurate... I never run my tank down below 1/4 (bad for the fuel pump and all).

I've seen people run out of gas with 25-30 miles left on the OBC and I've also seen people still driving with 0 miles displayed on the OBC.

Why would you want to run your tank down to bone dry anyway?

Agreed. The range function on the OBC isn't that accurate. It is bad for the fuel pump to run your tank completely empty. When I have about 1/4 left, I fill it up. I mean, I eventually have to do it so I just do it to get it over with.

[JoeZ]

Originally posted by Kevlar
It's not that accurate... I never run my tank down below 1/4 (bad for the fuel pump and all).

I've seen people run out of gas with 25-30 miles left on the OBC and I've also seen people still driving with 0 miles displayed on the OBC.

Why would you want to run your tank down to bone dry anyway?


I've also read some stories about people running out of gas with the OBC still showing that there are miles left. I don't really pay attention to the OBC too much but I've never seen it go below 50 miles or so left.

[mr happy]

Well the lowest i had on my OBC was 7 miles, because i was stuck in traffic for 2 hours.

kinda scare that i had to push the car to gas station. close call

[BMWMPOWER1996]

as the engineer told me, the range is very accurate on newer cars, the older ones are still pretty accurate...you can run it pretty low and its pretty accurate...you drive a bimmer dont starve it..put some gas in it!

[volfman]

Haha I know, I know. There just weren't any gas stations on the 17 freeway, thats all. I usually fill it up at 1/8 of a tank anyway.

[umnitza]

I fill up when the thing is red:)

In reality, I've run the car to almost 0, and a friend ran it to 0 and was able to drive another 2 miles with no adverse affects.

The OBC is better used when you use the hidden features and get exact Liters remaining.

It's option 7 in the hidden (full obc only) display.

[Dinan330ic]

hidden features??? Tell me more about these. I didn't know of any hidden features.

[volfman]

http://www.unofficialbmw.com/repair_faqs/obc.html

Just found out about these myself from umnitza. Tried them - they're pretty sweet. You have to unlock your OBC first.

[AaronM3]

the secret functions thing is just tight.


as for the range thing.. i ONLY use that as a general guide. I always fill up with about 20 miles +- remaining on it. No way in hell i am letting my m3 sit on the side of some road while I go get gas. You'll come back to pieces of a car, guarenteed. There are " vultures" as we call them.... that all day long circle DF/W looking for dead cars to go vandalize.

[Dinan330ic]

that's siiiiiiiiiiiiiiiick!!! Thanks

[wicked]

Sweet cool link
I woulod try it but i don't want to mess anything up. My luck i would screw it all up.

[BMW325i]

I don' think its very accurate. I mean the range is basically based on your speed so as your speed fluctuates so will the range. If you are just crusing on the freeway, then it would probably be accurate but in stop and go everyday driving I wouldn't trust it. I don't. Its funny when I look at it and it says 20 miles and then a quarter of a mile later it goes to 19 and continues to fall and I'm like wtf. Anyway, I wouldn't trust it.

Jeffrey

[makken]

I've heard that the OBC range function is calculated so that you can still drive 15 or so miles when it displays zero. No way in hell i'm going to test it though.

I've had some werid stuff happen with the range function before. It would be at 120 when I turn off the car in the parking lot, and when I come back, it'll display like 140 or so. Also, one time (at band camp :)) It displayed 80 or so, but then, one city block later, it dropped to 17, then down to 11, then to 9. I immediately stopped at the local gas station, put in $5 worth of gas (about 2 gallons), and when I turned the car back on, the gas gauge went to half tank (from empty), and range went to 110 or so.

[FiveEight]

I've run mine to below 0 before. It just started flashing dashes: "--------" It totally snuck up on me and I got pretty scared and started coasting as much as I could. I probably went 5-10 miles after it was at 0. I apologized a lot to her for it. I almost always fill up at 1/4 a tank too, just not that time. I never knew why I did it @ 1/4 tank, someone just told me to do it so I did and haven't ever wondered why... You learn something new everyday, thank you bf.com!! :D

[volfman]

You should now all use option '7' in the secret functions of the OBC. I'm pretty sure that's way more accurate than your range function, as this one displays how many liters of fuel you have left in your tank.

Another cool feature is your current speed in km/h. Anyone know if that's more accurate than your speedometer? In other words, since the speedometer stops being accurate @ ~ 100mph, will the km/h secret function of the OBC continue to be accurate?

:) Thanks.

[umnitza]

I believe speed in km/h has the same accuracy as your speedo and has the same "fudge" factor.

I think it's tied directly to it:)

[abakos]

My OBC is fyorked up...it's been telling me I get like 46 mpg on the highway. Needless to say, I'm not.

Is there any way to reset these things or recalibrate?

[FiveEight]

I know my obc is different than my speedo at least on speed because, when I reset the average speed (if I'm going at about a constant speed, like with the cruise set) it is always a little higher on the speedo than it is on the obc. It's around a 3-5mph difference. I wonder which one is right.