OBC calibration re-visited. - BMW Luxury Touring Community
 
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post #1 of 16 Old Jun 11th, 2009, 5:37 pm Thread Starter
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OBC calibration re-visited.

Me and ole Toad used to be pretty anal about checking and verifying gas mileage - usually each tank refill. Until we first started hanging out together, I'd never had a mosheen that got the kinda mileage that the marketing suits said ole Toad would git. Well, they were right and after a few years of keeping tabs (easy to do on the 'puter), we started taking it for granted.

Coupla years ago, ole Toad got the beeg physical and we started checking mileage consumption again. Stoopid me, I put reliance on the OBC, which wuz indicating we were dropping into the low 40 mpg, and below. Lately, it's been showing 36-38!! I'm figgerin' we didn't do such a wonderful job of physical-ing, and ole Toad's age wuz beginning to show; and valve adjustments were needed on the one's that were tight in the past; and the oxygen sensor replaced. OK - we can do all that, and we will, once it gets too hot to ride!!!

Well, why haven't I done this before? What?? Manually check the mileage against the calculator and the OBC. Yeah, what!!! OBC is whacked. Last two full tanks have returned 46.7 and 46.3 mpg calculations. So, we'll be digging out the OBC calibration procedure shortly and getting back in stride with the real world consumption. Just thought I'd post this for folks who may have noticed that this riding season is returning a lower gas mileage than last, and who figger that's life in the LT world. Might not be - might be better than you thought - hopefully. Sure wuz for ole Toad - dang near a 25% correction to the good.

Best regards.
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post #2 of 16 Old Jun 11th, 2009, 6:15 pm
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Re: OBC calibration re-visited.

Just a thought, Dick. Should the BC be recal'd when the battery is replaced or disconnected for some reason? I know a lot of things get reset. Especially the alarm, not that I experienced that.... um it was a real close friend who lives at my house..

Benny C. (Central Texas)
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post #3 of 16 Old Jun 11th, 2009, 6:26 pm Thread Starter
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Re: OBC calibration re-visited.

Quote:
Originally Posted by BennyBob
Just a thought, Dick. Should the BC be recal'd when the battery is replaced or disconnected for some reason? I know a lot of things get reset. Especially the alarm, not that I experienced that.... um it was a real close friend who lives at my house..
Ya know, Benny - I don't know. I wouldn't think so, tho. The book/manual that I have doesn't say anythang about having to do that. Fact, it doesn't even have the procedure for doing it (like it does to reset the TPS). I sure think it wouldn't hurt, but can't believe it to be a requirement, without specifics on when/how to do it. I guess they don't mention it, cuz it doesn't impact the driveability such as the TPS, or - ahem - alarm does. JMHO

And I think I know your close friend!!!
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post #4 of 16 Old Jun 11th, 2009, 6:29 pm
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Re: OBC calibration re-visited.

I have owned a few vehicles with OBC and none have ever been right on fuel mileage. I don't know how the LT works but some work off of the TPS sensor and engine vacuum.

Theres no better way than filling up to the exact same spot every time on the fuel neck and dividing miles to the tenth by gallons to the tenth.

Dave Selvig
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post #5 of 16 Old Jun 11th, 2009, 6:52 pm
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Re: OBC calibration re-visited.

The wife and I (wouldn't dare call her the SO) just returned from an 1100 mile trip to VA beach. We averaged 40.8 mpg on the BC and in actuality mostly slab and pretty well loaded. The speedo is off by 8% according to BC and GPS but the mpg calcs look good.

My $.02
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post #6 of 16 Old Jun 12th, 2009, 7:05 am
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Re: OBC calibration re-visited.

Another factor to consider is seasonal gasoline blends. It's very common to see your mileage drop when the summer blends start showing up at our gas stations. That's because summer gasoline blends contain much less (if any) propane and other light ends. This is done for several reasons, one of which is to keep the RVP (reed vapor pressure) within specs. In the cooler months, the refineries can blend in more light ends (including propanes, butanes which are considered to be somewhat of a waste product in refining) into the fuel, which can actually help to increase mileage. Lots of factors involved of course, but just wanted to remind you about this factor.

As they say, "Your mileage may vary"

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Last edited by Toolman; Jun 12th, 2009 at 9:58 am.
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post #7 of 16 Old Jun 12th, 2009, 9:43 am
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Re: OBC calibration re-visited.

My BC will never show above 42-44 mpg but I usually get in the low 40's. The BC is usually in the mid to high 30's. Don't know why.

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post #8 of 16 Old Jun 12th, 2009, 9:53 am
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Re: OBC calibration re-visited.

Quote:
Originally Posted by ibbones
My BC will never show above 42-44 mpg but I usually get in the low 40's. The BC is usually in the mid to high 30's. Don't know why.
My BC shows about 41 to 44 MPG. On a manual check i get around 46 to 48 MPG's. Now last year at CCR coming outa the mountains the BC showed 96 MPG It's amazing how coming down from 11,000 ft to 7,000 feet in 5 or 6 miles will do for fuel mileage.

Stevie Shreeve
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post #9 of 16 Old Jun 12th, 2009, 9:57 am
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Re: OBC calibration re-visited.

I think whatever ails ole Toad has probably begun affecting my '99 as well. I just tripped 170k this week so maybe its just a bit of oldtimers but I have indeed noticed that the variance between actual fuel mileage and OBC shown mileage has increased somewhat over the past 50k. OBC has always been below actual whether calculated by odometer or GPS.

I don't know about you but that kind of stuff seems to happen to me as I get older as well

Jeff in Myrtle Beach
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post #10 of 16 Old Jun 12th, 2009, 10:26 am Thread Starter
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Re: OBC calibration re-visited.

Quote:
Originally Posted by jeffklt
I think whatever ails ole Toad has probably begun affecting my '99 as well. I just tripped 170k this week so maybe its just a bit of oldtimers but I have indeed noticed that the variance between actual fuel mileage and OBC shown mileage has increased somewhat over the past 50k. OBC has always been below actual whether calculated by odometer or GPS.

I don't know about you but that kind of stuff seems to happen to me as I get older as well
+1, Jeff. Thass why I stay away from mirrors; don't read ingredients list; forgot how to spell 'scales'; and stay both well hydrated and always get the clean plate award. MMMV!!
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post #11 of 16 Old Jun 12th, 2009, 10:36 am
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Dick,

When the fuel tank gets low fill it up!! Ride, Repeat!! Use the OBC for the current temperature and approximately how many miles to empty.

Don Wreyford
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post #12 of 16 Old Jun 12th, 2009, 11:04 am Thread Starter
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Re: OBC calibration re-visited.

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Dick,

When the fuel tank gets low fill it up!! Ride, Repeat!! Use the OBC for the current temperature and approximately how many miles to empty.
Hey, Don - agreed, agreed. Just got tired of that OBC lying to me - it's a distraction in that sense!! We'll be back to R & R shortly. Love ole Toad every time we git on and twist the throttle!!

Ride safe up there in high country, Don.
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post #13 of 16 Old Jun 12th, 2009, 6:08 pm
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Re: OBC calibration re-visited.

Quote:
Originally Posted by katnapinn
My BC shows about 41 to 44 MPG. On a manual check i get around 46 to 48 MPG's. Now last year at CCR coming outa the mountains the BC showed 96 MPG It's amazing how coming down from 11,000 ft to 7,000 feet in 5 or 6 miles will do for fuel mileage.
That does show that the BC depends on engine vacuum for a good bit of the calculation.

Dave Selvig
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2000 Canon Red LT



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post #14 of 16 Old Jun 12th, 2009, 6:50 pm
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Re: OBC calibration re-visited.

Dick... Have you reset the OBC every time you fill your tank? I didn't see that mentioned but I'm sure you did.

Jim S.
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post #15 of 16 Old Jun 12th, 2009, 7:47 pm Thread Starter
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Re: OBC calibration re-visited.

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Originally Posted by jhsonderb
Dick... Have you reset the OBC every time you fill your tank? I didn't see that mentioned but I'm sure you did.
Hi, Jim. Yup, every time. Old habit. That's one of the thangs that got me to doing the manual calc, cuz the OBC wuz showing fewer miles to go after each fill-up. And btw, I pretty much gas up at the same neighborhood station, which has a flat surface surrounding the islands. Always on the side stand, with the bars turned total left.
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post #16 of 16 Old Jun 14th, 2009, 2:35 pm
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Re: OBC calibration re-visited.

My mileage indicator on my 2001 showed in the 20s-30s last year. The bike has 8,400 miles on it. This year the bike wouldn't run. It started and wouldn't keep running without coaxing it with the throttle.
The problem was a spit fuel hose between the pump and filter. The hose had a soft, gummy feel to it. This wasn't the clamp falling off, it was a split at the outer apex of the bend in the line. This line is the only molded piece in the system that has a green stripe on it. I assume it's from a different supplier from the rest? I found a replacement locally, unfortunately it has a green stripe on it.
I found the problem purely by accident. I assumed I had bad gas giving me the trouble. I emptied the tank and then got randomly curious and took out the pump unit to look over the filter. All appeared to be just fine. When I squeezed the tubes, the fuel squirted all over me. I replaced the filter when I replaced the fuel line.
The dealer said the fuel wasn't atomizing, it was dribbling out of the injectors, thus the poor mileage last year and sick running this year. I'd guess this went on for about the past two to three years before it finally let go.
I noticed that the mileage gets reset (and starts recalculating) when you are showing mileage in the OBC and press reset. With no other adjustments, my bike is showing +/- 40 MPG again since the repair.
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