MPG Correction Using Xentry

[shertex]

So, on my CDI, over the course of 11,000 miles or so the computer said I was getting 35.2 mpg. But actual measurements, logging every tankful, told a different story: 31.9 mpg.

In Xentry, there's a place to introduce a correction factor as a percentage. Here's the exact language:

The consumption figure displayed increases if positive values are entered.
The consumption figure displayed decreases if negative values are entered.

That seems a little ambiguous since HIGHER mpg is LESS consumption...but what else than the mpg figure could they mean by "consumption figure?" I'm assuming they mean in my case to enter a negative number. So I entered -10.

Still in the early going....but on a 85 mile mostly highway trip it says I got 41.9 mpg. There's not a chance that's correct. But we'll see where things stand when I next fill up.

Anyone else try this? Have you been able to get it right?

[ROLLGUY]

I am with you, it makes sense to input a -number. I have been wondering why my indicated MPG is always MORE than actual. The indicated is always a generous amount (I would call it), when I would be happier if it was a little stingy (telling me less than I am actually getting). Could that be why they advertise these cars getting 27 & 37? I get on the average 29 combined, and have gotten up to 39 with mostly highway driving. All these posts about the Xentry are making me want one!

[shertex]

Originally Posted by ROLLGUY

I am with you, it makes sense to input a -number. I have been wondering why my indicated MPG is always MORE than actual. The indicated is always a generous amount (I would call it), when I would be happier if it was a little stingy (telling me less than I am actually getting). Could that be why they advertise these cars getting 27 & 37? I get on the average 29 combined, and have gotten up to 39 with mostly highway driving. All these posts about the Xentry are making me want one!

It really is pretty cool. I told my wife, "It's an investment...it will save us money in the long run." She's not so sure, thinking it more likely that it will COST us money in the long run!

[ROLLGUY]

Originally Posted by shertex

It really is pretty cool. I told my wife, "It's an investment...it will save us money in the long run." She's not so sure, thinking it more likely that it will COST us money in the long run!

Well, just visiting a dealer or indy for a diagnosis a couple times will pay for the tool. Having the EPC is a bonus as well.

[Frank Reiner]

Originally Posted by shertex

In Xentry, there's a place to introduce a correction factor as a percentage. Here's the exact language:

The consumption figure displayed increases if positive values are entered.
The consumption figure displayed decreases if negative values are entered.

In the rest of the world, consumption is expressed as:
Litres per 100 kilometers>L/100km
It is the reciprocal of distance per litre, or miles per gallon.

Hence, entering a positive correction factor will result in a displayed reduction of miles/gallon (1/miles/gallon=gallons/mile, which is the form of the correction).

[shertex]

Originally Posted by Frank Reiner

In the rest of the world, consumption is expressed as:
Litres per 100 kilometers>L/100km
It is the reciprocal of distance per litre, or miles per gallon.

Hence, entering a positive correction factor will result in a displayed reduction of miles/gallon (1/miles/gallon=gallons/mile, which is the form of the correction).

That makes sense....so looks like I got it backwards.

[EDBSO]

Interesting, I checked mine and after 6,451 miles using the math I got 35.15 mpg and the computer thought I got 35.4 which is remarkably close to the actual number.

I have heard that the computer can be significantly off and was pleasantly surprised that it was so close to the actual figure.

39.5 mpg was the highest mpg tank on the trip 33.2 was the lowest.

[MB_FanAddict]

Thanks to Frank Reiner I think we've figure it out! I tried a negative 6% value a few weeks ago, but found the displayed mpg about the same or slightly higher!
I thought maybe it just needed a larger correction value, but in fact I had it backwards.

I decided to try again and entered a positive 6% value last night and watching the display while driving today, noticed the mpg shown was lower! Looking
back through my records, I've seen between a 4-8% discrepancy between the displayed and actual fuel milage with the default setting for the OM648,
so hopefully a 6% correction will greatly improve the accuracy.

Originally Posted by shertex

That makes sense....so looks like I got it backwards.

Originally Posted by Frank Reiner

In the rest of the world, consumption is expressed as:
Litres per 100 kilometers>L/100km
It is the reciprocal of distance per litre, or miles per gallon.

Hence, entering a positive correction factor will result in a displayed reduction of miles/gallon (1/miles/gallon=gallons/mile, which is the form of the correction).

[shertex]

Changed mine to +10 and now it seems perfect.

FYI it will recalculate all the old data if you choose to leave it intact. In my case, I erased the 11,000 miles so am starting fresh.