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-   -   Accuracy of on board trip computor (http://www.jeepgarage.org/f5/accuracy-of-on-board-trip-computor-4647.html)

nav18tor 12-09-2009 01:35 PM

Accuracy of on board trip computor
 
Has anybody else noticed a huge variance in the OBC trip MPG?

Bacause I do at least 1000 miles a week, fuel consumption is high on my list of things to watch

This being my 2nd CRD WK I was not overly concerned as I can always get 30 showing on the trip (OBC) and thats US with UK being even better but not able to display

However..........

My last fill up I actually checked the odo reading and zero'd at the fill up today

The OBD is showing 31.7 mpg for the exact period/mileage but the long hand mathmatical calculation reveals a very different result

A real (US) 23.6 against the OBD @ 31.7(US)

Also checked my odo against a GPS tracking system and it shows to be 1% out, not enough to throw up that kind of difference

What gives:eek:

DJ BoNiOmArIo 12-09-2009 01:41 PM

Re: Accuracy of on board trip computor
 
you sure you did the calculations right?

also idling and accelerating stop and go traffic play a big factor w/ mpg ...

what kind of road do you travel on?

anyways I do not find that surprising because mine is actually opposite of that lol my obc shows lower mpg than what I'm really getting

Scottina06 12-09-2009 01:52 PM

Re: Accuracy of on board trip computor
 
I try not to even look at mine.....LOL

nav18tor 12-09-2009 02:17 PM

Re: Accuracy of on board trip computor
 
I will concede, I am going to check this over the next few tankfulls!!

I am certain the figures I am working with are correct, I did 327.5 miles according to the trip, I filled up and it took 53.55Litres which is 11.77 UK gallons, simple calculation of 11.77 divided by 327.5 = 27.82 (UK) mpg or 23.16 (US) mpg

This is the 3L CRD driven 90% on motorway (highway) at between 60- 80 mph traffic allowing with no serious use of acceleration and very little town work

It is also "chipped" which on the previous CRD lifted mpg by 10% and on this one the OBD shows a 5% improvement

The tyres are run at 38PSi as opposed to the factory setting of 33, no roof rails, AC is always on, I don't sit with the engine idling I always switch it off

blackpepper 12-09-2009 02:20 PM

Re: Accuracy of on board trip computor
 
The one time I did a full tank calculation, my evic was only .1 mpg off from what I calculated.

nav18tor 12-09-2009 02:49 PM

Re: Accuracy of on board trip computor
 
I am going to check, check, and check again

My WK is fitted with a real time tracking device that I can veiw and check mileage/speed and alsorts of other interesting stuff so I will be able to verify the mileage

Thats how I know the odo reading is 1% off, the tracking is way more accurate than the odo

I can also confirm that my top speed today was 80 mph and that was only for a couple of miles!!

DJ BoNiOmArIo 12-09-2009 03:25 PM

Re: Accuracy of on board trip computor
 
seems like you have done ur hw ... makes you think how smart are the people who actually do the evis programming :)

nav18tor 12-09-2009 03:39 PM

Re: Accuracy of on board trip computor
 
Quote:

Originally Posted by boniomario (Post 114268)
seems like you have done ur hw ... makes you think how smart are the people who actually do the evis programming :)

I hope I am wrong, 23mpg from a oil burner is not good............

B.P.O.D 12-09-2009 04:13 PM

Re: Accuracy of on board trip computor
 
they way i do it is following:

fill gas tank
reset computer trip
when jeep gets to empty i divide the miles/gallons of gas i put in

DJ BoNiOmArIo 12-09-2009 04:53 PM

Re: Accuracy of on board trip computor
 
Quote:

Originally Posted by nav18tor (Post 114284)
I hope I am wrong, 23mpg from a oil burner is not good............

yes that is no bueno I get that with my 3.7L on the highway :D that's right b1tches lol

Quote:

Originally Posted by B.P.O.D (Post 114323)
they way i do it is following:

fill gas tank
reset computer trip
when jeep gets to empty i divide the miles/gallons of gas i put in

thanks genius that math was real hard to do j/k lmao :D

blackpepper 12-09-2009 04:55 PM

Re: Accuracy of on board trip computor
 
I get 23 mpg on the highway with a 2% grade, following an 18 wheeler, with a slight tail wind... bitches :D

nav18tor 12-09-2009 04:56 PM

Re: Accuracy of on board trip computor
 
I think the best thing I can do is ignore it

I like the Jeep so much, its not an issue:)


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