Trip meter inconsistent with total miles

[wilsodg]

I've never reset my trip meter since the car was new, and it's always been less than a mile difference to the total for the car.

I had the Brabus D6S fitted, and when I filled up yesterday (440 miles later) I noticed that the trip is now ~20 miles less than the total for the car - that's almost 5% drift.

Car has done 8600 miles, so very consistent previously.
Any ideas why this should be? I would have thought it all comes from the same source. I can understand the D6S making the OBC MPG wrong, but not the distance travelled..

 

[npuk]

Add on tuning boxes affect the accuracy of the on-board computer, so must have something to do with that.

 

[wilsodg]

I can understand incorrect consumption reported because the tuning box affects fuel delivery, but surely distance travelled just comes straight off the gearbox. I'd have thought trip is just a 'current mileage minus a stored register of whatever the mileage was last time it was reset', so it's illogical for them to drift. No? Which begs the question "which one is correct?" and leads onto.. "if the car doesn't now correctly measure distance, what about speed?"

 

[Black c320]

I agree with what you say,the total and trip mileage should be constant unless reset,it is meaningless otherwise,
unfortunately i don't have a solution, you could try checking the readings over a known distance to try and work out where the error is,
The dealer may be your only option,but dealers are useless if there is no code to tell them what to check.

 

[npuk]

Reset the trip to 0 and make a note of main mileage and see if they run in sync or are still out.

See if BRABUS have had any other reports of this and ask the dealer if there any any software updates for your cluster.

 

[wilsodg]

Thanks, that's kind-of where I've got to - pick driver location sign on quiet motorway and sit at 60mph for ~10 miles and then compare all the results. Driver Location Signs are at 500m intervals with distance to start of motorway accurate to 20 metres, so 32 will equate to 9.94 miles. I'd not realised the significance or use of these till now.