Trip computer questions.
 

A couple of questions about the trip computer thing on my 2.5 Connoisseur SE, the one that displays info on the Alpine radio head-unit thing or on the dash when I press the button on the end of the stalk;
1, How do I reset this? I expected it to reset itself when I zeroed the trip meter, but no.
2, Given that I've not reset it in 500 odd miles, it is wildly optimistic. It suggested that the car was giving in excess of 30 mpg, so I took it very easy to the end of the tank, by which time it was claiming almost 34 mpg!
Thrilled?
I'll say, especially when I calculated using a piece of paper, miles/(litres/4.54) = 24mpg.
Do they all do that?
Or have I got a drunken one?
Or am I doing something wrong?

Thanks in anticipation folks.

Toggle to the MPG and press and hold in the end of the stalk to reset

What type of journeys have you mainly undertaken for those 500 miles Dave? If predominantly motorway cruising then 30 mpg or over is to be expected. The computer is giving your average consumption over those 500 miles.
Was that calculation made using the brim-to-brim method over the same 500 odd miles? I doubt it, otherwise the two figures would be quite close.

Try this: fill the tank until the pump automatically shuts off. Wait five seconds then top it up until it shuts off again. Note the mileage and reset the mpg indicator to zero. Drive until you've used almost the entire tank then repeat the same brimming process and do the calculation. Compare with the figure on the trip computer. They should be within about 1 mpg of each other.

Simon

Following over a decade's discussion on this, it's apparent that 75/ZT OBD computers were calibrated over-optimistically in production. If you want better accuracy, it must be set correctly for the figures to reflect reality. The addendum to my Diagnostic Routine write-up shows you how to recalibrate it. But realise that significant variations in your driving style will skew the results, as will a change of driver. Above all, never reset the system after calibration or you'll lose the benefits of the computer's 'experience' - for want of a better word.


HowTo: https://www.the75andztclub.co.uk/for...ad.php?t=55585


TC

A big thanks for your response.
I've been calculating the mpg of all of my vehicles since 19.10.11. I normally fill my tanks up to the second click of (generally) the same pump at the same garage. I use fuelly.com and it's really to give me an early warning of something about to go wrong. Here's the graph for my 2.5 litre 944.

https://autoshite.com/uploads/monthl...4d8f0ab71e.png

The big drop in mpg was when it was taken off the road for a bit of a re-build and was clearly just shunted about the workshop for a tankful.
It's just odd that the on board consumption things on my XJ-8 and even my Vel Satis gave readings that were broadly inline with proper maths, but the 75 is just having a laugh. It will be used for a daily 26 mile commute over 4 junctions of motorway with dual carriageway at both ends. I'd hoped that it would easily do between 25 & 30mpg.
Am I dreaming?

I'd prefer to see the graph for your Rover KV6. ;)
"Will" be used? :confused: That implies that the Rover isn't being used for that journey at the moment. Can you clarify please Dave.
No; that's a realistic expectation provided that engine service has been carried out diligently and you don't drive as most people do: a cycle of rapid acceleration and heavy braking with no anticipation of the road conditions ahead. :D

Simon

I bought if for the wife to use for her commute on the days when its not fit to use the 944. It needed the belts doing and I've also had the engine oil & transmission fluid changed, a set of plugs, new wipers, the radio sorted and importantly a brand new, undamaged key & key ring.
I drove it a couple of hours home, pottered about in it, sorted a lack of kick down & drove it quite hard for a bit to ensure that it will be utterly reliable for my fair wife. Consequently, the graph is a little disappointing!

https://autoshite.com/uploads/monthl...8961460316.png

This is the reality, the car continues to claim almost 34 mpg!

Dave; are we comparing like with like here? Did you cover 500 miles in the 16 days shown on the graph? Did you fill the tank to the brim on 20th September and 7th October?

Simon

This graph was created before the mpg was reset by holding the button on the end of the stalk? (Or have I missed this being done in subsequent posts)

If it hasn't been reset it will show the average mpg since it was last cleared, which could have been 10 years ago for all you'd be aware.

My own consistently shows 20 per cent less than I actually get. In saying this, others as mentioned can get optimistic displayed claims.

Sent from my SM-A600FN using Tapatalk

The fuelly.com graph tracks just 454 miles and gives an average of 22mpg - it's two brimmed full tanks - the car had three quarters of a tank when I bought it, I couldn't monitor my first fill up as I sent away the IPK? screen to have the lines removed and it reset the trip meter on the dash when it was re-installed.

I haven't reset the trip computer, but it zeroed itself either when the battery was disconnected whilst the timing belts were replaced, or when the head unit was removed & replaced. I suspect the former.

The trip computer, this evening shows;
Trip 2* - 622.6
Range - 521
Average - 33.6 mpg
& Ave speed - 26.2

The distances are far too small for anything meaningful yet, but the disparity is huge.

*I have no idea how to switch between trip 1 (assuming there is one) & trip 2.