My infocentre knows exactly how far a mile is - it gets that right - but what it is awful at is the average fuel consumption over a tankful.

What's even more confusing is that the degree of error is completely variable.

On two separate tankfuls - the infocentre said that I had got 34.2 MPG overall. On one of the tanks, I actually got 30.7 and on another just 27.0 - which is over 20% out!

Yet on another tank, the info centre said 33.9 and I got 31.6 - only about 7% out...

Explain how it manages that to me, when it knows exactly how much fuel I've used and how far I've been!

Worst disappointment ever was thinking I'd done 36.5 mpg over a whole tankful only to fill up and find I'd only really averaged 31.9.

Maybe the fact that the computer actually thinks I get a better "instant" MPG doing 80-85mph rather than doing 70-75mpg explains things......
(That's unless someone can come up with some explanation that supports that finding, but I suspect not...)

 

It confuses me on the distance aspect as I would have thought it gets the reading from the same instrumentation as the odometer?

 

.. is about 35miles away, and the trip computer was reporting a trip of just over 20miles.

The trip computer assumes the distance is recorded in kms, therefore 'around' 35 kms (and not the 'around' 35 miles which you have actually travelled). Because the trip computer is set to miles it devides the outcome with 1.6. And there you go, the distance is suddenly 'just over' 20 miles

Of course I am only kidding (I hope)

However, a 20 / 32 ratio is the miles / kms ratio which would make me suspicious about the figures you mentioned. It would certainly made me do some testing with different distance / language settings.

 

Of course I am only kidding (I hope)

However, a 20 / 32 ratio is the miles / kms ratio which would make me suspicious about the figures you mentioned. It would certainly made me do some testing with different distance / language settings.

Yeah I thought the ratio was about the same, from my old Lancia I was used to working in KM. Also to add to that, the cars history is it's last owner bought the car new as a UK car, but then took the car to Germany and registered it there, as he was in the army and based there. So despite being UK supplied and RHD, the car is now classed as an import now it is back in the UK. I am hoping that I missed something and doing the reset (which I found puts the language to Italian too, LOL) It may have resolved it. Guess I will just have to go for a drive tomorrow

 

no real problems but my average consumption on the infocentre consistently shows an extra 2mpg to what i actually get.

 

Just done Newcastle & back. 306 miles, cruising on the motorway at an indicated 80mph in 4h 53m. Trip computer says averaged 62mph.

All of that is absolutely spot on - cos I know exactly how far it is to the office and how long it really took.

So the computer knows the distance exactly. It knows the time taken correctly. It also calculates velocity correctly as "distance/time".

All the "errors" therefore must be in whatever device it uses to measure the fuel used. It says I averaged 38.5 mpg driving with the climate control on (cooling me nicely at 67F on a 25 degree C day).
Wonder what consumption I really achieved?

My previous two tankfuls of petrol both really achieved exactly 30.7mpg - yet the computer says that I achieved 33.6mpg on one and 35.3mpg on the other! Work that one out....

 

My JTD is no different, average reads 49.5 mpg but in reality this is "only" 42 mpg over 10,000 mls.

MPH, distance and time are spot on tho.

Think I can live with 42!

 

Hi there,
just picked up my Alfa Sportwagon 2.4 JTD Lusso yesterday from Newcastle and drove back to London. Sure enough my speedo is in miles and the trip computer adjusts the distance and range to be in mile assuming that the speedo is in KM.
i.e. When the Speedo read 16miles the Trip computer read 10!
Looks like this is a know issue judging by this post.
Is there a simple fix for me to employ? i.e. hold down the button for n seconds click twice.....
Am new to this forum - and look forward to hearing your advice.
Cheers
Nick

 

So the computer knows the distance exactly. It knows the time taken correctly. It also calculates velocity correctly as "distance/time".

All the "errors" therefore must be in whatever device it uses to measure the fuel used. It says I averaged 38.5 mpg driving with the climate control on (cooling me nicely at 67F on a 25 degree C day).
Wonder what consumption I really achieved?

My previous two tankfuls of petrol both really achieved exactly 30.7mpg - yet the computer says that I achieved 33.6mpg on one and 35.3mpg on the other! Work that one out....

it's the same for my car too in that this number is not exactly accurate. however, this could be due how the computer calculates fuel consumption as we step on the throttle. at times if you look at the actual consumption, it can vary from 2.0l/100km to 20.0l/100km depending on how heavy footed we are not sure if this even makes sense at all...

normally what i usually do is to take the distance travelled and amount of fuel i pump to fill 'er up to a full tank to get my consumption

can anyone explain how our onboard computer calculates the fuel consumption?

 

Do you find that if you divide the mpg given by the trip computer by 5 and times it by 8 you get the mpg that you calculate using the manual fill it to the top and reset the the mileage on the main speedo base calculation.
I am pretty convinced it is related to the adjustment being based on trying to convert what it thinks are km's into miles, when in fact what it thinks are kms are actually miles....
cheers

Nick

 

My info centre recently had a funny turn (whilst having the front and back pads changed and front discs) and started reading a much lower distance than i was actualy travelling, turned out to be 5/8 the actual distance. This changed the fuel consumption to be on average 25mpg, for the last 2 or 3 months its been 40mpg (5mpg higher than it actualy was). Like you say by dividing by 5 and times by 8 it would be correct. So i think your right, it thinks that the speedo value is in km.
So then, anybody have a clue how to fix it!?!

 

My thoughts are that it doesn't count the time (fuel) that the car is stationary. So everytime your at the traffic lights or when you start the car in the morning and let it idle to warm up, the fuel burnt isn't used in the calculation. In terms of mpg or for me l/100klm and if your stationary then your not adding to the distance so it's not added to the calculation made. Get what I mean?
In other words when stationary your trip time goes up but your fuel usage doesn't go up because your not moving, hence the ---- in the actual usage indication.
Another reason I think this is true is if you leave your car idling the mpg or l/100klm doesn't change but you are actually burning fuel, and more than you think!

 

Hi there,
just picked up my Alfa Sportwagon 2.4 JTD Lusso yesterday from Newcastle and drove back to London. Sure enough my speedo is in miles and the trip computer adjusts the distance and range to be in mile assuming that the speedo is in KM.
i.e. When the Speedo read 16miles the Trip computer read 10!
Looks like this is a know issue judging by this post.
Is there a simple fix for me to employ? i.e. hold down the button for n seconds click twice.....
Am new to this forum - and look forward to hearing your advice.
Cheers
Nick

Hi, only just caught up on the forum. I posted this originally when I bought the car and found this problem.

There isn't a quick fix, it was a know problem with some speedos giving wrong information to the trip computer. It requires a speedo change which will reset the cars mileage to zero.

 

Hi, only just caught up on the forum. I posted this originally when I bought the car and found this problem.

There isn't a quick fix, it was a know problem with some speedos giving wrong information to the trip computer. It requires a speedo change which will reset the cars mileage to zero.

Hmm - my car is out of warranty - I expect that I'll have to live with this and just do the MATHS! Seems odd that it is a known issue and not something that can be fixed with the travel computer tweaking. Mind you I am new to Alfa's so perhaps I am being too optomistic.

Also re.

My info centre recently had a funny turn (whilst having the front and back pads changed and front discs) and started reading a much lower distance than i was actualy travelling, turned out to be 5/8 the actual distance.

I was told also by the person I picked the car up off that the rear disks had just been changed.....
I think I'll dig a little deeper, and see if there is another cheaper solution.

cheers

Nick

 

My thoughts are that it doesn't count the time (fuel) that the car is stationary. So everytime your at the traffic lights or when you start the car in the morning and let it idle to warm up, the fuel burnt isn't used in the calculation. In terms of mpg or for me l/100klm and if your stationary then your not adding to the distance so it's not added to the calculation made. Get what I mean?
In other words when stationary your trip time goes up but your fuel usage doesn't go up because your not moving, hence the ---- in the actual usage indication.
Another reason I think this is true is if you leave your car idling the mpg or l/100klm doesn't change but you are actually burning fuel, and more than you think!

Quite right, if I spend a lot of time in stop/start traffic, ie. travelling to work every day on the M42, then the infocentre is wildly optimistic, approx 50mpg against the 42mpg I calculate.

But on a recent trip to Scotland with virtually constant motoring it still reported approx 50mpg but I actually managed 49mpg.

 

Hmm - my car is out of warranty - I expect that I'll have to live with this and just do the MATHS! Seems odd that it is a known issue and not something that can be fixed with the travel computer tweaking. Mind you I am new to Alfa's so perhaps I am being too optomistic.

Nick

Still worth a try, as it was a know item they may still replace. My local dealer was fully aware of what the problem was as it was a known recall.

Annoying that you lose the mileage, but I like things to work... Thats why I drive an alfa :cheese: touch wood though all my alfas have been relatively good.

 

EddieGTA,

The problem of your lying computer is because you're driving a right hand model. This model has a longer speedsignal cable, because it has to travel ALL the way to the right of the dashboard. Now the Alfa computer engineers (from what I've heard it's Giuseppe Pastrami, Luigi Gorgonzola and Mario Caprese) that have developed the board computer didn't use a parameter to store the length of the speedsignal cable, but just measured a left hand specimen and punched in the numbers in the computer. When Alfa made clear to the public that they were also going to produce right hand driven models, Luigi, Giuseppe and Mario had a problem......of course.
.
.
.
.
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Sorry, it's late. Don't know exactly where all this bull is coming from. Sorry

 

Still worth a try, as it was a know item they may still replace. My local dealer was fully aware of what the problem was as it was a known recall.

Annoying that you lose the mileage, but I like things to work... Thats why I drive an alfa :cheese: touch wood though all my alfas have been relatively good.

OK, being new to Alfa, perhaps you could give me advise on how I treat the dealers.
Should I ask them to fix the issue as I know it is a know recall? That the car is over 3 years old is not an issue?
Also, I live in Ealing but work in Reading - does anyone have advise as to which Alfa dealer I ought to frequent?

EddieGTA,
The problem of your lying computer is because you're driving a right hand model. This model has a longer speedsignal cable, because it has to travel ALL the way to the right of the dashboard. Now the Alfa computer engineers (from what I've heard it's Giuseppe Pastrami, Luigi Gorgonzola and Mario Caprese) that have developed the board computer didn't use a parameter to store the length of the speedsignal cable, but just measured a left hand specimen and punched in the numbers in the computer. When Alfa made clear to the public that they were also going to produce right hand driven models, Luigi, Giuseppe and Mario had a problem......of course.

Mel, so am I to assume that they didn't test this and that the thing has always been a dud? Seems odd.... Also seems odd that someone's brakes being fixed could trigger this malfunction. I'm sorry I didn't really understand your point about the length of a cable. i.e. if it is ling enough it would still fit and ought to be accurate, if not how does it pick up anything? Perhaps you could explain how you think the figures are derived... I am guessing the computer picks up values for speed, revs and fuel tank volume and does some munging. On mine it is the speed that is consistently 5/8 of the real value - hence the km theory, i.e. real mph getting converted to mph as if they were kph..

cheers

Nick

 

Sorry lost me

 

the fault is with the speedo head unit the trip gets it,s info from the microproccessor in the head, fault is normally the fuel gauge give,s differrent incorrect readings to what is really in the tank. if your still in warranty get it checked out.

 

My infocentre is spot on when it comes to miles and time, but the MPG is consistently between 5% and 10% higher than what I actually get. The funny thing is that it seems to know the amount of fuel left in the tank with a pretty good accuracy, as the range estimate when the tank has only a few litres left in it are very accurate.

 

My thoughts are that it doesn't count the time (fuel) that the car is stationary. So everytime your at the traffic lights or when you start the car in the morning and let it idle to warm up, the fuel burnt isn't used in the calculation. In terms of mpg or for me l/100klm and if your stationary then your not adding to the distance so it's not added to the calculation made. Get what I mean?
In other words when stationary your trip time goes up but your fuel usage doesn't go up because your not moving, hence the ---- in the actual usage indication.
Another reason I think this is true is if you leave your car idling the mpg or l/100klm doesn't change but you are actually burning fuel, and more than you think!

Mine does. If I sit idling, my average consumption increases the longer I am stationary.

 

Quite right, if I spend a lot of time in stop/start traffic, ie. travelling to work every day on the M42, then the infocentre is wildly optimistic, approx 50mpg against the 42mpg I calculate.

Mine does. If I sit idling, my average consumption increases the longer I am stationary.

Now I'm confused

 

I have an idea - wheel size - maybe it's not calibrated correctly to your 17" wheels ...

 

EddieGTA, maybe there is a fault with the Language settings - per a previous post - maybe it's converting everything else except KM to miles ...