Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Henry Hubbard]

Being a bit of a nerd, I have kept track of my fuel consumption since getting my 2.6 CDX a few months ago. I always fill the tank to the top and mostly at the same petrol pump. When I fill up I also reset all of the trip data. I normally drive with the trip consumption showing because the instantaneous figures go up and down so much with road conditions, and also because I find the occasional 7mpg rather depressing! I had the impression that the actual consumption that I worked out was different from what the display had shown (i.e. lower). I was sure that it said 18.6mpg but the real figure was 16.8mpg.

I have recently done a couple of long motorway journeys, about 300 miles each, using the cruise control most of the way at 70mph. The display showed a trip average of 32.4mpg but the actual figure was 28.6mpg. That is about 10% wrong. I was rather surprised that the meter is that far out. The trip distance corresponds with the mileometer reading but the fuel used does not agree with the petrol station.

I had supposed that the trip computer had access to accurate fuel metering data from the engine management unit but I must be wrong on that. Maybe the fuel metering is done by feedback from engine and exhaust sensors and the system does not actually know the absolute amounts. Maybe the figure is calculated from typical injector characteristics.

Do you know if there is there any way to adjust or calibrate the display?

[freecall666]

i did read on another web page that it can be done  somthing about crossing 2 wires over and pressing the 2 buttons together  and a menu thing comes up but think you can only move it up one diggit and down one diggit, think it sai they set to one standard but can go between 0-3 on settings, but think it depends on the display type.

[Andy B]

I've only ever done a brim to brim fuel check a couple of times but that was years ago. At the time ISTR that the two figures weren't that far out, certainly nothing to lose sleep over. 

[JamesV6CDX]

Being a bit of a nerd, I have kept track of my fuel consumption since getting my 2.6 CDX a few months ago. I always fill the tank to the top and mostly at the same petrol pump. When I fill up I also reset all of the trip data. I normally drive with the trip consumption showing because the instantaneous figures go up and down so much with road conditions, and also because I find the occasional 7mpg rather depressing! I had the impression that the actual consumption that I worked out was different from what the display had shown (i.e. lower). I was sure that it said 18.6mpg but the real figure was 16.8mpg.

I have recently done a couple of long motorway journeys, about 300 miles each, using the cruise control most of the way at 70mph. The display showed a trip average of 32.4mpg but the actual figure was 28.6mpg. That is about 10% wrong. I was rather surprised that the meter is that far out. The trip distance corresponds with the mileometer reading but the fuel used does not agree with the petrol station.

I had supposed that the trip computer had access to accurate fuel metering data from the engine management unit but I must be wrong on that. Maybe the fuel metering is done by feedback from engine and exhaust sensors and the system does not actually know the absolute amounts. Maybe the figure is calculated from typical injector characteristics.

Do you know if there is there any way to adjust or calibrate the display?

Regardless of whether or not the display is lying, those MPG are rubbish regardless..

Only half hr up the road, if you fancy a plug-in...

[Zippy2012]

Being a bit of a nerd, I have kept track of my fuel consumption since getting my 2.6 CDX a few months ago. I always fill the tank to the top and mostly at the same petrol pump. When I fill up I also reset all of the trip data. I normally drive with the trip consumption showing because the instantaneous figures go up and down so much with road conditions, and also because I find the occasional 7mpg rather depressing! I had the impression that the actual consumption that I worked out was different from what the display had shown (i.e. lower). I was sure that it said 18.6mpg but the real figure was 16.8mpg.

I have recently done a couple of long motorway journeys, about 300 miles each, using the cruise control most of the way at 70mph. The display showed a trip average of 32.4mpg but the actual figure was 28.6mpg. That is about 10% wrong. I was rather surprised that the meter is that far out. The trip distance corresponds with the mileometer reading but the fuel used does not agree with the petrol station.

I had supposed that the trip computer had access to accurate fuel metering data from the engine management unit but I must be wrong on that. Maybe the fuel metering is done by feedback from engine and exhaust sensors and the system does not actually know the absolute amounts. Maybe the figure is calculated from typical injector characteristics.

Do you know if there is there any way to adjust or calibrate the display?

Regardless of whether or not the display is lying, those MPG are rubbish regardless..

Only half hr up the road, if you fancy a plug-in...

im half hour in the other direction maybe you could check mine also if everythings clear etc... my mpg meter on a long drive at 70 says 33.4 but on country roads at 50-60 only 23 if im lucky.. but i only did 378miles to a full tank & filled up yesterday & put in 71ltrs....

[2woody]

there's a couple of things here......

the MPG meter reads only the fuel injector open time, vehicle speed and tank level, but the latter is very heavily damped.
For instance, when you fill up, it takes a while before it takes that full figure into its memory.

secondly, it averages the figures over the last 200 miles. So if you flatten the memory, it gives it a bit of a problem. Likewise if your "trip" extends over 200 miles.

[duggs]

Hmmmm !     Tuesday, Ipswich to Ashford, Kent and back, driving like Miss Daisy (60-70 mph) in my 3.0 Elite...36.4 MPG average over 280 miles.

Based on a fill up before and after....it seems fairly accurate to me......not least the fact that I was well chuffed.

Used £52.00 of fuel for which I get back £126.00 for "business miles" !   NOT everyday I actually make money using my car for business use.

[marrus69]

wow thought mine was good at 24.4 but its bad,would bank 2 sensor 1 not working make a diffaranc.having new one fitted tommorow

[dbug]

i did read on another web page that it can be done  somthing about crossing 2 wires over and pressing the 2 buttons together  and a menu thing comes up but think you can only move it up one diggit and down one diggit, think it sai they set to one standard but can go between 0-3 on settings, but think it depends on the display type.

Another Rustyism 

[freecall666]

found it,

Short pins A and D on the diag plug.
Switch on the ignition.
 Calibration of Range
D5
If you feal the range is not accurate you can adjust it.
Deviations of upto 3 litres can be adjusted for in 0.5 litre steps.
When correctly adjusted, the car should drive for 3 to 6 miles  before it runs out of fuel.

Select mode D5.
Press the hours pin.
A: should be displayed next to a positive or negitive even number, this is followed by the range @ 28mpg.

The range can be adjusted from –A12 to A0 to +A12.
If the display says you have miles left and you believe you are about to run out of fuel then it should be adjusted in the negitive dirrection.
If the display says you have 0 miles to travel yet you can drive over 6 miles then you should adjust it in the positive direction.

Use the mode button to select the A value you require. Then hold the raised button until - - - is displayed.

The fuel signal comes from the ecu. On V6 models this is across injector 1.

[Entwood]

found it,

Short pins A and D on the diag plug.
Switch on the ignition.
 Calibration of Range
D5
If you feal the range is not accurate you can adjust it.
Deviations of upto 3 litres can be adjusted for in 0.5 litre steps.
When correctly adjusted, the car should drive for 3 to 6 miles  before it runs out of fuel.

Select mode D5.
Press the hours pin.
A: should be displayed next to a positive or negitive even number, this is followed by the range @ 28mpg.

The range can be adjusted from –A12 to A0 to +A12.
If the display says you have miles left and you believe you are about to run out of fuel then it should be adjusted in the negitive dirrection.
If the display says you have 0 miles to travel yet you can drive over 6 miles then you should adjust it in the positive direction.

Use the mode button to select the A value you require. Then hold the raised button until - - - is displayed.

The fuel signal comes from the ecu. On V6 models this is across injector 1.

So .. if what you say works .. you have just calibrated the RANGE function .. ie . the number of miles the computer thinks you can do on the fuel in the tank.

This has ABSOLUTELY NOTHING to do with the thread which is about fuel CONSUMPTION .. the miles per gallon function of the system .....

What you've done is a bit like giving a guy with a puncture instructions on how to change his oil ....  perhaps factually correct ... but as usefull as tits on a bull.

[davethediver]

found it,

Short pins A and D on the diag plug.
Switch on the ignition.
 Calibration of Range
D5
If you feal the range is not accurate you can adjust it.
Deviations of upto 3 litres can be adjusted for in 0.5 litre steps.
When correctly adjusted, the car should drive for 3 to 6 miles  before it runs out of fuel.

Select mode D5.
Press the hours pin.
A: should be displayed next to a positive or negitive even number, this is followed by the range @ 28mpg.

The range can be adjusted from –A12 to A0 to +A12.
If the display says you have miles left and you believe you are about to run out of fuel then it should be adjusted in the negitive dirrection.
If the display says you have 0 miles to travel yet you can drive over 6 miles then you should adjust it in the positive direction.

Use the mode button to select the A value you require. Then hold the raised button until - - - is displayed.

The fuel signal comes from the ecu. On V6 models this is across injector 1.

So .. if what you say works .. you have just calibrated the RANGE function .. ie . the number of miles the computer thinks you can do on the fuel in the tank.

This has ABSOLUTELY NOTHING to do with the thread which is about fuel CONSUMPTION .. the miles per gallon function of the system .....

What you've done is a bit like giving a guy with a puncture instructions on how to change his oil ....  perhaps factually correct ... but as usefull as tits on a bull.

Good old rusty

[noel]

found it,

Short pins A and D on the diag plug.
Switch on the ignition.
 Calibration of Range
D5
If you feal the range is not accurate you can adjust it.
Deviations of upto 3 litres can be adjusted for in 0.5 litre steps.
When correctly adjusted, the car should drive for 3 to 6 miles  before it runs out of fuel.

Select mode D5.
Press the hours pin.
A: should be displayed next to a positive or negitive even number, this is followed by the range @ 28mpg.

The range can be adjusted from –A12 to A0 to +A12.
If the display says you have miles left and you believe you are about to run out of fuel then it should be adjusted in the negitive dirrection.
If the display says you have 0 miles to travel yet you can drive over 6 miles then you should adjust it in the positive direction.

Use the mode button to select the A value you require. Then hold the raised button until - - - is displayed.

The fuel signal comes from the ecu. On V6 models this is across injector 1.

So .. if what you say works .. you have just calibrated the RANGE function .. ie . the number of miles the computer thinks you can do on the fuel in the tank.

This has ABSOLUTELY NOTHING to do with the thread which is about fuel CONSUMPTION .. the miles per gallon function of the system .....

What you've done is a bit like giving a guy with a puncture instructions on how to change his oil ....  perhaps factually correct ... but as usefull as tits on a bull.

but as usefull as tits on a bull.

[Henry Hubbard]

The advice on adjusting the remaining range is very interesting. However, I think it is for calibrating the fuel tank sensor, whereas I think that I need to calibrate the injector. It does seem to be a very detailed description of the procedure so you seem to have found a good source. I would be interested to hear where you found this information, as it seems likely that there is a similar procedure to adjust for injector characteristics.

I suppose that I could just try pressing a different button to see if that invoked a different function. Failing that, it may be that I need to use a different pin on the diagnostic socket but without knowing which one then I am sure to make a very expensive mistake, so I'll not try that.

[zirk]

Probably worth checking that you have the right MID for the Car first, in case its been swoped at some point in its life for missing pixels etc.

Press and hold both buttons on the stalk for a few seconds should bring up a table on the MID, the table can be cross referenced as to what the MID has been programmed for, ie, Engine, Gearbox, Wheel type etc. fairly sure the table info is on this site somewhere.