Have Honda Jazz (latest model) as a loaner. Built in computer claims 61 mpg but my quick and dirty calculation shows it more like 35mpg (2.5 gall fill up.88 miles later it needs more)

What gives ?

Is this normal ?

My previous experiences with car computer calculated mpg figures found them fairly accurate.

On 25/07/2012 19:36, fred wrote:
Have Honda Jazz (latest model) as a loaner. Built in computer claims
61 mpg but my quick and dirty calculation shows it more like 35mpg
(2.5 gall fill up.88 miles later it needs more)

What gives ?

Is this normal ?

My previous experiences with car computer calculated mpg figures
found them fairly accurate.

Some of them seem to give you a predicted range based on how you are
driving it right "now" rather than based on longer term sampling. We had
a loan car a while back that was similar (so unremarkable I can't even
recall what it was!). But that did a similar trick. Coasted down a road
and it said you were doing 85mpg, gave it some welly and it said 15mpg.
The range prediction seemed to be based on that figure multiplied by the
estimated fuel remaining.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Wed, 25 Jul 2012 19:45:58 +0100, John Rumm wrote:
My previous experiences with car computer calculated mpg figures found
them fairly accurate.

Some of them seem to give you a predicted range based on how you are
driving it right "now" rather than based on longer term sampling.

I managed to get 1.2mpg out of the van yesterday - although that was on
my way home to fix a battery/charging fault, and electrical gremlins seem
to play havoc with its computer system(s). At least the dash display
didn't start up in Spanish this time... :-)

On Wednesday, 25 July 2012 19:36:15 UTC+1, fred wrote:
Have Honda Jazz (latest model) as a loaner. Built in computer claims 61 mpg but my quick and dirty calculation shows it more like 35mpg (2.5 gall fill up.88 miles later it needs more)

Our '56 Jazz' consumption gauge seems to be both accurate overall and sensitive to driving conditions at each moment. We don't see over 55 though, but if it was as low as 35 I'd be looking for flat tyres.

On 25/07/2012 19:36, fred wrote:
Have Honda Jazz (latest model) as a loaner. Built in computer claims 61 mpg but my quick and dirty calculation shows it more like 35mpg (2.5 gall fill up.88 miles later it needs more)

What gives ?

Is this normal ?

My previous experiences with car computer calculated mpg figures found them fairly accurate.


In my experience, there's a lot of variability in when petrol station
pumps decide that the tank is full and cut off. I reckon the variation
is could be up to 2 litres between fills for my car. I'm reasonably
condfident of this, because I've recorded every fuel purchase I've made
in the last 14 years in a spreadsheet and used it calculate MPG... maybe
I need a hobby.

Also, did you fill the tank yourself when accepting the car, or did the
supplier put just enough fuel in it to make the gauge read "full" ?

On 25/07/2012 19:36, fred wrote:
Have Honda Jazz (latest model) as a loaner. Built in computer claims 61 mpg but my quick and dirty calculation shows it more like 35mpg (2.5 gall fill up.88 miles later it needs more)

What gives ?

Is this normal ?

My previous experiences with car computer calculated mpg figures found them fairly accurate.


Did you reset the MPG calc when you got the car? Otherwise, it will show
the average since it was last reset. If previous users were less
heavy-footed ....

On Wed, 25 Jul 2012 23:26:15 +0100 Gb wrote :
Did you reset the MPG calc when you got the car? Otherwise, it will
show the average since it was last reset. If previous users were less
heavy-footed ....

IIRC on my Jazzs the mpg is reset when you reset the trip odo

--
Tony Bryer, Greentram: 'Software to build on',
Melbourne, Australia www.greentram.com

On Wed, 25 Jul 2012 20:00:45 +0000 (UTC), Jules Richardson
wrote:

On Wed, 25 Jul 2012 19:45:58 +0100, John Rumm wrote:
My previous experiences with car computer calculated mpg figures found
them fairly accurate.

Some of them seem to give you a predicted range based on how you are
driving it right "now" rather than based on longer term sampling.

I managed to get 1.2mpg out of the van yesterday - although that was on
my way home to fix a battery/charging fault, and electrical gremlins seem
to play havoc with its computer system(s). At least the dash display
didn't start up in Spanish this time... :-)

Hehe!

I reset the Average MPG on my (brilliant) Torque Pro Android ODB app
and OBD BT dongle and even doing just a few miles it was back up to
around 36 mpg again (it was around 31 mpg when the thermostat was
opening too early and the engine was being overcooled). I think it was
around 38 mpg after a few hundred miles of mixed driving and pre the
reset.

Of course the instantaneous figures are all over the place but the
average seems to fit very closely with the figures seen he

http://www.honestjohn.co.uk/RealMpg/...turer=vauxhall

2004 Meriva A, 1.6i, 36.4 mpg 'real average'.

For the Jazz it shows between 48 and 55 for the Hybrid.
http://www.honestjohn.co.uk/RealMpg/...facturer=honda

Cheers, T i m

Probably used US Gallons in the software... grin.
Brian

--
Brian Gaff....Note, this account does not accept Bcc: email.
graphics are great, but the blind can't hear them
Email:
__________________________________________________ __________________________________________________ __________


"fred" wrote in message
...
Have Honda Jazz (latest model) as a loaner. Built in computer claims 61
mpg but my quick and dirty calculation shows it more like 35mpg (2.5 gall
fill up.88 miles later it needs more)

What gives ?

Is this normal ?

My previous experiences with car computer calculated mpg figures found
them fairly accurate.

On Wed, 25 Jul 2012 19:45:58 +0100, John Rumm wrote:

On 25/07/2012 19:36, fred wrote:
Have Honda Jazz (latest model) as a loaner. Built in computer claims
61 mpg but my quick and dirty calculation shows it more like 35mpg
(2.5 gall fill up.88 miles later it needs more)

What gives ?

Is this normal ?

My previous experiences with car computer calculated mpg figures
found them fairly accurate.

Some of them seem to give you a predicted range based on how you are
driving it right "now" rather than based on longer term sampling. We had
a loan car a while back that was similar (so unremarkable I can't even
recall what it was!). But that did a similar trick. Coasted down a road
and it said you were doing 85mpg, gave it some welly and it said 15mpg.
The range prediction seemed to be based on that figure multiplied by the
estimated fuel remaining.

About 20 years ago I was a passenger in a big BMW that had an analogue
consumption meter. When it was booted hard the needle dropped below zero - I
still haven't worked out the implications of that.
--
Peter.
The gods will stay away
whilst religions hold sway

On 26/07/2012 00:09, Tony Bryer wrote:
On Wed, 25 Jul 2012 23:26:15 +0100 Gb wrote :
Did you reset the MPG calc when you got the car? Otherwise, it will
show the average since it was last reset. If previous users were less
heavy-footed ....

IIRC on my Jazzs the mpg is reset when you reset the trip odo


Yes, it probably varies from car to car. On my Volvo, you specifically
have to tell it to reset the mpg counter. Otherwise, it just goes on
forever.

On 25/07/2012 21:14, RustyCrampon wrote:
On 25/07/2012 19:36, fred wrote:


In my experience, there's a lot of variability in when petrol station
pumps decide that the tank is full and cut off. I reckon the variation
is could be up to 2 litres between fills for my car. I'm reasonably
condfident of this, because I've recorded every fuel purchase I've
made in the last 14 years in a spreadsheet and used it calculate
MPG... maybe I need a hobby.


Sounds to me like you have a hobby :-)

On Wednesday, July 25, 2012 9:00:45 PM UTC+1, Jules Richardson wrote:
On Wed, 25 Jul 2012 19:45:58 +0100, John Rumm wrote:
>> My previous experiences with car computer calculated mpg figures found
>> them fairly accurate.
>
> Some of them seem to give you a predicted range based on how you are
> driving it right "now" rather than based on longer term sampling.

I managed to get 1.2mpg out of the van yesterday - although that was on
my way home to fix a battery/charging fault, and electrical gremlins seem
to play havoc with its computer system(s). At least the dash display
didn't start up in Spanish this time... :-)

No it has a live consumption read out as well as calculated range remaining

On Wednesday, July 25, 2012 9:14:35 PM UTC+1, RustyCrampon wrote:
On 25/07/2012 19:36, fred wrote:
> Have Honda Jazz (latest model) as a loaner. Built in computer claims 61 mpg but my quick and dirty calculation shows it more like 35mpg (2.5 gall fill up.88 miles later it needs more)
>
> What gives ?
>
> Is this normal ?
>
> My previous experiences with car computer calculated mpg figures found them fairly accurate.
>

In my experience, there's a lot of variability in when petrol station
pumps decide that the tank is full and cut off. I reckon the variation
is could be up to 2 litres between fills for my car. I'm reasonably
condfident of this, because I've recorded every fuel purchase I've made
in the last 14 years in a spreadsheet and used it calculate MPG... maybe
I need a hobby.

Also, did you fill the tank yourself when accepting the car, or did the
supplier put just enough fuel in it to make the gauge read "full" ?

Tank was reading empty when I put about 2.5 gallons in. 80-88 miles later I had the orange light on again.

Because its a loaner for an indefinite period whilst my own car is being repaired I was initially loath to fill it.

On Wednesday, July 25, 2012 11:26:15 PM UTC+1, GB wrote:
On 25/07/2012 19:36, fred wrote:
> Have Honda Jazz (latest model) as a loaner. Built in computer claims 61 mpg but my quick and dirty calculation shows it more like 35mpg (2.5 gall fill up.88 miles later it needs more)
>
> What gives ?
>
> Is this normal ?
>
> My previous experiences with car computer calculated mpg figures found them fairly accurate.
>

Did you reset the MPG calc when you got the car? Otherwise, it will show
the average since it was last reset. If previous users were less
heavy-footed ....

Gee folks lets get real he-) Of course I reset the reading. It actually has two readings an A and a B which are independent of each other

In article ,
Tony Bryer wrote:
On Wed, 25 Jul 2012 23:26:15 +0100 Gb wrote :
Did you reset the MPG calc when you got the car? Otherwise, it will
show the average since it was last reset. If previous users were less
heavy-footed ....

IIRC on my Jazzs the mpg is reset when you reset the trip odo

Sounds like very poor design. The two have different functions. Many like
to know the ongoing average fuel consumption.

--
*Where do forest rangers go to "get away from it all?"

Dave Plowman London SW
To e-mail, change noise into sound.

"fred" wrote in message
...
Have Honda Jazz (latest model) as a loaner. Built in computer claims 61
mpg but my quick and dirty calculation shows it more like 35mpg (2.5 gall
fill up.88 miles later it needs more)

What gives ?

Is this normal ?

My previous experiences with car computer calculated mpg figures found
them fairly accurate.

I suspect the only sensible way to test it is fill-er-up, run for a large
number of miles, then fill-er-up again. MPG is miles driven over second
gallons added.

FWIW my Zafira starts blinking the fuel light very early so if that is your
"used all the fuel" indicator, it won't mean "used 2.5 gals".

Paul DS.

Gee folks lets get real he-) Of course I reset the reading. It actually has two readings an A and a B which are independent of each other


Oooops, sorry, my mind reader is in for service. Otherwise, I'd have
been sure to know that.

On 26/07/2012 10:52, fred wrote:

Tank was reading empty when I put about 2.5 gallons in. 80-88 miles later I had the orange light on again.

That's going to be massively inaccurate, easily enough to account for
the discrepancy you're seeing.

In article ,
fred wrote:
Tank was reading empty when I put about 2.5 gallons in. 80-88 miles
later I had the orange light on again.

My BMW has twin tank units to try and give a fairly accurate reading. I
doubt the Honda has.

To be reasonably certain you start from the same point you need to brim
the tank - and I do mean brim - on an absolutely level surface. Even then,
you might expect small errors. The only way to get a good average is over
several tanks. As any filling error gets smaller over a larger quantity of
fuel.

--
*A chicken crossing the road is poultry in motion.*

Dave Plowman London SW
To e-mail, change noise into sound.

On Thursday, 26 July 2012 14:18:57 UTC+1, Dave Plowman (News) wrote:
To be reasonably certain you start from the same point you need to brim
the tank - and I do mean brim - on an absolutely level surface.

Not an issue for the Jazz, because of how low-mounted the tank is.

Also the "low fuel" warning on the Jazz is quite early - 1 1/2 gal at least, maybe more.

In article ,
Andy Dingley wrote:
On Thursday, 26 July 2012 14:18:57 UTC+1, Dave Plowman (News) wrote:
To be reasonably certain you start from the same point you need to brim
the tank - and I do mean brim - on an absolutely level surface.

Not an issue for the Jazz, because of how low-mounted the tank is.

How does that make a difference?

Also the "low fuel" warning on the Jazz is quite early - 1 1/2 gal at
least, maybe more.

Wouldn't call that early.

--
*Procrastinate now

Dave Plowman London SW
To e-mail, change noise into sound.

On Thursday, July 26, 2012 2:02:52 PM UTC+1, Clive George wrote:
On 26/07/2012 10:52, fred wrote:

> Tank was reading empty when I put about 2.5 gallons in. 80-88 miles later I had the orange light on again.

That's going to be massively inaccurate, easily enough to account for
the discrepancy you're seeing.

I dunno. According to the computer I should have been seeing close to 150 miles of usage. 80-88 is a long way off that. I tend to refill as soon as the reminder light flickers so discrepancy there would not be large. Anyway I wouldn't imagine the Jazz has a huge reserve as the tank appears to be very small compared to my usual car

On Thursday, July 26, 2012 10:09:23 PM UTC+1, Andy Dingley wrote:
On Thursday, 26 July 2012 14:18:57 UTC+1, Dave Plowman (News) wrote:
> To be reasonably certain you start from the same point you need to brim
> the tank - and I do mean brim - on an absolutely level surface.

Not an issue for the Jazz, because of how low-mounted the tank is.

Also the "low fuel" warning on the Jazz is quite early - 1 1/2 gal at least, maybe more.

Spec says fuel tank capacity is 42l (Call it 9 gallons) would they really devote 1.5 gallons of that as a reserve ?

On Thursday, July 26, 2012 2:18:57 PM UTC+1, Dave Plowman (News) wrote:
In article >,
fred > wrote:
> Tank was reading empty when I put about 2.5 gallons in. 80-88 miles
> later I had the orange light on again.

My BMW has twin tank units to try and give a fairly accurate reading. I
doubt the Honda has.

To be reasonably certain you start from the same point you need to brim
the tank - and I do mean brim - on an absolutely level surface. Even then,
you might expect small errors. The only way to get a good average is over
several tanks. As any filling error gets smaller over a larger quantity of
fuel.

--
*A chicken crossing the road is poultry in motion.*

Dave Plowman London SW
To e-mail, change noise into sound.

Current BMW computer appear quite accurate. I've had it down to 7 miles range remaining, but at that stage my nerve gave out. Of course it all depends on current driving style and traffic conditions.
Many years ago SMBO's 525 dropped me in the sh1t still showing 17 miles to go

fred wrote:
On Thursday, July 26, 2012 10:09:23 PM UTC+1, Andy Dingley wrote:
On Thursday, 26 July 2012 14:18:57 UTC+1, Dave Plowman (News) wrote:
> To be reasonably certain you start from the same point you need to brim
> the tank - and I do mean brim - on an absolutely level surface.

Not an issue for the Jazz, because of how low-mounted the tank is.

Also the "low fuel" warning on the Jazz is quite early - 1 1/2
gal at least, maybe more.

Spec says fuel tank capacity is 42l (Call it 9 gallons) would they really
devote 1.5 gallons of that as a reserve ?

I don't suppose that they "devote" any of it as a reserve. It's just when
the low fuel light comes on. If you were on some stretches of motorway,
you might be quite glad to get that much warning.


Personally, I think that *accurate* calibrated fuel gauges are long
overdue. I'm sure the reproducibility of the data from the tank senders is
good enough. They just need calibrating.

Tim

fred wrote:

Spec says fuel tank capacity is 42l (Call it 9 gallons) would they
really devote 1.5 gallons of that as a reserve ?

Tank on mine is 64 litres, low fuel warning kicks in at 40 miles
remaining, which at my long-term measured 36mpg is about 1.1 gallons, so
5 litres.

I've taken it a few miles beyond the trip computer's "zero miles" point
and yet only been able to get 59 litres in, which suggests there's more
than 5 litres of extra reserve at the end of the 5 litre reserve.

On 25/07/2012 21:14, RustyCrampon wrote:
On 25/07/2012 19:36, fred wrote:
Have Honda Jazz (latest model) as a loaner. Built in computer claims
61 mpg but my quick and dirty calculation shows it more like 35mpg
(2.5 gall fill up.88 miles later it needs more)

What gives ?

Is this normal ?

My previous experiences with car computer calculated mpg figures found
them fairly accurate.


In my experience, there's a lot of variability in when petrol station
pumps decide that the tank is full and cut off. I reckon the variation
is could be up to 2 litres between fills for my car.

I think this will depend on the car, and the design of the fuel tank.

For example, the length of the pipe between tank and cap. On an original
Mini there's virtually no pipe, so possibility of significant
differences between fill-ups greater. If you're only filling the pipe,
as on (AIUI) most modern cars, less variability.

Rob

In article
,
Tim+ wrote:
Personally, I think that *accurate* calibrated fuel gauges are long
overdue. I'm sure the reproducibility of the data from the tank senders
is good enough. They just need calibrating.

The difficulty is getting an accurate reading when the tank is other than
level. Which of course it rarely is. The shape of the tank will influence
this too.

--
*I yell because I care

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote:
In article
,
Tim+ wrote:
Personally, I think that *accurate* calibrated fuel gauges are long
overdue. I'm sure the reproducibility of the data from the tank
senders is good enough. They just need calibrating.

The difficulty is getting an accurate reading when the tank is other
than level. Which of course it rarely is.

Nothing a little computer chip couldn't do though. I don't expect accuracy
to the nearest ml but it should be possible to get it accurate to the
nearest litre.

The shape of the tank will
influence this too.

You mean the tank changes shape all the time? As long as the tank shape is
constant, then an odd shaped tank isn't a bar to calibration.

Tim

Tim+ wrote:
Dave Plowman (News) wrote:
In article
,

Tim+ wrote:
Personally, I think that *accurate* calibrated fuel gauges are long
overdue. I'm sure the reproducibility of the data from the tank
senders is good enough. They just need calibrating.

The difficulty is getting an accurate reading when the tank is other
than level. Which of course it rarely is.

Nothing a little computer chip couldn't do though. I don't expect
accuracy to the nearest ml but it should be possible to get it accurate
to the nearest litre.

The shape of the tank will
influence this too.

You mean the tank changes shape all the time? As long as the tank shape
is constant, then an odd shaped tank isn't a bar to calibration.

Tim

I remember once having gone SO low the fuel gauge and the trip computer
didn't 'reset' on filling up.


I drove with a gauge at zero, and (-several miles). on the estimated
range display :-)


It finally sorted itself out when I left it parked for half an hour..

That gauge was however normally accurate. But done entirely in software
as was the 'temperature' gauge that always showed 'exactly normal'
temperatures unless the engine was cold. Even when after spending an
hour getting out of a scorching hot car park at an outdoor event, the
rest of the car went into limp mode due to an overheating gearbox and
torque converter.



--
To people who know nothing, anything is possible.
To people who know too much, it is a sad fact
that they know how little is really possible -
and how hard it is to achieve it.

In article ,
Tim+ wrote:
Dave Plowman (News) wrote:
In article
,
Tim+ wrote:
Personally, I think that *accurate* calibrated fuel gauges are long
overdue. I'm sure the reproducibility of the data from the tank
senders is good enough. They just need calibrating.

The difficulty is getting an accurate reading when the tank is other
than level. Which of course it rarely is.

Nothing a little computer chip couldn't do though. I don't expect
accuracy to the nearest ml but it should be possible to get it accurate
to the nearest litre.

I'm not sure why you'd want such accuracy? But twin sensors are a
reasonable compromise. My 15 year old BMW has this.

But of course you've still got the problem of the outlet from the tank.
They don't pick up from the very bottom of the tank to try and prevent
rust etc blocking it.

The shape of the tank will influence this too.

You mean the tank changes shape all the time? As long as the tank shape
is constant, then an odd shaped tank isn't a bar to calibration.

A shallow tank will be more difficult to get an accurate level from than a
deep one.

--
*Therapy is expensive, poppin' bubble wrap is cheap! You choose.

Dave Plowman London SW
To e-mail, change noise into sound.

On 27/07/12 07:54, fred wrote:
On Thursday, July 26, 2012 10:09:23 PM UTC+1, Andy Dingley wrote:
On Thursday, 26 July 2012 14:18:57 UTC+1, Dave Plowman (News) wrote:
> To be reasonably certain you start from the same point you need to brim
> the tank - and I do mean brim - on an absolutely level surface.

Not an issue for the Jazz, because of how low-mounted the tank is.

Also the "low fuel" warning on the Jazz is quite early - 1 1/2 gal at least, maybe more.

Spec says fuel tank capacity is 42l (Call it 9 gallons) would they really devote 1.5 gallons of that as a reserve ?


My Citroën C2 has a 41lt tank. Filling it when the low warning comes on
will take ~35 litres which implies 5-6 litres. The low warning can also
switch on quite suddenly going up a steep incline, at which point it
stays on and the computer say 'fuel too low' in place of the estimated
range remaining. All of which suggests that although the computer is
probably very accurate, the tank level indicator is very approximate.

--
djc

Dave Plowman (News) wrote
Tim+ wrote
Dave Plowman (News) wrote
Tim+ wrote

Personally, I think that *accurate* calibrated fuel gauges are long
overdue. I'm sure the reproducibility of the data from the tank
senders is good enough. They just need calibrating.

The difficulty is getting an accurate reading when the
tank is other than level. Which of course it rarely is.

Nothing a little computer chip couldn't do though. I don't expect
accuracy to the nearest ml but it should be possible to get it accurate
to the nearest litre.

I'm not sure why you'd want such accuracy? But twin sensors
are a reasonable compromise. My 15 year old BMW has this.

But of course you've still got the problem of the outlet from the tank.
They don't pick up from the very bottom of the tank to try and prevent
rust etc blocking it.

That is in fact the actual bottom, where the outlet is,
because you can't get the rest out whatever you do.

The shape of the tank will influence this too.

You mean the tank changes shape all the time? As long as the tank
shape is constant, then an odd shaped tank isn't a bar to calibration.

A shallow tank will be more difficult to get an accurate level from than a
deep one.

On Friday, 27 July 2012 06:54:45 UTC+1, fred wrote:

Spec says fuel tank capacity is 42l (Call it 9 gallons) would they really devote 1.5 gallons of that as a reserve ?

I did 40 miles on the warning light just today. I've done 70.

On Friday, July 27, 2012 10:02:39 PM UTC+1, Andy Dingley wrote:
On Friday, 27 July 2012 06:54:45 UTC+1, fred wrote:



Spec says fuel tank capacity is 42l (Call it 9 gallons) would they really devote 1.5 gallons of that as a reserve ?



I did 40 miles on the warning light just today. I've done 70.

Well the light came on again this morning and range remaining showed 21 miles. I ran it down to 7 miles, and it behaved much as you would expect dropping mile by mile.
I'd brim the damn thing except the repair garage keeps promising to have my car in a few days and as I got it totally empty I'm loathe to leave much in the tank when I return it.
Still don't believe I am getting anywhere close to 60mpg

On Thursday, 26 July 2012 23:56:09 UTC+1, Dave Plowman (News) wrote:
Not an issue for the Jazz, because of how low-mounted the tank is.

How does that make a difference?

The majority of the tank capacity is so far below the filler neck (and the filler neck is narrow) that any variations of fill height in the filler neck make only a trivial difference to total volume.

It's not like some high-mounted tanks where a rapid filling will back the filler neck up with foam (and shut off the nozzle) before the tank is completely full of liquid.

On 27/07/2012 07:45, Tim+ wrote:
fred wrote:
On Thursday, July 26, 2012 10:09:23 PM UTC+1, Andy Dingley wrote:
On Thursday, 26 July 2012 14:18:57 UTC+1, Dave Plowman (News) wrote:
> To be reasonably certain you start from the same point you need to brim
> the tank - and I do mean brim - on an absolutely level surface.

Not an issue for the Jazz, because of how low-mounted the tank is.

Also the "low fuel" warning on the Jazz is quite early - 1 1/2
gal at least, maybe more.

Spec says fuel tank capacity is 42l (Call it 9 gallons) would they really
devote 1.5 gallons of that as a reserve ?

I don't suppose that they "devote" any of it as a reserve. It's just when
the low fuel light comes on. If you were on some stretches of motorway,
you might be quite glad to get that much warning.


Personally, I think that *accurate* calibrated fuel gauges are long
overdue. I'm sure the reproducibility of the data from the tank senders is
good enough. They just need calibrating.

Tim


My 2010 Pug 308 tank sender arm had been 'mis-aligned', probably during
assembly or manufacture, and gave incredibly inaccurate range values and
tank volume. The tank reserve lamp would light up with 16 litres still
left in the tank (of around 60 litre capacity) when it should have been
around 7 litres.

I had to remove the sender and re-calibrate from data obtained regarding
float heights and associated resistances.

Much improved after that.

David

In article ,
Andy Dingley wrote:
On Thursday, 26 July 2012 23:56:09 UTC+1, Dave Plowman (News) wrote:
Not an issue for the Jazz, because of how low-mounted the tank is.

How does that make a difference?

The majority of the tank capacity is so far below the filler neck (and
the filler neck is narrow) that any variations of fill height in the
filler neck make only a trivial difference to total volume.

I'm still not clear how that makes a difference to it being brim full?

It's not like some high-mounted tanks where a rapid filling will back
the filler neck up with foam (and shut off the nozzle) before the tank
is completely full of liquid.

Any such foam won't be around for long. But if you rely on the first time
the pump cuts off, it isn't filled to the brim. Pumps seem to vary in how
early they cut off.

--
*Why is the word abbreviation so long? *

Dave Plowman London SW
To e-mail, change noise into sound.

Andy Dingley wrote:
On Thursday, 26 July 2012 14:18:57 UTC+1, Dave Plowman (News) wrote:
To be reasonably certain you start from the same point you need to
brim the tank - and I do mean brim - on an absolutely level surface.

Not an issue for the Jazz, because of how low-mounted the tank is.

Also the "low fuel" warning on the Jazz is quite early - 1 1/2 gal at
least, maybe more.

My van has two warning lights on it's fuel gauge.

The orange one lights up when low and then it starts to flash when very low.
A bit of experience when running very low shows that putting in 5l of fuel
in just after the flashing starts does not clear the flashing light (ie
within 1 mile of it starting to flash)

On both occassions I only needed enough fuel to get to a petrol station that
would accept my fuel card for a full fill up.


--
Adam