This makes no sense (trip computer)

[rbrocky]

Ok, someone tell me where I am going wrong.

The petrol light on my clio comes on at around 25-30 miles left. saying I have used around 12.2 gallons of fuel (The same every time after I have reset the trip after totally brimming it.

I head to a petrol station and cannot fit more than 51ish litres in the tank.
Surely 51 litres is 10.2 gallons? Where is this supposedly extra 2 gallons usage came from, as the tank will only let me put in 10 gallons not 12 that I have "used". Or am I being really stupid?

Thanks

 

[Chris197F1]

51L is 11.4 gallons isnt it?

EDIT - its 11.2 (4.54 Litres to a gallon)

 

[rbrocky]

isn't it 5l = 1 gallon?

 

[Chris197F1]

not according to Google, its 4.54

 

[rbrocky]

I see! But still, where is the extra fuel usage coming from

 

[Foxspeed]

it is 4.54lts = 1 gallon

as for the clio trip computer its only a "guide" - it is also taking average readings and continuosly re-calculating the figures

also dont forget if you "brim" the tank you are also filling the filler neck so in theory put more fuel in and this can also alter the figures

i have checked mine several times and the fuel consumption (dash display) is always more than actual used...

 

[rbrocky]

But the pump still says how much you have put in @51l.

Stupid french cars...

 

[Foxspeed]

But the pump still says how much you have put in @51l.

Stupid french cars...

so thats 11.2 gallon in a 12 gallon tank....so 0.8gallon left!

the computer says you have used 12.2 so like mine its over reading on fuel used - is it not?

and if your brimming it your also filling the filler neck and that will screw the calculation!

(you can also do 51 x 0.22 = gallons)

 

[rbrocky]

Yeh i suppose there will be around .8gal left. But if you reset it when you fill up (Regardless of how much you fill up). Then use the exact same again it should read the figure that you have filled up? it shouldnt matter if you have filled it up the feedneck or not.

 

[ado]

So the light came on and you filled it up?

11G + 1G left to do that 30+ miles.

BTW if its been brimmed it should run out just before 13G indicated.

 

[Robo_#1]

If you forget about what's left in the tank (as we don't know how much fits in the filler neck), and just look at the usage. The Gallons consumed should = exactly the amount you can fit back in to your tank, but I would image its a figure calculated by injector usage which I'd guess isn't perfect. Also when your filling up and the pump 'clicks' a lot of the time its because there's an air bubble causing some back pressure on the pump, give it a second to settle and you can easily squeeze more fuel in, so that's far from an exact science, so each time you fill up you can easily vary the amount you put in to the 'click'.

+ It's French electronics, lets face it, its never going to be right.

 

[Dean Mac]

51L is 11.4 gallons isnt it?

EDIT - its 11.2 (4.54 Litres to a gallon)

I agree.

 

[rbrocky]

Robo thats the point I was trying to get across. The amount consumed should equal the amount going in at the pump. But its over reading, I suppose you are right about the french electronics

 

[dh6]

Don't believe the pump either. Like everything they have a calibration range and obviously the density of the fuel will change with storage temperature too. That 40 litres on a summer afternoon has a lower amount of energy in it than first thing on a cold morning!

 

[Robo_#1]

Fuel pumps weights and measures tolerances are -0.5% / +1%. or in plain English you can get anywhere in between 0.995L (-5ml) and 1.01L (+10ml) per litre of fuel from the pump.

 

[Gorms]

Most fuel pumps will only operate within that range when there is an ambient air temp of 20°c.

 

[930Tech]

The last track day i did i filled up my 20 litre fuel jug at a local station and when it got to the 20ltr mark the pump said 19.2 litre.

How does that work? i thought i'd gained some.

It was done dry at the start.

 

[matt_brown_92]

I don't mean to change topic, but my trip computer, when I turn off TC says, ASP/ESR (or something) DESACTIVATED. Surely that can't be a typo??

 

[Andreas187]

I agree mine is also a bit wrong. It's not the fuel pump because weights and measures is far too strict to allow such discrepancies. Even when the trip said I used just 15 litres I could only put in 14

 

[Foxspeed]

if you expect it to be 100% accurate then dream on.....

too many variables that effect the readings!