Put 53 (fifty-three !) littres in the Fabia 2 VRS yesterday !

 

It was down to 5 miles range and clearly had the vent nipple pressed down during filling (unintentionally this time).

 

Showed 490 miles range when moving off from the petrol station.  Did 260 mile yesterday and it is still showing about 220 miles left so fairly linear true to original computer prediction.

 

Brisk driving and looks o be about a actual 41 mpg with car showing about 43 mpg.  Pleased overall with all these aspects.

logic says that can't be accurate then... Because the fuel gauge only reads to the top of the tank, so the remaining fuel that is in the tank vent and filler neck are not being measured for your mileage range, so the mpg figures you mention must be wrong becuase you could use say 10 or 12 litres of fuel before the fuel gauge starts even measuing it.

If your Mileometer is accurate by the tyres size you have fitted, or you use GPS.

and you are venting to the same place, and say you travel 450 miles 

then require 45 litres to vent to full again, you achieved 10 miles per litre averaged,  

(or any calculation done with miles done to the litres used, & brimming or Venting.)

or in Gallons. '45.4' and a bitty miles to the gallon.  

 

Simples really, 9-10 gallons in & divide by the miles you get from that.

10 gallons needed to fill again after 370 miles, 37 mile to the gallon over the tank full.

 

Knowing the car, how much goes up the pipe, or how much more goes in venting, doing it week in and week out,

& you get to know your vehicle,  season by season etc.

 

This early on this winter i am back on about 42-45 mpg average when on a long run.

Average while doing short runs without engine getting properly warmed up,

and in the near constant Minus Temps for the past week is 35 mpg.

http://www.briskoda.net/forums/topic/261562-450-miles-in-a-vrs-45-mpg

 

 

george

Lol!

logic says that can't be accurate then... Because the fuel gauge only reads to the top of the tank, so the remaining fuel that is in the tank vent and filler neck are not being measured for your mileage range, so the mpg figures you mention must be wrong becuase you could use say 10 or 12 litres of fuel before the fuel gauge starts even measuing it.

 

The fuel gauge itself is, presumably, a pressure transducer feeding a microprocessor which feeds both the fuel gauge and the range computer with a figure representing the fuel left in the tank via a pressure versus capacity table.  The analogue fuel gauge should roughly be that each eight represents about 5.5 litres but in actuality my gauge does not move for the first 50 miles after a normal fill or 100 to 150 miles from a vented fill.

 

 If driven very conservatively, with a small c, the remaining quarters on the gauge can give about 100 miles each but then this is not what the VRS is designed for so some quick sessions or some cold restarts can bring the mpg down to more like 20-ish mpg and tend to ruin the getting of over 500 miles since the last fill up but 450 is often achieved by me but then I usually do journeys of over a hundred miles and this helps.

 

 The range is calculated using the fuel transducer reading of course which may have ceiling value ie x millimeters of head of fuel but I also am quite sure it take an average, maybe a weighted average, from the two average mpg figures on the display computer but also a third "register" which is unseen to the user may recording just the last few tens of miles.

 

Any road up, very happy with the venting in the Fabia, just hoping someone finds how to do it in the Octy3 else it may affect my future choice.   

The fuel level is measured by a black plastic float on an arm which is attached to a variable resistor, it operates in a similar way to a ball valve in a toilet cistern, the float has a limited range of movement, when it's at it's lowest point there is still a good couple of gallons in the tank, likewise at its highest there is a still fuel above it too.

this resistance is fed to the instrument cluster, along with other data retrieved from the engine ecu via can bus, the engine ecu sends a 'fuel consumption' signal which is based on fuel injection quantity and engine load, road speed etc.. This is all collated by the instrument cluster which then calculates the mpg and range.. So in effect when the fuel is above a certain level it has no way of knowing exactly how much fuel is there so I think you are right in saying it must disregard the fuel level signal and it guesstimates the range based on average data.

they tend to be a bit hit and miss, but th sure fire way of knowing you are going to run out of fuel is the fuel pump becomes noticeably noisier with a whirring type sound when it's pulling air through...

When "vented", all that happens is your Range figure stays at about the same figure for a while.  Best one was filling up just before I got on the Eurotunnel.  Range started dropping just as I cleared Brussels...

& the fuel range very much depends on how you were driving for a bit before stopping to fuel up.

 

If doing a 22 mpg run or the likes or a 53mpg run,

i sometimes vent and then have the Range showing 420 miles & then 460 miles not long after.

On occasion the Range will show something like 340 miles with 11 gallons in the tank.

 

The nice one is setting off with a cold engine with a range like 320,

and once up the road 40 miles or so the range is up over 400.

Again  you get to know what you are liable to get, 

depending on if you are doing a 22 mpg type of drive or a 44 + mpg jaunt.

 

george

 

 

When i filled up 28.4 miles earlier coming off the motorway it was showing 360 mile range,

the next day it did 440 miles from that tank full before putting in another 45 litres.

Totally agree, George - it went from 420 miles up to 460 miles range as I set off along the A16 from Calais and into Belgium; 110km/h constant giving good mpg and flat there as well.  Only dropped to about 400 (and the fuel gauge started to move shortly after) after what was approaching 100 miles into the journey.

 

I've no idea how long the averaging is over - time, distance or a bit of both?

My biggest surprise was the first time on European 100 RON with the vRS,

 & doing 74 miles in an hour, not looking at the Average showing untill i stopped, just watching the Oil Temp

but knowing the fuel was dropping quickish on the gauge, expecting no range left, 

and only managing to getting 45 litres in without venting

Then that was feuled up with 102 RON,  and things got even better the next day.

They really do like the 100/102RON stuff you get in Germany.... Round where I am, it's 100RON from the Shell and 102RON from Aral.

Planning to start using 97ron should I run the tank empty or is it OK to mix the 95 and 96? Draining the tank isn't an option for me.

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Just start using it - it'll be fine with a mix.  It'll take a couple of tankfuls to be "full fat" SUL.

Thanks

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