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  • On dash fuel usage meter

    Who else finds the on dash fuel meter (litres per hundred km very erratic) ? .I find that unless i continuously keep reseting it every time I go for a drive after the engine has warmed up ,the usage is out by at least 2 litres(manual mode).Also whilst in auto mode it shows 12-12.4 most of the time and my figures show between 11.2 - 10.7 .
    2007 DID AUTO

  • #2
    Dumb Question, but I was looking at the same thing tonight and I realised that the consumption scale on mine goes from 0 down to 20 not 0 up to 20 as per the manual (See pg 3-24). Ie swap the numbers 20 and 0 as they are in the manual and that is what mine looks like. What is the scaling like on every body elses??
    Dan C; Stock NS Exceed DID Auto w T'bar, Magellan Explorist XL w DAST topo, Tom Tom One

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    • #3
      yep i have always thought that it is pessimistic, did a manual calc once over a full tank and got 1 litre/100 better result.

      also noticed that it does seem erratic at times over a long trip that i take regularly ..
      SWB NT X DiD its R E D

      SWB NS X DiD that's double D's !! Retired

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      • #4
        I have 0 at the top, and either 20 or 30 (depending on whether one of the 5 min points averages >20L/100km (usually when you are still starting out and then immediately get stuck in traffic - then the scale changes). On average though I always reset "manual" and "auto" fuel consumption modes after each refill, and record the computer reading compared to actual fill. I have done this since I got it, and so I can say with some accuracy, that over the last 5700 km my LWB Auto is getting around 10.6 - 10.7 L/100km, yet the car's reading of average fuel consuption over this distance would lead me to assume I was doing 11.4 to 11.5 L/100km. Thus, I have the computer readout at about three quarters of a litre higher in fuel consumption than reality.

        In terms of erratic readings, as the car does seem to go through more fuel when cold this expains some of the very high early values, and as the manual reading calculates from a smaller set of drive time, it will start to differ from the auto reading as the days wear on, which always shows the last 4 hours of actual drive time (except when reset).
        Mar07 build NS LWB VRX Auto

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        • #5
          Don't forget that the reading on the dash is only an average and isn't meant to be an actual figure. From memory the computer only takes a reading every 30 seconds or so to come up with the average. Therefore if you're sitting on 10l/100km when it takes the first reading, then floor it and use 20l/100km for the next 29 seconds, then drop back to 10l/100km as it takes the next reading, the two readings the computer takes are both 10l/100km making the average 10l/100km. The actual usage would obviously be marginally higher which adds up over a whole tank.
          2010 150 Prado GXL V6 Auto

          Accessories fitted: BFG At 275/65/R17, Rhino Platform Rack, Toyota Cargo Barrier.

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          • #6
            Originally posted by danc12 View Post
            Dumb Question, but I was looking at the same thing tonight and I realised that the consumption scale on mine goes from 0 down to 20 not 0 up to 20 as per the manual (See pg 3-24). Ie swap the numbers 20 and 0 as they are in the manual and that is what mine looks like. What is the scaling like on every body elses??
            It depends on whether you have it set up to display Litres/100km or Km/Litre.
            Mike R. Sydney. Pajero GLS NX Silver Jan15. DiD Auto. STILL grossly disappointed with the errors in Speed Limits on major roads in my TomTom.

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            • #7
              Originally posted by Nova Artist View Post
              In terms of erratic readings, as the car does seem to go through more fuel when cold this expains some of the very high early values, and as the manual reading calculates from a smaller set of drive time, it will start to differ from the auto reading as the days wear on, which always shows the last 4 hours of actual drive time (except when reset).
              As the measurement is a function of consumption vs distance, it will always read higher when distance travelled is minimal and average out to a lower amount when the distance increases. When I left the station car park tonight I had to idle for a minute or two after starting to wait for a car to clear; when the consumption started reading within 500m it read 35l/100km; by the time I had travelled 2 km it had settled down to 10.5l/100km

              I've always considered the manual reading as being this crrent trip (or since I started the car) whereas the manual is the average since last time I set reset. As I reset the button 50 km after picking up the car, I consider the average showing on this to be a fair indication of average fuel consumption over 1500 km. (Not totally sure my impression is correct, but am I the only person who consider the manual is written in Japlish and need the assistance of a good technical writer?)

              Testing fuel consumption over one tank is not that accurate either, unless you fill up to the same level (say 1st cut off at the same fuel pump) at the same temperature under the same barometric pressure, you don't actually know the tank is full exactly the same amount each time. If you are going to do it this way you really need to average it out over a few tankfuls

              Garth

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              • #8
                Garth writes; I consider the average showing on this to be a fair indication of average fuel consumption over 1500 km.

                I wish the car did give average fuel consumption until resetting for the "manual" setting, but it appears the computer memory only holds 4 hours of data - and we have noticed this recently, after getting 9.4L/100km average for about 200 km on a flat country run, once I started going back to city driving the long term average started jumping up more rapidly than it should have once the really good average consumption graph lines with nice high lines (closer to 0) started disappearing off the edge of the line chart. Thus, we do not seem to have a system that will give us averages over an entire tank. I only state that I have data for 5700 km simply because I record all data into an excel spreadsheet purely so I can double check the fuel charges to my account against the lease statements that I get every 3 months. However, manually recording the data this way gives me some insight into fuel usage of the car. Even if I had not touched the manual reset button since new, the data on the screen would not be the average over the distance since new, only the last 4 hours of drive time. Thus, if I drove for 4 hours straight, the manual and auto readings would be exactly the same.
                Mar07 build NS LWB VRX Auto

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                • #9
                  Range (Fuel Remaining) Display

                  I find this even more misleading than the Fuel Economy display can be.

                  I refuelled when the gauge showed at 1/4 Full mark and it took 72 litres (20 litres remaining) after driving 540km since the last fill.

                  When I drove off, it showed I had 500km range ???????

                  I then drove in very light traffic and then on the freeway - so for the next 90 minutes the range kept on increasing, though obviously I was using fuel !

                  I know that predicting anything is flaky, but I really wonder what algorithm they use to predict range. They seem to use a very short averaging period for the fuel consumption to use for the range.
                  Mike R. Sydney. Pajero GLS NX Silver Jan15. DiD Auto. STILL grossly disappointed with the errors in Speed Limits on major roads in my TomTom.

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                  • #10
                    as your fuel economy improves so will your range

                    mike how big is your fuel tank?? 72l plus 20 remaining... have you got a long range fitted.
                    SWB NT X DiD its R E D

                    SWB NS X DiD that's double D's !! Retired

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