cro142 Member 25 Member For: 20y 11m 17d Location: Brisbane Posted 28/03/06 05:43 AM Share Posted 28/03/06 05:43 AM The trip computer on my BAII Turbo ute seems to give a wildly incorrect readout of average fuel consumption. I had suspected this for a while, and last week did a test which confirmed it.Over a full tank of fuel (~70 litres), and with the AVG L/100 zeroed at the fill, the trip computer read an average of 16.5 L/100km.However, using the old manual method of calculating the consumption from litres used and km travelled (neck to neck fill at start & finish), I calculated a consumption of 13.3 L/100km.Having used this manual method for calculating fuel consumption for many years prior to trip computers, I am satisfied that I can do this accurately.So, why the huge difference?? - 16.5 by the trip computer, and 13.3 by calculation!!Any ideas ?? Link to comment Share on other sites More sharing options...
Iconic Bionic My engine bay is Bionic Donating Members 3,726 Member For: 18y 7m 4d Gender: Male Location: Freeways Posted 28/03/06 05:52 AM Share Posted 28/03/06 05:52 AM Gremlins.well mine has only travelled 74K's (not 74,000) so I'll be keeping an eye on it. Link to comment Share on other sites More sharing options...
stang Donating Members 1,353 Member For: 20y 9m 3d Location: Melbourne Posted 28/03/06 05:55 AM Share Posted 28/03/06 05:55 AM Gremlins.well mine has only travelled 74K's (not 74,000) so I'll be keeping an eye on it.There is no accuracy treat as a guide only. Link to comment Share on other sites More sharing options...
Cashie Donating Members 663 Member For: 21y 8m 26d Gender: Male Location: Perth Posted 28/03/06 06:15 AM Share Posted 28/03/06 06:15 AM In all three of my BAs it has always read about 1l/100kms higher than when I manually work it out.. Link to comment Share on other sites More sharing options...
bad inferno Member 130 Member For: 19y 2m 8d Posted 28/03/06 09:42 AM Share Posted 28/03/06 09:42 AM don't really know however have come to this conclusion:In the old days they could just measure the flow into the carbie with a simple flow meter, very accurate. However now with fuel injection and a pressurised header and return line you cannot measure the fuel supply anymore. I think they just use an estimate based upon injector frequency.rob Link to comment Share on other sites More sharing options...
BlueXR6Turbo The Best Member Donating Members 1,970 Member For: 21y 9m 14d Gender: Male Location: Adelaide Posted 28/03/06 01:34 PM Share Posted 28/03/06 01:34 PM Not long after I first got my car I compared the trip computer with manually calculated fuel economy, and it worked out to about 2L/100km difference. So it seems like they're all out a bit. I think the trip computer is really only any good to compare your fuel economy with how it has been historically, e.g. if it's getting better/worse. Link to comment Share on other sites More sharing options...
cro142 Member 25 Member For: 20y 11m 17d Location: Brisbane Posted 28/03/06 11:51 PM Author Share Posted 28/03/06 11:51 PM Yeah, it seems these readouts are consistently off.I have had 3 other BA's and the readout was off by about 1L/100km - but this one is off the planet with a difference of around 3L/100km.Sure makes for a depressing read before you know not to believe it!! Link to comment Share on other sites More sharing options...
Paradoxx Colossal Member Member 5,049 Member For: 20y 1m 29d Gender: Male Location: Perth, WA Posted 29/03/06 12:15 AM Share Posted 29/03/06 12:15 AM They aren't the most accurate way of measuring how much fuel you use, nor is your actual fuel gauge accurate enough to swear by. Even the speedo has a few km/h difference in EVERY falcon. All these little discrepencies will lead to a larger error with averages. Also if you have a look at the trip computer vs your odometer, you will notice the 0.1 will stay on the trip but the odometer will start from 0.0 every time you turn on the car. So effectively you could travel 0.9km and turn off the car and the odometer will reset to .0 again, and to tick it over you would have to drive a whole km for it to do so.I think I just confused myself. Link to comment Share on other sites More sharing options...
XtRmn8 570Nm @1800rpm Donating Members 2,441 Member For: 21y 1m 1d Gender: Male Location: Perth, WA Posted 29/03/06 02:03 AM Share Posted 29/03/06 02:03 AM My trip computer is not 100% accurate on consumption nor the DTE. For example my average consumption per 100km is about 0.5l more then what it is when I work it out manually. Also the DTE is not very accurate at all because the tank in a sedan is 68l and I have had the DTE down to 20km and I could only fill 60l max and that is will fuel spiling over the floor! Link to comment Share on other sites More sharing options...
gogo Member of team Kittens Member 609 Member For: 20y 8m Location: Melbourne Posted 29/03/06 02:04 AM Share Posted 29/03/06 02:04 AM My understanding is that the trip computer works off injector duty cycle to calculate fuel usage. This is why it is off the planet if you have bigger injectors and a piggy back ECU.I have typically found mine is out by approx 5% (higher fuel consumption on computer than actual fuel consumption) over obout 80,000kms.Really not too bad an indication. 3L/100km seems very large error. Average this out over 5 - 10 tankfuls and see if the error stays as large...cheers,Ben. Link to comment Share on other sites More sharing options...
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