Scanguage II Calibration: 'Adjustment Factor on Fillup'
 

As per the manual:

"The screen will show how much fuel the ScanGauge has computed to have been used since the last time a FILLUP was done. Use the value displayed by the pump or on the receipt to adjust this value up or down (using the upper buttons) to match it as close as possible. The lower line shows the ?adjustment factor? in percent that the ScanGauge will use to compute fuel use. Press DONE after you have finished adjusting the indicated fuel to match the actual pumped fuel. Pressing DONE enters this correction factor into flash memory"


I'm thinking that the adjustment factor on the fillup is something I will ignore from here on...

When I first got the unit, I did a fill, and then told the Scanguage I had done a fill, but did not put in the real amount.

I then drove for a day, and did another fill - adjusting the fillup in Scanguage to match what I had actually used. The 'adjustment factor' was 19.4%

My next tank was 4.0 L/100 (7.7 litres / 192 kms), but Scanguage showed 4.7

If that 19.4% had actually shown zero, I'm thinking the fuel economy in Scanguage for this tank would have matched... ? Am I correct?

I have verified and adjusted the Scanguage speed against a GPS, and verified the distance travelled on a longer trip, and I am within 2/10 of 1%... (I wish you could enter more than just whole numbers for this adjustment - I could make it exact...)

Is this likely to be the only calibration required? It seems the fillup amount 'adjustment factor' introduces too many variables... did you use the same pump, facing the same way, filled to the exact same level... and add to that exaggerated differences on partial fills...

How have others done it? Any examples of how the fillup 'adjustment factor' has helped? Have you averaged out 10 fills FE at the same pump against the Scanguage FE for the same?

I have the SGI and mine was consitantly within .1 gallons on every fill after the first adjustment. I only had to adjust mine 1%. Check to be sure you have the engine parameters set for your engine size on the setup menu and that it is set for diesel fuel.

I don't know how far you drive in a day, but I'm guessing it wasn't far enough to use enough fuel to reduce the significance of the variation from fill to fill. The ScanGauge manual recommends using at least 10 gallons or 3/4 of a tank (something like that) before attempting this procedure. Best practice would be to fill the tank, reset the ScanGauge with 0% correction factor, and drive through a whole tank before trying to match the ScanGauge reading to the next pump reading. Go through that once or twice and you should be in good shape as long as the rest of the parameters are set correctly. Just keep in mind that it's not a perfect science, and the ScanGauge may be a little over or under depending on how much gas the pump feels like giving you on a particular day.

Yeah and don't forget to allow for pumping error - if you pump slow it puts more gas in than it says it pumps and you will fill up with less gallons and show higher gas mileage.

Have you tested this theory rigorously?

I only fill up every three weeks or so - trip to Maine this weekend so that should be good for two tanks of fuel - will check it more then.

Cool. How are you going to test it?

Precisely - that is to be expected.

I do have 'Diesela' and .8 litre engine size selected.

After that, it seems to me there are primarily two calibrations that effect the FE number - the speed - and the fillup 'adjustment factor'.

Being that I have calibrated the speed with a GPS, I'm leaning towards ignoring the fillup 'adjustment factor', unless after 5000 miles, there is a percentage point or two difference between the cumulative S II FE, and the FE number obtained through the total volume of fuel purchased, and total (GPS calibrated) distance travelled.

Perhaps that is where I will start - simply start keeping track of the Scanguage 'tank' data along side my existing data, and then compare it every 1000 miles to ensure it is within 1% overall. Obviously some folks really trust the numbers from the Scanguage - and I'm merely trying to get to that level objectively.

There is one advantage I have - in that I can fill right to the top of the filler tube in my smart - visually seeing the level of the fuel... and I can ensure there is no foam... this has allowed me to calculate very accurate tank by tank FE numbers, even on partial fills, simply based on GPS distance and fuel volume filled... BUT - it would be so much better to have a second source for a FE number, hence Scanguage.

i already filled and waiting to refill to check the accuracy too. sg has been showing my trips to work arounf 36-38 mpg but when i checked mileage was only 32.7. my wqay to compute mileage was that when low fuel light came on i put $20 in and next time light camer on i ised the number of gallons and miles drive3d to figure mileage. e-mailed ron at linear logics and he told me that i needed to do the corect fill and refill for best accuracy.

Yes, enquiring minds would like to know. I have wondered the same thing...

Here's how I fill my diesel smart normally:

First, I fill at full pump speed until I can hear the fuel starting to come up to the bottom of the filler neck... this is typically when the auto shut off would happen.

Secondly, I typically STOP at this point, and let the 'foam' settle for 10-15 seconds, which probably also allows for more air to escape, and creates more room for fuel.

Thirdly, I fill at a slower rate until the fuel level is right at the top of the filler tube... making sure there is no foam.

Anyway - all of this WAS in an effort to try and be consistent with fills - so I could use the data to show FE of specific 'runs', 'tanks', and the associated gains/losses of tire PSI, tire sizes etc...

At the end of the day, and hence my initial query, I'm looking to use Scanguage to narrow live performance down further... I have a host of possible changes I could make to the car, and I do want to know the effect of each.