One other thing I was thinking of today is with respect to volume correction factors - in Canada, fuel gets sold at the retail level at the equivalent volume based on a temperature of 15 C. The colder the temperature, the more dense the fuel becomes and the larger the equivalent volume.

For example, 100 litres of fuel at 15 C has a volume correction factor of 1.000. However, 100 litres of fuel at -15 C has a volume correction factor applied of 1.0251 or 2.51%. So you if pump 100 actual litres into your tank at -15 C the actual volume showing on the pump will be 102.51. This factor is applied to account for expansion and contraction of fuel at differing temperatures.

Above 15 C and the correction factor goes the other way.

In any case, I doubt that VCF's would get accounted for in the algorithm so this may be part of the issue.

 

I KNEW you guys were going to run into problems when you went metric! I understand the logic and for fuels like propane where it is dispensed from a truck exposed to the elements, it makes sense to adjust to a standardized temperature. But why fuel held in an underground tank that is pretty much stabilized at a set temperature?

Have you considered the other possibility in the equation? That your kilometers may be off? I don't know enough about Ford's speedometer/odometer set up. Could there be an error in the actual kilometers it is reporting?

 

I blame it on the Queen...

 

Personally I think it is all Prince Chuck's fault.

 

Well, I have also noticed a similar margin of error as rdenis, anywhere from 13% to 20%. There is no consistency that I can see in the margin of error. I will try to run in US units for a tank or two to see if the error is consistent or if it goes away.

On second thought, I don't think this will make a difference as when the display is switched to US units all of the numbers convert exactly... litres/gallons used, distance travelled, etc., so I am not sure there is anything we can do about this issue, other than wait for an explanation from Paul and the engineers at Ford.

 

I've posted in other threads that I believe the error in the gallons used is because the truck is not "counting" fuel used for "cleaning exhaust".

In my case the average error on fills which are 25 gallons or more is 1.85 gallons or 6.84%.

Knowing this, what I do now is just add 2 gallon to whatever the truck says and when the truck says 32 gal used, its time to fill up because really it is 34 gal used.

I never even look at the fuel gauge, only used the gallons used indicator. When I get the big tank I'll probably have to add 3 or 4 if my theory is correct.

I've experimented with this. You can try it yourself. After a cleaning exhaust thing is done, go fill up and then fill up again before the next cleaning exhaust happens. See what you see.

Anyway, that's what I think and I haven't heard an explanation that convinces me otherwise so I'm sticking to this for now.

 

I have been tracking fuel for 21500 miles now. My fuel computer were always within 2% of my actual fill up. These fills have been over 40 gallons since October when I installed the Titan tank. I have seen an error margin increase in the last 6 weeks or do but I do idle the truck a lot more. It also warms up 10 minutes a day because I remote start it. I hate the cold...

Regards

 

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Alex, I think you are correct that the truck is not "counting" fuel used for "cleaning exhaust". My last fill up I noticed the pump said I took 22.84 gals to fill my tank but my dash said the truck had burned 20.6 gals.. I have noticed this differance for some time in the fuel readings, but was unable to put my finger on the answer why till you mentioned it in your post..
Thanks Alex Good Thinking!

DJC

 

WOW, IF this is the cause for the discrepancy that's a lot of fuel to burn just to save the environment!

 

I kinda agree. I find it hard to accept that 2 gallons of fuel are used during an active regen cycle. I know it's possible, I don't dispute it, but wow. That's a lot of fuel in 10 minutes. I can drag a really big trailer for 10 miles on 1 gallon going 75mph.

 

I used to watch my regen times and mileage every time I would catch the fleeting announcement. I have timed the event by switching to the instant mileage screen for the fuel computer. I learned that the fuel mileage will start to drop almost immediately and continue to fall until it loses 3 to 4 mpg. After about 10 minutes, the fuel mileage begins it's climb back up. This would indicate the completion of the DPF event. Since I average 18 mpg or so this means for about 10 minutes I am losing around 20% of my fuel economy. Because my regenerations occur at intervals between 200 and 800 miles, actual impact is difficult to calculate but it is not anywhere near 2 gallons per DPF event. City driving results in more frequent DPF events. If that is the case, the 200 mile events would be 8 hours of driving time with a 25 mph average. The event takes 10 minutes out of 480 minutes of fuel consumption. This calculates to 2% . If I did the math correctly, this calculates to .22 additional gallons consumed in 200 miles. Not much. To the engineers out there, feel free to check my math.

I quit worrying about the DPF events 17000 miles ago.

I also quit hand calculating fuel mileage because during the time of the year when I do not warm up my truck, my hand calcs were never off more than 2% from the fuel computer readout. Most of the time it was within 1%. YMMV

Regards

 

Sorry for the delay, but I finally received a response regarding what fuel variable is being used for distance calculations.

Per Denso, the cluster supplier's resident engineer, the fuel calculations are based off of "Liters". Thinking about that for a minute, this does solve the issue of having different liquid measurements around the globe as everything is converted.

-Paul

 

I'm seeing roughly a 3% difference between computer and actual usage. Trucks in Vancouver.

 

Hey Paul - thanks for touching base again - not sure if Denso actually understands the issue I am having but given they are using litres as their standard, I wonder if they apply some kind of correction factor when converting to gallons. Regardless I wonder if they actually do any calibration of the "fuel consumption" or what their error tolerances are. Something is still seriously out of whack here - it would be handy to know what the algorithm is they use to calculate the fuel burn volume.

 

Thanks for the info Paul. This would mean that the Canadian trucks should be the most accurate in the calculations.

Now Chep's results are more in line with the US trucks unlike mine and rdenis' truck that vary wildly.

Is there any confirmation that we can get that would indicate whether or not the fuel used during DPF cleaning is registered? Or perhaps a rough idea as to how much fuel is used on an average filter clean cycle?