"Fuel Used" Meter on DIC Accurate?

[Prestonia24]

Comment:
I've been resetting the fuel used meter on every fill up, and every time I get 'gas' (yes, diesel is not gas, but the term is synonymous with fuelling) I notice that if it says i've used 22.33 gallons, that it'll fill up to the same point with +/- 0.1 gallon... which i've got to say is pretty damn good and extremely useful (Props to GM). Especially when i'm trying to figure out how much gas I used when I was idling in bumper to bumper traffic, not getting above 15mph...

At some point in the future i'm considering an external fuel tank (In bed) and if I can't get a decent fuel guage setup, i'd still like to know how much fuel is being consumed (for mileage purposes).

Question(s):
1.) Does anyone know where the fuel meter registers from, whether it's on the engine side, or tank side...

2.) How does the DIC calculate the MPG listed? (I.E. by taking the reading from the 'fuel used' and dividing it by some arbitrary interval of miles...) This is important for if I added an external fuel tank, and still wanted the DIC's economy meter to function...

On an aside, my current hand calculated fuel economy is about 15.8, mixed streets and highway (1100 miles on the truck) (High of 18.5 driving all freeway at 75mph, Low of 13.8 - all streets :sad: )


Also haven't paid more than 3.05/gallon for Diesel in the last 2 months, low of 2.95/gallon... (shopping around is good... Especially in Los Angeles)

[More Power]

From what you're reporting, it sounds as though you haven't changed the tire size or are using any performance mods. Changing these variables will affect the accuracy of the DIC.

The vehicle ECM uses an algorithm to calculate average fuel consumption and mpg based on several fuel system and vehicle inputs. It's a best guess average based on extensive laboratory engine dyno tests performed by GM long before the first trucks of that model year are sold. Every vehicle is an individual, with some producing numbers pretty close to reality and others less so.

As long as you don't change the truck much, you could continue to use the DIC to track fuel consumption when adding an auxiliary fuel tank. The level sender in the fuel tank is not used in the ECM DIC calculations (IIRC).

Jim

[Prestonia24]

5 years and 46,000 miles later. I'm still getting about 17mpg tank averages (with Banks 6 gun (on level 4) for the last 40k miles or so)

on my last fill up a few days ago, filled it up with 22.79 gallons and the DIC said it burned 23.4, which is about 97% accurate.

Since I've owned the truck, It's always been about 95% accurate, erring on the side of safety (saying it has burned slightly more fuel than it truly has) which is just fine by me.

With the standard 26 gallon tank, the low fuel indicator light, almost always comes on between 21.5 gallons used and 22.0 gallons used, indicating there's a little more than 4 gallons left in the tank (enough to get me at least another 50 miles)

While the truck is now "out of warranty" I am glad to be the proud holder of the pink-slip (Thank you GMAC :D )

[Kennedy]

Comment:
I've been resetting the fuel used meter on every fill up, and every time I get 'gas' (yes, diesel is not gas, but the term is synonymous with fuelling) I notice that if it says i've used 22.33 gallons, that it'll fill up to the same point with +/- 0.1 gallon... which i've got to say is pretty damn good and extremely useful (Props to GM). Especially when i'm trying to figure out how much gas I used when I was idling in bumper to bumper traffic, not getting above 15mph...

At some point in the future i'm considering an external fuel tank (In bed) and if I can't get a decent fuel guage setup, i'd still like to know how much fuel is being consumed (for mileage purposes).

Question(s):
1.) Does anyone know where the fuel meter registers from, whether it's on the engine side, or tank side...There is no "meter" persay in the system. It's all calculations.

2.) How does the DIC calculate the MPG listed? (I.E. by taking the reading from the 'fuel used' and dividing it by some arbitrary interval of miles...) This is important for if I added an external fuel tank, and still wanted the DIC's economy meter to function... The ECM uses the formula for time-pressure-orifice (actually in a simpler form mm3) and uses this fueling rate to calculate the mpg based on number of firing events per mile. This can be quite accurate so long as the injectors remain in spec and the speedo (tire size) calibration is also correct.

On an aside, my current hand calculated fuel economy is about 15.8, mixed streets and highway (1100 miles on the truck) (High of 18.5 driving all freeway at 75mph, Low of 13.8 - all streets :sad: )


Also haven't paid more than 3.05/gallon for Diesel in the last 2 months, low of 2.95/gallon... (shopping around is good... Especially in Los Angeles)


I think I explained this correctly...

[moss6]

"The ECM uses the formula for time-pressure-orifice (actually in a simpler form mm3) and uses this fueling rate to calculate the mpg based on number of firing events per mile. This can be quite accurate so long as the injectors remain in spec and the speedo (tire size) calibration is also correct."

Or if you take your LML in for the DEF re-programming recall; then your fuel used will no longer be accurate, a bummer; I used to count on it.
Randy