vroom_vroom

iTrader: (5)

odd question for you, does the gas milage estimator in the dash display on the gxp run off of fixed permitters from the factory or dose it continuously re learn. just curious if it loses accuracy if you disable dod or continue to mod your car

06MonteSS

it will change and be off until after mileage is put on...

i.e. if you flash your ecm with a tune, the mileage on the DIC will not be correct, because the learned fueling/fuel trims are reset and have to be relearned by the ecm and settle in...

any time you flash the ecm or change the engine/exhaust airflow characteristics of the car, the fueling will need to be relearned and settle in... which is usually done within 100 miles or so...

then the DIC value will be able to correctly calculate mileage...

nmp0098

Fuel trims have nothing to do with it. The DIC would be 100% accurate if your fuel injectors are built completely to spec. They can vary up to +/- 6% from the design specs, which is why high end builds use flow matched injectors (I believe that Cartuning gives you flow matched injectors with their kit). The ECM calculates how much fuel to inject based on the result of the air mass calculations (the resulting airmass is also used to calculate cylinder load, and therefore effects spark timing as well). It then takes that airmass, and using the value of stoich and any enrichment sources (like PE, or power enrichment) it calculates how much fuel mass to inject. There is an IFR table and a series of offsets stored in lookup tables that are used to calculate injector pulse width. If those look up tables are wrong, and they always are slightly wrong because we don't live in a perfect world, then the DIC will be off. The fuel trims are used to account for all of the variation that stacks up in the system. That includes the injectors, the airmass calculations, and fuel (ethanol content, energy content, incomplete fuel atomization when the intake valve is cold, etc.). The trims add or subtract fuel, but that amount is accounted for by the DIC. In other words, the final fuel amount, including any trimming, is used. If the trims are off, then combustion is off, but the DIC is fine.

The DIC is as accurate as your injectors are.

xxtheshockerxx

didnt know that. thanks for the info