Quote:
Originally Posted by arghx7
There's a lot of discussion here among different people and scenarios that I'm trying to unravel.
First question: is this a matter of the fuel trims moving around more than would be ideal or is there an actual driveability, knock, etc problem?
Second: Are we talking about stock port injectors, obviously stock DI injectors, and stock MAF scaling or scaling that has been judged ok before the PI and DI balance was changed?
I suspect there's a bunch of wall wetting compensation, gas flow model, or injector flow compensation that is poorly understood because we don't have actual block diagrams of how the software works, just whatever has been reverse engineered.
My position is, generally speaking and subject to case by case revision--if the fuel trims are just moving around more who cares? That's their job. They're compensating for some inscrutable fuel calculation that hasn't been unraveled, or more likely, production tolerances in injectors, given that the stock values were for some mean spec part most likely.
 Is there an actual problem with the car here or are we just trying to make the fuel trim lines on an excel graph look pretty |
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arghx7 @
solidONE @
steve99 @
Kodename47 @
ztan
My concern is if the fuel trims go up or down too much say more than 10% it will take the estimated load along with it. Estimated load = Originally assumed load through MAF signal +- corrections from fuel trim. This means the cam and spark lookup will move around unnecessarily?
I dont know how exactly it works on the FA20 so this is just my assumption. This is assuming that most OEMs trust their fuel modeling more than air flow modeling. So when fuel trim moves the load estimation moves as well.
My other concern is how is MAF scaling going to fix this? For example say if by going 100%PFI at low loads causes the LFTF there to go 10% +ve causing a load estimation to go up 10%. The MAF there would be moved up 10% at the same Voltage to bring the LTFT to 0% but we still have the same problem because now the MAF readings are higher (artificially) causing a higher load estimation and hence spark/cam lookup = bad combustion or knock depending on which direction we go in load lookup