Originally Posted by synolimit
this kinda contradicts its self. your saying the MAF can make the corrections and thats it! but then you say the tuner needs to adjust scaling. so ill hold what i said first. the MAF can adjust BUT not much! thats why you cant throw in 1000cc injectors and be ok. why you cant add a CAI, DP, header, UP CBE and be ok. i put on a CAI with no adjustment and shot up to 33MPG. the car was WAY to lean. the AFR and scaling still needs adjusted because the MAF CANT do it all.
There are no contradictions there, but you have much to learn about how MAF-based fueling works.
You seem to be thinking that the MAF sensor's job is to correct for changes in AFR, but that is not the case. The MAF sensor, in conjuction with MAF sensor scaling, tells the ECU how much air the engine is flowing. Period.
The ECU uses that air flow rate, plus its knowledge of the injector characteristics (flow rate and latency) to open the injectors just long enough to inject the appropriate amount of fuel to get the desired AFR.
If the engine starts flowing more air, and the MAF scaling is correct, the ECU still knows how much air the engine is flow, so it can still inject the correct amount of fuel to achieve the desired AFR.
Make sense now?