Discussion and questions related to the course Reflashing
Hi, apologies in advance if this is a dumb question, but im just looking for some clarification.
As I understand it, tuning with a MAF based system you have the MAF scaling table and the target lambda table, and the short term fuel trims. When scaling the MAF youre looking at the percentage needed to change the MAF calibration, and how far off the MAF calibration is by using the feedback. So when its calibrated, it uses the load and just calculates the required PW for the desired lambda and if you want a richer lambda you just change the target? Also When scaling the MAF vs Scaling the Injectors you look at both the Short term fuel trims as well as the measured vs commanded lambda for both scaling procedures?
Also I understand that with MAP based systems the airflow is calculated and includes a VE table. The fuel parameters are input into the ECU as well as the target lambda, and the VE table should be modified if the target and measured lambda are different to represent a true VE table.
Hey John, yes you've pretty much got it all spot on. the MAF measures airflow and then inside the ECM are tables defining injector flow. With this information the ECM can calculate what injector pulse width to provide in order to achieve the target AFR. The STFT and LTFT are there to make any small adjustments necessary to account for any variations we may see and if all is tuned correctly the trims should be very close to zero. If you want to change the AFR you simply change the target table.
With a MAP based system the mass airflow is calculated using the ideal gas law. Provided the injector data is correct then you ned to change the VE table until your measured AFR matches your target.
Thank you so much!