Hi guys, I have spent countless hours trying to nail down a good, concrete method for tuning gen4 vehicles. Today I finally came up with a consistent method to dial in base airflow that I haven't seen posted before, so I wanted to share it with the community. This guide is for airflow and the adaptives only, so I am going to assume fueling is already dialed in if you decide to try my methods.
Before I dive into the steps, I want to briefly go over how the idle works on the gen4 pcm. There are 5 main areas that control idle: Airflow final minimum, base idle spark, spark over/under speed, proportional airflow, and integral airflow. These tables work closely together to attempt to keep your idle error to a minimum. Airflow final minimum is just your base air before any corrections. Base idle spark is self explanatory, as is over/under spark. Proportional airflow is an instant airflow correction based on real time rpm error. Integral is an offset airflow correction that gets applied to your airflow final minimum based on error over time. Proportional is to STFT as integral is to LTFT. It is your run of the mill PI controller, except it has different factors depending on how severe the RPM error is (the higher error, the more correction, and vice versa).
The problem is, the adaptives are way over tuned from the factory, so as soon as you put an aftermarket cam in that oscillates significantly more than the factory cam, you end up with a very over reactive idle. You get spark going one direction, over correcting, then airflow correcting back the other direction since it is a much slower correction than spark. It is a vicious cycle as spark correction competes directly against airflow correction.
The problem with just setting base airflow and calling it a day is you are tuning against two moving targets, the airflow correction and the spark correction. It's akin to trying to tune your maf table while the ve table is still enabled.
What you really want to be do is turn off the adaptives completely, lock in your spark, and find your optimal base running airflow. Base running airflow is nothing more than base TPS %. So how do we do this?