AH64ID wrote:
Your observations on the ECM/PCM fuel curve are odd, mainly because that generation of diesel does not have any method of monitoring airflow. No mass airflow sensor means no fuel calibration based on airflow changes. The engine honestly doesn't "know" you changed anything.
Not entirely true.
7.3L's don't have a MAF sensor, but do have a MAP sensor, plumbed directly after the boost outlet into the intake manifold, the actual sensor is mounted near the heater fan, and it specifically measures boost the turbo is producing and so as to add the correct amount of fuel.
In a nutshell - A MAP sensor measures pressure in the manifold, and the MAF sensor measures flow.
A very common mod that needs to be done after someone chips a 7.3L is to put a low-pressure regulator on that very line going to the MAP sensor to limit what it sees to 20-21lbs boost, at 22lbs, it kicks the "Check Engine Light" with an overboost code.
I never did it because I prefer to just deal with the code vs run the mix lean by fooling the sensor. Mine is programmed not to do the dreaded "de-fuel on boost fault" which is also very common.
