Originally posted by lkinley:
No, Sandman... in open loop the PCM still looks at the MAF readings.
-Lance
Right, but the computer still doesn't know if the engine is running lean. It uses the MAF reading and a pre-programmed table to determine how much fuel the engine needs. I would think that opening the secondaries at relatively low rpm's would significantly affect how much air is getting into each cylinder, provided the TB is not causing too much of a restriction.
In other words, at cold engine, open loop operation, normal driving should be OK as the TB is the restriction. Open the TB up all the way (WOT) at cold engine, open loop, low RPM's, and you may lean it out enough to do damage...
I understand that the computer can adapt, and that the MAF system works MUCH better at this than the old speed density (like on my 88 Mustang GT). However, if you get too far out of spec, the fuel tables need to be reprogrammed, kind of like the supercharged engines and how they need a custom chip burned. You could do more mods with the Mustang engines because they were bigger displacement, and the percentage of total airflow change was smaller than that for our relatively low displacement engine.
