I've been working on the tune of my LS7 (MSD intake, ported heads, cam w 116 lobe sep). The WOT fuel and spark was already done by the in-house calibrator at the facility which built the motor. I've been working on idle quality. In the process of that, I've developed this freakin' burning question...
Why does the rpm low side of the proportional idle table seem back-asswards?
I've read the long (and really good) thread here on idle tuning on this forum I've even been on the HPTuners forum and read another great thread on the subject. In both these threads reference is made by various members of those forums to the rpm low side of the proportional idle table having negative values. When rpm is below desired, these tables command the OS to add a negative airflow amount, ie: when rpm goes low, it's subtracting airflow, rather than adding which seems more intuitive.
This is not just some GM error with LS7 cals for E38s. I have found this characteristic in all sorts of GM calibrations for gasoline engines in vehicle platforms going back as far as 1999. That tells me there is a reason for GM's calibrators doing that.
Anyone know WTF is up with GM calibrating proportional idle like that?