I've been tuning in pure OL for quite a while now and I have gotten pretty comfortable with everything. I have the car running really good... but the pursuit of improvement continues.
One thing that drives me crazy is a anomaly in both my VE tables. My VE tables are inconsistent from 1,200 rpm - 2,400 rpms. VE table RPM break points 1,200, 1600 and 2,400 look as they should, while 1,400 and 2000 want lower values than the rpm breaks before them. In a nutshell.... the car fuels very well and AFR Err is typically <2%.
However, from a visual standpoint... my tables and have noticeable peaks and valleys in them from 1,200 - 2,400.
Part of me says... if it fuels right stop worrying about it.... but there has to be a reason for the variances.
I noticed that Fuel Trim Boundaries (under Oxygen Sensors) has the RPM boundaries set for 1,200, 1,600 and 2,400...... Now imagine that. However this section appears to be for Closed loop tuning.
I know GM uses Fuel Trim Boundaries to basically quadrant off the VE tables into 16 areas. We have (3) rpm breakpoints and (5) VE breakpoints.
Just to see.... I zeroed everything out for both VE and RPM in the Fuel Trim Boundaries, but it still seems that the tune wants lower VE values at 1,400 and 2,000.
Another kicker that is that VE responds appropriately (idle is perfect) below 1,200 rpms and above say 2,600 rpms. My VE peaks around 5,100 rpms and tapers off to 6,500 rpms.