Today’s scan showed torque management advance on both runs despite the changes in the tune to try to address it. I also have some misfires on cylinder 3, and the Manifold air temperature is not steadily dropping during WOT.

The misfires mean it is time to change the sparkplugs, regapping to a smaller gap due to the increased boost. The ATS-V LF4 is quite busy on top, so I will need to remove several things to get to the on-plug coil packs and plugs, but hopefully I can get that done soon.

The MAT trend means the charge cooler wants to be bled/vented again. I did that this morning, but will revisit a couple of times to try to ensure all the air in the system is replaced by new Dexcool coolant. I am surprised it needed doing again so soon, but I suspect in the heat the system expands and gulps in air now and then.

The continued TMA means that the changes in the tune for today were not successful, and back to the drawing board to try to sort out why I am getting TMA there, or simply table it for now. As I like to say, it bears more study. I plan to revert to the prior tune since today’s changes were not successful in addressing the TMA.

For today’s test I increased the pressure delta. One test (pictured) had no TMA at all (yay)

Boost comes right up, and torque is pretty flat. Cooler day, so almost SAE1349 conditions with a small correction factor of 0.2%.

The other test sample for today does show some TMA.

The rate of increase may be addressed now, but I note that the new TMA happens when Cylinder airmass exceeds 1.32. More study is needed; that is below the current tune knock airmass table. I suspect this is a 3rd source of TMA however.

This chart compares total cylinder airmass with boost and TMA

I have made progress in reducing the torque management advance (TMA) by RPM Limit Accel Thresh vs. Accel. However, there is still some TMA remaining. I suspect there were multiple sources for the TMA — we solved one. My next hypothesis is that there is some torque management advance coming from boost rate of increase exceeding the allowed pressure delta.

I see in the prior graphs that when there is torque management advance there is also rapid boost increase. I assumed that this was due to the TMA, but it got me wondering if the rapid boost increase was actually a causal factor for the TMA.

I am not clear how Cadillac calculates rate of boost increase. To try to model the rate, in the graph above I first graphed the limit in blue. Then I considered a rate of increase per 0.1 seconds from my log 1E. In other words, what was the % of increase in boost over 0.1 seconds? I graphed that in red. Finally, where do we see TMA on the same run? I graphed that in gray. I can see that the TMA correlates with the boost increase rate. Correlation does not equate to causation, but it is a clue.

My next test will be to increase the Pressure Delta Factor to determine if that has an impact on torque management advance.