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.
This tune had a couple of fixes to try to eliminate the torque management advance. They were partially successful.
Previous run showed two spikes with up to 12 degrees of torque management advance; this run had one spike with only 4.2 degrees. Although there is still some TMA, this was progress.
I have been showing the graphs as xy graphs, hp to rpm for example, which is the way a dyno might show similar data. However, this does not consider the time aspect — it takes much less time for the engine to get to 4500 rpm than from 4500 to 6500 for example.
This shows time offset from hptuners scan along the X axis instead of RPM. My impression is that they are time in seconds of the scan. It is time correct, and RPM builds from left to right but I have not discerned a best way to show both the HP vs RPM and HP vs TIME on one chart yet.
This second chart is useful however for understanding when events occur in time — go WOT, tip-in and boost, torque, and RPM build rapidly. A largely flat torque curve that matches the boost curve.
The remaining TMA retard appears to coincide with rapid boost development. My next test will be to see if that is a limiter.