How do Ecoboost PCM's handle altitude?
I have a 2014 F150 Ecoboost and am curious how the PCM adjusts boost and airflow based on altitude(ambient pressure). I have spent a bit of time in the tune and have found nothing that appears to be any kind of adjustment.
Do they simply use the overspeed table(45559) under Engine->Airflow->Turbocharger?
The reason I ask is because I live at 6500' and I have multiple tunes from different tuners that seem to respond in different ways. My stock tune only seems to like to flow ~30-32 lbs/min at this elevation while most of my tow/performance tunes will hit in the 36-37 lbs/min range at around 50% WGDC. Then I have this one tune that tries to blow up my turbos. It will hit 38-39 lbs/min @ ~4500rpm and then it sends the WGDC to 100% as the RPM's keep rising. Luckily the wastegates must be blowing open and it appears that my turbos don't exceed the 220,000 rpm threshhold.
Anyways, just curious why some tunes would be ok and others not. What parameter would they change to result in the PCM trying to go beyond the maximum flow of the turbo at this altitude?