I am going to talk about this, because it relates to the piggy back vs tune.
The piggy back hides boost from the ECU, I think we all understand that now. What people don't understand is that the turbo compressor speeds tables are built into the ECU, and those speeds are calculated off of the boost levels being recorded by the ECU. So... if you are hiding boost from the ECU, it cannot calculate proper turbo speeds.
Turbo speeds fall into a lot of maps for different protection levels. A big one would be turbine temp safety limit. If you hide the boost, turbo speeds are not accurate, now we have turbine temps off as well. If you hide to much boost, then shift control for BOV/surge valve operation. All the calculations are off, and possible turbo damage can result from this type of hidden boost signal.
I have seen turbo failures from aggressive settings in the turbo speed maps on stock turbo cars. It was actually a problem for a little while in the Hyundai market with a Korean tuner cranking up the turbo speeds to max, and the turbos were running full speed with the surge valve wide open. This created a massive turbo speed attempting to reach target boost, and ended up with several cars with failing turbos.
Now, not all ECU's are programmed with calculated turbo speeds... it just so happens that the Stinger has these maps and these have to be monitored carefully to avoid turbo overspeed.
Hope this helps.
It's true that high turbine speed is normally what leads to turbo failure. What is high turbine speed is relative and generally caused by high boost targets at high engine speeds.
There isn't a turbine speed sensor on this platform, just like there isn't an exhaust gas temperature (EGT) sensor, they are both modeled values. Once you change the tuning their modeling changes. Once you add hard parts like intakes, exhaust changes, etc, their modeling changes. There are modeled limits that need to be kept under to avoid limp modes, and hard limits you'll want to stay under to avoid physical turbo damage.
How you technically handle it safely with flash tuning will be different than how you safely handle it with JB4 tuning.
On the flash side you'll adjust several tables to increase the modeled turbine speed limit, or adjust the modeled constants so the turbine speed modeling is lower than it would otherwise be. You need to ensure tables are set properly so the physical limits are not exceeded.
On the JB4 end the turbine speed will always be registered as stock values, so the JB4 only has to manage physical turbine speed by actively managing the boost target especially at higher RPM, based on engine criteria coming in via CANbus.
Remember turbine speed is a largely a function of WGDC, engine speed, air density, and EGT. It's going to take so much speed to hit a specific boost target at a specific engine speed and specific volumetric efficiency. So bottom line is the tuner has to provide boost profiles that are within the hardware's limits. People often ask why we let boost taper to ~12psi at redline on the JB4 maps for example. This is why.
Worth noting the modeled turbine speed is a loggable parameter. I have it setup to monitor in our test firmware, before I poked around and realized there was no sensor making it useless. If there is demand we can add it to the public firmware as maybe the flash tuner guys will find it useful. There are a few parameters we plan to get in there including WGDC.
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