Before I get into this thread let me first start by saying it is nice to have friends. There are may reasons why a turbo will surge and for a vgt turbo there is even more reasons. If the ECM(PMC) is opening or closing vanes at wrong time surge, if the unison ring is stuck surge, if fuel is coming in at wrong time surge, VGT actuator not working or weak surge. There are many more reasons but for a VGT turbo to surge, tuning surge, the list is many and hard to pin down. One thing I can say is that if there are so many turbos out there and I'm talking about the MTW ones now and only but 3-5 are surging and the others about 80-90 now are not surging then it is the truck. What is it? don't know without going through the truck certain trucks to find out.
I have just found out about a truck that has been out there runing and having problems with surging for a long time, I sent out a hybrid to replace the stage 1(actually oringal durastroke) and the truck still surged, even sent out a stock housing and wheel so they could switch back if the couldn't getthe surging problem to go away. Well in this situtation, it was the truck, the owner and friend contacted a friend of mine and told him that the turbo was surging and even after they tried all sorts of tunes and switching the housing they still had the problem. Must be the turbo, well my friend told them to check all the senors to make sure that they where all clean. EBP, lines and ports, next the map sensor and ports. They found the map sensor port in the intake clogged a little, and then they tried to blow through the line (hose) that goes to the map sensor and it was also clogged, you could blow through it just not freely. They cleaned out the map sensor and all the lines, EBP lines brake fuild, the port going in intake with a wire to make sure the opening was clear. So guess what no surge, that right the ECM was not getting the right readings from the sensors and was keeping vanes closed to much and not opening when the surge was about to happen. Van timing with the ECM not getting correct readings. Not saying that this is the case with all the trucks that have the surging issues, like I stated before, it could be alot of things, just that one should go through and check all the sensors and ports to make sure everthing is correct. A stock turbo could run and not surge, but anytime you go with high performance it will find something if it's not right.
I started this thread to help and to better understand why turbos surge and will continue to update with more data and examples of things found. Everone can miss something so it's not a thread at pointing figures or blaming, just a thread of infomation to learn from. If anyone has another this that fixed a problem stated on here. Hell I had one member that couldn't load a tune on his computer and replacd it samething wouldn't load. Found a short on the oil pressure switch and fixed the problem, what's the oil pressure switch do with the ECM not taking a tune? well if I had to guess since I don't have the wiring schematic in front of me, I would have to say that the ecm not seeing the oil pressure was causing it to go into default mode, no check engine light or anything else just staied in default. Crazy, Crazy, just one more example of the ecm in these trucks. Thanks to all.