WOW, Wish I would have....
...purchased the right truck the first time. First run today with new to us GMC 3500 and WOW. The difference between the GMC and F350 is night and day. Truck pulled our fiver over same hills that o...
Forum Discussion
transamz9 wrote:BurbMan wrote:jus2shy wrote:
The unison ring is what synchronizes all the guides/vanes on the turbine side of the wheel. These guides can close to add more velocity to the exhaust gases allowing the turbo to spool up sooner and higher. The vanes can also be opened to allow for more exhaust flow while maintaining optimum pressure. These rings can be cleaned, lots of youtube videos on how to take care of that. It is these guides/vanes that allow the turbo to be called a "Variable Geometry" turbo. Without this ability, you'd have to settle for either low-end grunt or high-end power. Variable Geometry gives a turbo far more operating range. Hope that makes sense.
Thank you, that makes sense. So if the EGR cooler goes, you get coolant in the intake which in turn causes the unison ring to rust, which in turn impedes its ability to vary the turbo geometry, which in turn limits the turbo's effectiveness over various RPM ranges, which in turn causes a general power loss? Do I have that right?
Yes which will then cause an "overboost" or "underboost" condition that so many people talk about. An overboost condition sends the motor into limp mode.
The 6.0L that I drove didn't go into limp mode per se. When the turbo would overboost it would blow the CAC hoses off. Sometimes so violently that you could see the hood lift. The mechanic at the Ford dealer told me he had seen them dent the hood from the bottom on extreme cases.
