No vacuum on the turbo actuator - full boost or no boost?

So after reading for over an hour, I am confused.

The limp mode thread says that the actuator should start to move at 3-4Hg and bottom out at 18Hg. But it also says that a vacuum leak can cause overboost.

I have overboost. The turbo appears to be stuck in full boost. The ECU is limiting fuel to keep it under control.

What is the relaxed, no vacuum state of the turbo actuator? Full boost or no boost?

lol, and here is everybody saying it is every which way.

Vanes closed = boost, no no, vanes open = boost
Vacuum on actuator closes vanes, no its the other way



http://forums.tdiclub.com/showthread.php?t=300468&highlight=overboost

Does your actuator move all the way through it's range?

no vacuum = no boost if everything is working correctly...

It looks like I have two problems. My actuator is rusted into two pieces so the bottom is just hanging off the turbo and flopping up and down as vacuum is applied/relieved.

My turbo also does not have the full range of movement. It is in the full turbo position and it is sticking well before getting to the no turbo position.

I have a feeling I have been living with a marginally overboosted car for the last 5 years and didn't know it. I will be interested to see how much power it delivers when all this is sorted out.

The thing that caught me off guard is I did not realize that the turbo is in full application by default from idle. N75 is delivering full vacuum at idle. So that means that the ECU backs off the turbo as the engine revs then?

I thought it was the other way around all this time.