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Does anyone know how the VNT(variable turbo linkage) system works ?

Is this corect ? With engine off, VNT mechanical linkage rod is at it's longest and , in my opinion passes the pushdown test for free ( approx. 1") and easy movement. With engine at idle, linkage goes to it's shortest state.....then when I bring revs up to 2/3k ( stationary) I see the link rod extending.

I had a feeling it was the other way round ( i.e low vacuum at idle letting the rod go long) however, I'd be pleased to be put right here.

Thanks

Eddie
 

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post answered here too for the searchers and lurkers

The VNT actuator works off vacuum. This is the opposite of wastegate acuators which work off pressure. At rest there is no vacuum so the spring inside the can is the only force acting on it. Your understanding of it is correct. When it's at rest the vanes are wide open and the rod is longest, when the actuator gets full vacuum the vanes are closed and the rod is shortest. When it's running it's somewhere in between. The car modulates vacuum using the N75 solenoid.

http://www.myturbodiesel.com/1000q/a4/VNT-wastegate-adjust.htm see here for some videos
 
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