how a vgt turbo works when mechanicaly controled
 

we will use a 351VGT holste turbo for our example but all knowledge on any vgt turbo is great. i want to kow how do you mechanicaly run a vgt turbo? if you use a mechanicaly controled how do you have the vgt i feel like it would be a fixed blad and then the waist gate would let it out at a set psi. let me know thanks pictures are great!

If its a fixed blade then its not a VGT turbo, I dont know how you can run them mechanically, all the ones I know run of the PCM

Using a wastegate will choke the engine at part throttle loads. You must use a system that limits boost pressure based on engine load or throttle position.

Like this: http://mercedesforum.com/forum/diese...ne-load-49672/

Is it possible to calculated engine load based on revs versus throttle position ?

I've seen a setup on a awd talon with a 6.0 psd trubo where it was connected to the throttle with a cable and spring, which would pull it closed when you pushed the throttle down and a wastegate actuator to push it back open when it built boost and overcame the throttle spring. Who said ricers arent good for anything :p

HMMM intereasting, learning stuff every day...

If I had paint on my phone id draw it up, was at a car show a couple years back.

Thats no different and just as bad a putting a wastegate straight on the control arm. G@ssers have no comparison to diesels when talking about turbos, especially VNT/VGT turbos. A g@sser has very little airflow at part throttle because they are choked off, a diesel is always flowing lots of air even at idle.
With his system you're not controlling boost pressure, you're controlling how fast the turbo spools up to maximum pressure.

There isn't a good way to control a VGT turbo mechanically. You either end up with several "stages" of boost like my controller or you end up with little better than a traditional wastegate. You really need electronics and a programmable map.

Very good expressed.
In the Jeep Liberty the VGT is controlled by boost pressure. By adjusting the VGT vane angle is is possible to control the airflow to the turbine wheel.
In this way it is possible to have an optimized turbo spool up.

But:
Electronics are only used to adjust the airflow (and therefore the vane angle) to the turbine wheel. Even VGT turbos can still have an old style wastegate to control overboost conditions.

I may have missed them completely but I have not seen wastegates on VNT equiped TDIs and people mention that they control boost just by the vane angle.

From a map I've seen for a DIY VNT controller, there is a target boost based on rpm and throttle position.