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I'm not gonna explain the whole disassembly and function of the VNT turbo, becuse there is a whole lot of info out there.
This is just about adjusting the actuator stop screw in case you want to replace your CHRA.


Just a few hints though:
>Bolts that hold the turbo and bolts on the turbo itself are going to be a ***** to get off, so be prepared. I don't know if stuff like WD40's gonna help....
>Gonna need "cheating bars" and levers and some hammering.
>Take a picture of the turbo in assembled position when you get it out.
>Be VERY careful when opening opening the exhaust housing because it's likely to be seized and you have to hammer it a lot to break it free.
>There are some tiny little parts inside that could fly off if you open it suddenly.
>You have three little torx screws that hold the VNT mechanism. Definitely use some WD40 stuff on them and be careful not to round them.
I used a battery impact drill because it's not as brutal as a big one but still delivers well needed hammering to break them loose.
>Make sure you have a basic tap&die set because some studs might break.
You can make new ones out of STEEL (not regular, they rust) bolts, just cut the head off and make a new thread.


I've seen some writings that VNT turbos cannot be adjusted and that you need a flowbench or that you have to send it to the pro's....
Well to be honest I really don't wanna comment.
This is just how I did it and I suppose it's quite logical for anyone who works with cars but nonetheless.....

Take a look at the picture.
You see the VNT mechanism with the ring assembly located on the exhaust side housing.
now take your old CHRA, locate the pin and put it back onto the housing and move the actuator lever up and down in order to seat it into the ring and start moving the nozzles.
Move the actuator all the way it goes to the stop screw.
Now carefully remove the CHRA from the housing. Point is not to move the ring while you're doing it.
Shouldn't be hard.

So once you removed the CHRA use a flat screwdriver to mark a spot on the housing and on the ring. Press down the ring with your fingers and carve a line with the screwdriver on the ring and housing.
This will now tell you how the ring/nozzles should be positioned.
Now you take the NEW CHRA and place it on the housing just like the before.
Start adjusting the actuator stop screw until you hit the two marks to be flush against each other.
Might take a few take offs and ons.....

The nozzles don't close completely you see. That's why the stop screw's for. If you remove the screw, when the nozzles close the mechanism stops without the screw.
But the point is, the nozzles must be open a tiny tiny bit hence the stop screw.
This position is used to direct the exhaust gases at the tips of the turbine and spool it up quickly to a high speed.
At a high speed the nozzles open much more, thus removing the restriction, backpressure and the turbo doesn't sping so fast.


I did it this way and I have no problems whatsoever.
It's no rocket science but someone might appreciate the info.

https://imgur.com/yHZ6w5L
https://imgur.com/wXD6hOI
https://imgur.com/tp2u0ol

VNT turbo disassembly
How a VNT works
Don't buy cheap CHRA's. I bought mine from nerings on ebay which proved to be great with dhl shipping. (apsolutely no affiliation, just saying where I got it from).
 
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