VNT turbo geometry question - experts needed! - Alfa Romeo Forum
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(Post Link) post #1 of 8 Old 08-04-13 Thread Starter
Status: please help so wife will let me keep the alfa!!
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VNT turbo geometry question - experts needed!

Dear all turbo buffs.....

I have a question regarding the internals of the vnt turbo on the 147 jtd. I took mine apart to clean as I suspected I was having carbon build up problems (mcsf on high revs in 4th and 5th). Upon opening this was confirmed and I had the satisfaction of cleaning it up back to shiny however during dissassembly the three 3 m4 bolts that hold the vane plate inside the turbine housing sheared in the process arggrhrg! Annoying, anyway they are proving very hard to drill out and re tap due to limited access, here's my question....

Could I drill and tap new holes in the housing rotated exactly the right amount of degrees so that the vanes are relatively in the same place? Would that work? As far as I can tell the alignment pins on the main turbo core housing matches up with the outer housing directly and it doesn't matter if the vane plate is in 12 clock or 6 clock position.... I'm sorry I don't have pictures to explain.

Discuss ....
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this should help a bit for pics
Technical: jtd turbocharger - The FIAT Forum
http://www.fiatforum.com/gallery/dat...rehybri_6_.jpg
http://www.fiatforum.com/gallery/dat...forehybriz.jpg
http://www.fiatforum.com/gallery/dat...rehybri_4_.jpg
as for what your proposing im not sure
with the turbo in hand and a marker pen im sure you could mark out the position of the vnt nozzles and measure and mark control ring then try aligning the vnt ring rotationaly to see if they align again in between the original bolt holes
the control ring cant move but if your lucky the vnt ring might have more than 1 alignment
try in the tuning section also and for cost of a phone call a turbo specialist should put you straight(actually 2 on here somewhere)
tditurbo in here
https://www.alfaowner.com/Forum/tunin...project-2.html
ive tried to knock up a paint image for you, basically you need to keep the relation of pin and vnt ring cut out in the same place and see if rotating the actual vnt ring to say the white rings and see if looks the same?i cant remember if the actual vanes are all the same angle so moving to the next drive lug may screw it all up.
https://www.alfaowner.com/Forum/attac...1&d=1365458425
be aware any inaccuracy in the hole drilling will totally screw the turbo probably, also if the vanes do not match 100% original open/close amount it may totally screw how it runs.

Last edited by sussexa; 18-04-14 at 18:35.
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Is there anything i should be carefull about when taking turbo apart for cleaning?
Tx
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(Post Link) post #4 of 8 Old 31-08-13 Thread Starter
Status: please help so wife will let me keep the alfa!!
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Yeh, don't shear any bolts off! Turbos get very hot so you can bet they will be pretty much 'welded' in by now, plenty of penetrating spray and lots of patience....

Also the spacers that hold the vane plate in place are very small and could be lost easily. Apart from that it comes apart relatively easy and only goes back together one way thanks to the clever locating pins so you can't go too wrong.

Good luck!
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Is there something that blocks blades before opening? Do blades have to be in some position before you can put all together?
tx
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not fully open, otherwise all is good.
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tyvm for all help ill report when done
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