VNT15 Questioins

can I put the manifold from an early VNT15 on a later model stamped GT1749V? I think my earlier one is just marked VNT15, came off a 1999.5 Jetta. I took the original turbo apart when I got it and got the vanes all freed up. Then, I found a GT1749V in the junkyard. cleaned that up, and replaced the original turbo. But, the little vane actuator finger inside the turbo is worn down some and creates some play in the GT1749V.
So is the geometry of the turbos the same on the manifold side, or not? can I make one better turbo out of these two? Or should I just live with the worn out vane finger?

The "vane finger"can be welded up and Dremeled back into shape to stretch the life some. Is the ring wear mirroring the finger's?

They are same turbos, so it can be install in any ALH engine.

jetta said:

They are same turbos, so it can be install in any ALH engine.

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I bolted on the GT1749V no problem to my engine, thanks.

My question is, is the cast iron half from the earlier VNT15 the internally the same as the later VNT15? Like the contours and shape and flow and stuff, like performance wise.

JETaah said:

The "vane finger"can be welded up and Dremeled back into shape to stretch the life some. Is the ring wear mirroring the finger's?

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All of the vane levers looked fine in comparison to the main one. Not sure if they were worn, I was fixated on the one.

That main one is the one that will take the hit along with the corresponding ring pocket.

I don't recall seeing any wear on the single ring pocket.
Is it hard to weld the lobe? Would it not get welded to the part it's resting in? Or can you remove it?

I got my second P1550 boost deviation code yesterday after a few weeks with the "new" worn turbo. After the first code I was hoping that adjusting the vacuum actuator arm length would help. The first time it hit the code it was obvious, I was pulling up a long steep hill and suddenly power was limited. But, since there is wear on the vane finger, I guess hitting a bump in the road could cause the vanes to move unexpectedly, causing a boost deviation.

The second time I was just cruising down the freeway and noticed when I went to merge on the interchange I didn't have full power.

I'm guessing the only way to solve the issue is to repair or replace the turbo, since the vanes could just move at random. I assume it's the turbo, since this hadn't happened in the 8 months I was driving around before swapping turbos.

I hate to ask, but are absolutely sure you did not put the control ring in upside down? If you did that will definitely cause a lack of boost.

EDIT: I just re-read your last post, likely not upside down control ring. You could quite easily weld up the control ring slot as one solution, what is your N75% at WOT in third gear, is it significantly higher or lower than 65%?

I see now, weld up the ring instead, that is different train of thought...

I just got a KII cable, so I'll have to get a laptop now...

I've got an old log from when I rented a cable once, unfortunately it looks like I got N75% and RPM, and not throttle percent. But, it looks like N75 got to 58.6% on one full throttle pull and 55% on another, but I changed the N75 since then trying to troubleshoot limp mode. I had a new ebay vane actuator on the original turbo, and now I have the one that came with the GT1749V which seems to work fine on a mityvac.

Your N75% is a bit low, 65-70% at WOT is what you are looking at. Please remember the N75% on an ALH is backwards thinking: a reading of say 10% means the N75 is applying full vacuum to the actuator, and a reading of say 90% means the N75 is trying to bleed the vacuum off as fast as is possible. with a reading of 55% I would say your control ring/actuator nub--albeit worn--is still moving the vanes quite far enough.

The actuator arm needs to be longer to raise the N75% value.

A GT1749V is a VNT15.

jackfolstam said:

I bolted on the GT1749V no problem to my engine, thanks.

My question is, is the cast iron half from the earlier VNT15 the internally the same as the later VNT15? Like the contours and shape and flow and stuff, like performance wise.

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To answer your question, yes.. They are the same inside.. The biggest difference is the lower support bracket bolts on differently.

jackfolstam said:

I see now, weld up the ring instead, that is different train of thought...

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You may have to weld and shape both ring slot and finger to restore it to a like new condition.
The finger and ring don't always fall in the same plane when assembled in the turbo so check both sides of each to see if they are notched.



Both parts take a hit when the mechanism starts to jam up.

Nevada_TDI said:

The actuator arm needs to be longer to raise the N75% value.

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Thank you; I did adjust it out a little further after reading other similar posts, but I'll adjust it further and see if that helps. I've been limiting my foot from full throttle lately, and it's not easy with the 11mm pump I just installed...

turbocharged798 said:

A GT1749V is a VNT15.

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I'll check the part number early next week for my original turbo, but I thought that there's the GT1749V, the GT1746 something, and another model before that, each with the overarching name VNT15? I noticed a huge difference in turbo spool noise between my original turbo off of a 99.5 Jetta (don't have the part # readily available), to a GT1749V (don't remember what model/year it came off of).

TDIJetta99 said:

To answer your question, yes.. They are the same inside.. The biggest difference is the lower support bracket bolts on differently.

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Thank you very much! I have the bracket, and a brand new updated oil return line and union. I will be mating the old (less worn) manifold with the newer GT1749V shortly! ...but what does that say about the possible wear on the cartridge side of the GT1749V? Nevermind, I guess ignorance is bliss.

JETaah said:

You may have to weld and shape both ring slot and finger to restore it to a like new condition.
The finger and ring don't always fall in the same plane when assembled in the turbo so check both sides of each to see if they are notched.
Both parts take a hit when the mechanism starts to jam up.

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I just took apart another junkyard turbo tonight and saw exactly what you are talking about. It looks like I took your photo. So the turbo I installed though has, dare I say, double that wear. The one I just took apart looks like the one in your photo. Is it worth it to swap them? $20 in gaskets, plus disassembling either the lower part of the car to pull the turbo out, or the intake side of the engine? Or don't bother and keep it as a backup?

turbocharged798 said:

A GT1749V is a VNT15.

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Yes and No

Normally a gt1749v has a different (updated) vnt mechanism vs the VNT 15.


However ,very early gt1749v ('97-'98) have a vnt 15 mechanism, but a compressorhousing with gt1749v.

TDIJetta99 said:

To answer your question, yes.. They are the same inside.. The biggest difference is the lower support bracket bolts on differently.

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Do you happen to have any proof like a link or document, or did you learn this from word of mouth on the forum? Thanks.

jackfolstam said:

Do you happen to have any proof like a link or document, or did you learn this from word of mouth on the forum? Thanks.

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I learned this from working on these cars for a living for more than 10 years.

TDIJetta99 said:

I learned this from working on these cars for a living for more than 10 years.

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Thanks. I think I will take the better looking manifold from the 99.5 turbo, and put it on the 2002 turbo I posted the pics of.