2LT VNT turbo upgrade

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Oct 12, 2022
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Hey guys. I'm still pretty new here. I posted a short introduction thread for my 87 2lt Pick-up in the other forum section, but I see most of the diesel gurus hang in here mostly.

As stated in my other thread, my turbo feels and looks a bit tired. It blows lots of oil in the boost pipe and barely makes 10psi with the wastegate completely disconnected. I could simply replace it, but an upgrade sounds a little more interesting as I'd like to make the thing a little more responsive. TD04 look to be the prefered option here, but what about VNT turbos? I know controlling them is a bit different to wastegated turbos. I spent a few hours today thinking about how to use a mac valve and an Arduino to control the actuator using the truck vacuum reserve and then I found out VNT specific MBC are a thing.

Do you guys see another road block I might have missed in retrofitting a ''modern'' VNT turbo like a GT18V to a 2LT?

Thanks in advance!
 
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I think you can control a VNT very simply with vacuum, boost and some bleed valves. But I've never actually got to try it.

I had a custom GT1856V built up for my old work car (2.2L 16V diesel). But I couldn't get enough fuel from the injection pump to make it worth fitting. So I just ran the GT1549 wastegated instead. The GT1856V is still here looking for a new home.
 
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Yeah. This is pretty much what de GFB boost controller is. it taps into the vacuum to actuate the VNT actuator and uses boost in relation to pre-turbo pressure to control rise rate and maximum boost. I could maybe use a few bleed valves connected to one another to make the same thing if I want to spend time figuring it out.

That GT1856 is pretty sweet! probably a bit much for what I am looking to do. I see a lot of Renault Espace 2.2DCI GT1852V on Ebay. I like its vacuum actuator and overall packaging. I can weld and design flanges to make it fit better.
 
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Biggest thing with a VNT fitment is orientation. Most of them can't be clocked on the turbine side so you've got to put up with where the ports come in.
 
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Yeah. Because of the vane system... Altough I wonder if you could remove the outer ring that moves all the vanes and put it back where the groove where the actuator ''cam'' is at another angle. Then put the CHRA back in. That would mean you can rotate the turbine housing every 360 degree/number of vane.

Looking at the GT1852V, that could be needed so it doesn't sit too high for the bonnet to close.
 
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Yeah low mount ones are hard to find. I tried to clock a Mercedes one with the inlet on ~45 degrees and would have to relocate one of the rollers that supports the vane ring. I then realized it was too small for my plans anyway. Still got that one too.

The nissan one they put a zig-zag in the actuator can so everything would clear the manifold above:

Nissan Almera YD22DCi Turbo.jpg
 
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Yeah I see. This configuration would be hard to fit in a 2LT. Here's what the Renault Espace turbo looks like

1667056710597.png

The actuator is in a good spot. I could maybe make it work with the stock housing orientations, but it would be nice if I can clock them round 60-70 degree. At firs glance, the turbine housing is held by these bolts and washer. If the picture of the inside I saw was right, it has 11 vanes, so I'm hoping it can be clocked every 33deg. I bought one yesterday so we'll see one it gets here!

I also found a little more info on how the GFB actuator works on a Patrol forum and how to reproduce it with cheap needle valves. I might try that instead. It's not the optimal way to control a VNT turbo as I was thinking, but that'll work until I decide I want something better. And since my truck is an old rust bucked, the saying that temporary solutions are the most permanent may very well happen lol
 
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VNT turbos can be clocked on the turbine side, but like mentioned only in increments of 360º/#vanes, and some of the places are already taken by the roller guides for the vane ring. I did this to the GT1749va I put on the TDI in my Prado to run it as a high mount turbo instead of a low mount one. The biggest issue I ran into was relocating the actuator so that it still functioned properly. In my case I was able to modify the actuator bracket and use an actuator off a different turbo to make it work, though I think it is still slightly out of adjustment.

Also, there is probably a little locating pin that insures the turbo is assembled in the correct orientation, that will have to be removed. I found that the easiest way to get the turbo assembled at the correct angle was to draw a template in CAD, basically a circle with an OD the same as the CHRA, divided into 11 sectors. Printed 1:1 scale and overlaid onto the turbo housing, I could then make a little mark on the outside of the housing to line up the CHRA before bolting it all together. I used a little notch cut into the paper template to line it up with the locating pin hole.
IMG_0620.jpeg
 
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Yup. That's pretty much the process I went through. I didn't think of doing a template. That's a neat idea! I will keep that in mind if it appears that my clocking is a little off.

Thank you
 

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