(Diesel) Mechanical VNT Turbo Vane Control

[?Waldo?]

For quite a few years I've been playing with the VNT turbos on various engines. In another thread I think it was Wailliam Taylor who asked me about my mechanically controlled VNT vanagon installation. I finally got around to taking pics and figured I'd post them up. The various vane control designs I've done have gone through significant changes but all maintained the same design goals. Keep the vanes normally open, close them proportional to the demand for power, over ride the vane position and open them in order to not exceed max desired boost. I have to say the last couple iterations have been ROCK SOLID.

I have been using a VNT15 on my 1.6TD and have been regulating it to 16psi. Initially I had it set higher, but I'm more concerned with engine longevity than I am with eeking out more power. As is, power significantly exceeds that of a stock 2.1 WBX. On my van, the boost response is absolutely incredible. I live at 7,000' of elevation where spooling is significantly slower than at see level and yet I can be at 5psi while I let the clutch out. At low rpm, the boost will snap right up to 10 psi (where I have the control starting to kick in) and it moves up to 15-16 psi as rpms increase slightly and stays there.

With early designs I had some trouble with the vanes sticking from carbon buildup. With the current design that is not an issue. In fact with the installation on my wife's '82 Merz 300TD, when I removed a previous control, the vanes were fairly well stuck. I worked the vanes by hand and freed them up a little. After driving with the updated control for a few days the vanes were like butter. Absolutely no resistance.

Here are a few pics:

Because of the intercooler pipes being in the way, it is pretty much impossible to get a decent picture of the linkage that runs down to the vane lever on the turbo.

The spring mechanism in the last pic is to allow the pump accelerator lever to return even if the boost can is fully expanded and vanes pushed fully open. For pics of the one on my wife's car, go here. That control is basically the same concept, but laid out in a way that might be a little easier to understand. One significant difference between that control and this one is that on that one, I used a manual boost controller and check valve to control max boost which with the considerably larger intake tract volume works fine with that application. I found that wouldn't work on my van as the controller did not react fast enough and so boost would spike up to 25+ psi and then snap back to the setting of the controller. Instead, I exchanged the spring inside the boost can for one with the appropriate rate/length/diameter and the boost signal is sent directly from the charge pipe right before the intake manifold.

Great care was taken to make sure the lever arms were the right length, linkages had adjustment where necessary, angles were correct, nothing rubs where it shouldn't, slop in the control is totally minimized, heim joints were used at each joint and the lever that changes the linkage direction is bushed with a nice fitting bronze bushing.

The VNT is like having your cake and eating it too. It gives the super fast boost response of a tiny turbo and yet flows more freely than a large turbo (that would be obnoxiously laggy) when the vanes are opened.

[a914622]

Thats SWEET!

Are you running the TDI cam? you have sparked my intrest in the VVturbos. Iv always thought the 1.6t have a lot more in it.
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87 gl powerd buy 2.5subaru
75 914 getting 2.2t subaru scratch that SVX subaru

[?Waldo?]

It has the stock 1.6TD cam. The engine is internally stock aside from arp fasteners for the head bolts, rods and mains and the MLS AAZ head gasket. The injection pump fueling is well tuned. I tuned it to a very slight haze at full pedal at the range of rpms and boost pressures. I then turned it down so that there is not any visible smoke and EGTs will hit 1400° at full power on an extended grade. EGTs are measured pre-turbine. A large part of the increase in performance with the later engines lies in intercooling and the turbos.

[jackbombay]

Nice work! Where did you get the diaphram?
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[a914622]

I tryed a TDI grind cam on a fresh rebuild. The power band was lowered about 800 rpms. The stock turbo didnt boost low enough and ran out of boots a little early.

thanks

jcl
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87 gl powerd buy 2.5subaru
75 914 getting 2.2t subaru scratch that SVX subaru

[?Waldo?]

[Vanagonner]

True genius- as simple as possible, and beautifully executed. I also appreciate that you are doing this on the 1.6. Not many people understand that it is a great engine in it's own way. And with no smoke! Please let us know what kind of fuel economy you get with it as you go. Congrats on a successful outcome from your persistent efforts.
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Sage
'82 Westy 1.6 D
the mighty n/a

[?Waldo?]

I don't have any decent fuel economy numbers. I've been running taller tires and so the speedo and odo are off. I haven't had a chance to find out how far off they are.

[xoo00oox]

Nice work. I know you put tons of time in this project, I had enjoyed watching it on vwdiesel. I have a few spare VNT's here and will use what I have learned from your posts when I get a chance to put them on something.

[a914622]

I was using a TDI grind- 1.6 hydrolic head. It added a lot of bottom end tork.
Im working on putting together anouther engine with ported head, total seal rings and ARPs all around. Im going to keep an eye on this because im thinking this turbo is the final part Iv been looking for.

jcl
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87 gl powerd buy 2.5subaru
75 914 getting 2.2t subaru scratch that SVX subaru

[rmcd]

Do you know if anyone sells a turbo, manifold and pump setup or should I just resolve myself to following Andrew's lead and building my own?

Anyone had any experience with fin-turbo.fi?
TIA.

[markd89]

I think you'd have a market if you decided to produce a kit

[?Waldo?]

I've considered it but am currently more than busy enough. Maybe in the future. A big hurdle is that the typical VNT 15 seen in the U.S. severely interferes with the driver's side aluminum mounting bracket. I used a Euro VNT 15 wit a custom adapter to the stock 1.6TD exhaust manifold. Those turbos are harder to source in the US. The typical US VNT with integral exhaust manifold would require a custom driver's side engine mounting bracket as well. The whole package with turbo would be quite expensive. Then again, the low-rpm performance improvement is priceless.

[Syncroincity]

I was hoping you'd put this up here.

I just scored a brand-new VNT-15, the Euro version with no manifold... it has the inverted (vs. an AAZ, anyway) triangular exhaust interface. I have the earlier trapezoid manifold, I'll have to work out an adapter.

Does someone sell a prefab VNT exhaust outlet flange for custom pipe work?

Do you have the photos of the earlier incarnation that had been on VWD.net? Some of those were great for grasping the concepts here, particularly the hollow tube & spring arrangement for the boost can vs. fuel lever compensation.
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'86 Syncro CHC Top AAZ Turbodiesel
'04 Passat Variant 4Mo 5MT

Vanagon Build: http://www.thesamba.com/vw/forum/viewtopic.php?t=466866&highlight=

[?Waldo?]

I don't know of anyone selling pre-made flanges. Let me know if you come across someone. I've had to make my own.

I have some of the older pictures, but wonder if they wouldn't just add confusion rather than clarity. Here are some concept diagrams to assist in easy understanding of how the control works.

[Syncroincity]

Perfect, thanks!

I found a guy on TDIclub that does the flanges, with or without an expansion cone; username "Whitbread"... Matt Whitbread he runs a VW fab shop in Lima Ohio. Beautiful work. The flanges are about $40.

http://forums.tdiclub.com/showthread.php?t=247135

I'm tempted to just ship the mani & turbo off to him, or make a roadtrip once I get the beast on the street... I'm running the T2 for the time being until after break-in.
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'86 Syncro CHC Top AAZ Turbodiesel
'04 Passat Variant 4Mo 5MT

Vanagon Build: http://www.thesamba.com/vw/forum/viewtopic.php?t=466866&highlight=

[a914622]

Sweet . I think i just scored a vnt-17, so the build is on. Now i need to find a vacuum can in figure the linkage.

Oh yea an intercooler too.

jcl
_________________
87 gl powerd buy 2.5subaru
75 914 getting 2.2t subaru scratch that SVX subaru

[jackbombay]

[?Waldo?]

You can use the stock vacuum can, but need to turn it into a boost can and fit it will an appropriate spring or the boost curve might not be desirable. Prothe sells new TDI vacuum actuators made in China for about $45 shipped on eBay. As mentioned previously, I used one that came with my turbo, sliced off the crimp with a grinder and drilled the eight tiny holes around the rim and screwed it back together with mini nuts/bolts from the hardware store.

For the spring on that control I actually used trial and error with my collection I've gradually accumulated over the years. That said, you can measure the size and calculate the spring rate and amount of pre-compression necessary for the desired max boost and order from places like McMaster. That particular boost can diaphragm has an area of 5.3 sq-in. Given that the can has 0.5" range of motion and to start regulating at 10 psi and have vanes full open at 15 psi at max pedal position then you would need a pre-compression of 53 lbs (area 5.3 sq. in. x 10 psi = 53 p) and then the spring rate would need to be 26.5 pounds per inch (53 p x 0.5 in range of motion). Given that the fully compressed length would be say 3/8" then the total spring length would need to be 3/8" (fully compressed length) + 1/2" (rod travel) + 2" (pre-compression of 53 lbs) = 2-7/8" length and 26.5 lbs per inch rate with the ability to compress to 3/8". You can also have two springs and size them so one is inside the other in order to get the desired pressures but the math can get more complicated.

Calculating the lever arm lengths (attachment points of the heim joints) is also a bit of a process that I will describe in the future when I have more time.

[avocado_tom]

Any possibility of these photos being restored?

Or is there somewhere else they live?

Much obliged!