AHU with VNT, No VNT Control

jackfolstam

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MkI Rabbit ALH swap
I just bought a Caddy with what I think is an AHU MTDI in it. I've done a Rabbit with ALH swap and don't know much about the AHU.

t's got a VNT15 on it, with nothing hooked up to control it. Since this thing has an exhaust, oil lines, intake, intercooler piping, etc I'd rather not change it all out for a different turbo. Can I run the VNT15 without controlling it and damage the engine?
If the vacuum actuator thing is sitting at rest I'm thinking it is making very little boost, not full boost?
The pump has a vacuum line from the intake hooked up. If it sees only atmospheric or what little boost this thing is making will it defuel all of the time?
I haven't driven it around due to massive coolant and engine oil leaks. Previous owner (he didn't build it) said gauge said it makes 14psi. That's atmospheric right? The gauge line was on a T between the intake mani and the pump (which I have removed).
A quick search reveals it's not impossible to make it work, I'm part way through a thread where a guy plans to make an Arduino controller for it.
The TB cover says AHU, could someone have put the cover on there, or just the sticker, to fake having a TDI just to sell?
The head looks like an AHU with a Land Rover pump on it, and I can't find an ECU. There's no way to put an AHU head on a 1.6 right? It sounds like a 1.6, nothing like my ALH.
I can't find a displacement casting on the back of the block.

(pics were taken at night, sorry)
Is the CCV the same on ALH and AHU? it doesn't seem to fit well here and I think is the same as on my ALH.


The main question is, will not controlling the VNT15 damage anything?
 

jackfolstam

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I also see that there are supposed to be three studs holding the valve cover down, where I have a bolt in the middle. I'll correct that soon since the valve cover leaks. I already replaced the gaskets under the studs and tried to replace the seal around the valve cover, but couldn't pull it out when tugging really hard on the half moon part with some big pliers. They are replaceable, right? It definitely leaks a lot. I don't want to screw up the cover by trying too hard.
 

My_name_is_Rob

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I also see that there are supposed to be three studs holding the valve cover down, where I have a bolt in the middle. I'll correct that soon since the valve cover leaks. I already replaced the gaskets under the studs and tried to replace the seal around the valve cover, but couldn't pull it out when tugging really hard on the half moon part with some big pliers. They are replaceable, right? It definitely leaks a lot. I don't want to screw up the cover by trying too hard.
Yea they are replaceable. Fairly reasonably priced too if i'm not mistaken.
 

jackfolstam

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Yea they are replaceable. Fairly reasonably priced too if i'm not mistaken.
Thanks. I just have to remember to be reeeeaaaaal careful to not drop the stud seal down into the cylinder head when taking the bolt out next time...

So this thing must be making some amount of boost, because it blows off the intercooler pipes at the silicone-to-exhaust-pipe connections: no barbs.
 

KLXD

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'98, '2 Jettas
Atmospheric pressure is around 14.6 psi absolute meaning referenced to 0 or "vacuum". Unless your gauge says otherwise 0 would be atmospheric and you're getting 14 psi manifold pressure. Or 28.6 absolute.

I was recently educated that a VNT sits at full boost with no vacuum applied so you basically have no boost limitation.

Like pulling the pressure line off a wastegate actuator.
 

Vince Waldon

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If you go over to vwdiesel.net there are a couple designs for mechanical VNT controllers floating around... look for one by Andrew Libby in particular.
 

Hasenwerk

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1982 Cabriolet (BEW|VNT17|Stage4), 1989 VW TriStar Syncro soon-to-be CR TDI (CBEA), 2001 Ford Ranger Edge 4x4 (ALH|VNT17|R520|Stage4)
Thanks. I just have to remember to be reeeeaaaaal careful to not drop the stud seal down into the cylinder head when taking the bolt out next time...
So this thing must be making some amount of boost, because it blows off the intercooler pipes at the silicone-to-exhaust-pipe connections: no barbs.
No barbs - that's a problem for sure.

Quick-n-dirty solution:
Get some short, round head #6 screws, drill holes 120 degrees apart and install the screws at the end of the pipe - this way the clamp has something to hold on to.
 

jackfolstam

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Atmospheric pressure is around 14.6 psi absolute meaning referenced to 0 or "vacuum". Unless your gauge says otherwise 0 would be atmospheric and you're getting 14 psi manifold pressure. Or 28.6 absolute.

I was recently educated that a VNT sits at full boost with no vacuum applied so you basically have no boost limitation.

Like pulling the pressure line off a wastegate actuator.
You learn something new every day.

No barbs - that's a problem for sure.
Quick-n-dirty solution:
Get some short, round head #6 screws, drill holes 120 degrees apart and install the screws at the end of the pipe - this way the clamp has something to hold on to.
Thanks; never had that idea. I did pinch some aluminum pipes before with pliers to make barbs, and welded a bead on exhaust tubing.

So think it is a problem to run with no VNT control?
 

Hasenwerk

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I am going to disagree with KLXD

If you remove the vacuum from a VNT Turbo the vanes go to a no boost situation as opposed to a full boost situation. This is self-preservation if something goes wrong.
 

KLXD

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That's what I figgered but was told otherwise. I'll have to search up the thread.

Maybe I'll go look at the '2.
 

jackfolstam

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If you remove the vacuum from a VNT Turbo the vanes go to a no boost situation as opposed to a full boost situation. This is self-preservation if something goes wrong.
I was hoping it was that way from the start. Otherwise, the PO and whoever did this swap would have done some damage to the engine. Plus, it's really slow. An additional note, the turbo whistle at idle (the only time I hear my own cars from the outside) does sound just like my ALH car.
 

jackfolstam

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I just met a fellow TDI'er at the junkyard and he told me that the VNT15 defaults to max boost, "opposite the 1.8T," he said. That's a fact I have yet to, but will, check. I believe him since he amongst other things is a Malone dealer, owns way too many TDIs, and actually sold the PO of this truck some parts. Small world. He even knew the truck by my engine description, not by the owner's name.
 

Hasenwerk

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I just met a fellow TDI'er at the junkyard and he told me that the VNT15 defaults to max boost, "opposite the 1.8T," he said. That's a fact I have yet to, but will, check. I believe him since he amongst other things is a Malone dealer, owns way too many TDIs, and actually sold the PO of this truck some parts. Small world. He even knew the truck by my engine description, not by the owner's name.
VNT15/17 in stock form, if you remove the vacuum, they go to the "no boost" position.
 

jackfolstam

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VNT15/17 in stock form, if you remove the vacuum, they go to the "no boost" position.
At idle the gauge bounces around 0, and then cruising on the highway something like 20psi.

What if I remove the vacuum diaphragm, set the vanes to something in the middle, then put a manual boost controller set to the VNT15's max?
Is the turbo more responsive at higher RPMs (highway) how it is now, and would spool faster at lower RPMs (off the line) the more the lever is actuated?

I went to the junkyard and picked up what I believe to be an ok condition AHU turbo, manifold, downpipe, intake plumbing no air box, oil feed line, and oil drain line. I understand I can just connect the wastegate to the turbo and turbo control is done?
 

Hasenwerk

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Buy a holset turbo with a waste gate. That will solve your issue with 1z ahu and mtdi alh. Not the cheapest solution, but the best solution for running 20th century injector pumps.
 

jackfolstam

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Buy a holset turbo with a waste gate. That will solve your issue with 1z ahu and mtdi alh. Not the cheapest solution, but the best solution for running 20th century injector pumps.

Thanks for the advice but unfortunately I just don't want to buy another turbo; I'd like to make do with what I have. I also have a T3 and everything but an oil feed line sitting around from years ago as well, not too keen on swapping to the oil pan that leaked. I'm thinking the path of least resistance is to manually set the VNT. Today pulling up a hill it maybe hit 20psi, 55mph is 10psi or so. I'm sure the K03 would have better driveability and probably worth the effort of plumbing it.

Just, are there any caveats to putting the K03 on? Is it a dog with the stock wastegate setting? How bad is it to hot pipe it (no intercooler)?
 

Owain@malonetuning

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K03 makes solid bottom end torque and will hold 18 psi as well. A K24 or T3 from a 1.6td would be more fun power wise if you can find one kicking around. Manual VNT controllers work, but can be a pain to setup. OBD + electronic timing diagnostics are worth the wiring and you can run much larger VGTs that'll spool like a k03. Mark personally ran a k03/k04 hybrid ASV (AHU) in his mk3 for years @ 22 psi, really solid setup and would probably go for that personally. You'll benefit from an intercooler on all of these setups, bring boost down around 12-15 if not running one.
 
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