Putting a VNT 15 on a Rabbit

Post by **Fatmobile** » Thu Jul 23, 2009 11:44 am

I got a VNT turbo in the back seat of a car I bought several years ago,.. fixed the gasser up and sold it but kept the turbo.
Andrew and others have inspired me to figure out how to control it and put it on something.
imageshack sucks I had to rehost all the pics and repost them so the process/order is a little different than when I was first learning.

Here's a view of the rear with the turbo and intake mounted:

A view from the top:

The plan is to use the vacuum can, that is normally controlled by computer, as a boost can.
I didn't have to do anything to the can except hook it up to boost instead of vacuum, as I step on the accelerator it presses on the can while closing the vanes for more power.
As the boost builds; both boost and the can's internal spring push back against the accelerator rod. Forcing the vanes to open again.
The rod coming from the injection pump has a spring in it that allows some give.
There is alot of adjustment built into the lever so I should be able to adjust how easy it is for the boost to push back against the rod/spring by moving the attachments in their slot.
There is also a slot the lever can move on to help change the curve.
The spring compression on the rod can also be adjusted or the spring replaced.
The lever is made from a shift lever from a trany.
Oh yeah, that's what I do with old heat shields. Drill them out to 1/4" and use them for fancy washers. They look great on the old A1 timing belt covers too. Don't throw them away:D
This isn't mounted on the car yet. I need to clean the intake and exhaust before mounting and fitting the hoses and lines.
Any feedback would be great.

rabbit_man · Post by **rabbit_man** » Thu Jul 23, 2009 7:06 pm

So when you floor it say, with the engine off, it will completely squish the spring in the can? Seems like that be a little hard to push the pedal.

What is that intake off of? I can't see the whole thing in your pic, I'll be drilling a hole like that too. I haven't put the controller on yet, I've been having troubles getting more than 3-4psi of boost. Here's my threads:

http://www.vwdiesel.net/forum/index.php?topic=19458.0

http://www.vwdiesel.net/forum/index.php?topic=20054.0

BTW, what is the A/R's of your turbo? Mine is a euro vnt from a 110hp AFN and I'm almost sure it's setup to boost different than the ALH.

Looks like yer havin' fun

Post by **Fatmobile** » Thu Jul 23, 2009 9:52 pm

I'm not sure what trim it is,..
not sure how to find out.

I also don't know what intake that is,.. I'm guessing A1 gasser.

It should completely squish the spring in the can when floored,... except boost should also be added to the spring pressure to back the vanes off when boost gets too high.
The spring being used is a brake shoe spring, that limits the pressure on your foot. I haven't felt it yet but I can't imagine it ever bottomed out.
I'll probably end up with a longer spring,.. or stack them.
I should take a picture of how I clearanced the egr port.
I used the block-off plate to bolt to the intake so they support each other,.. like all the NA VW diesels do.

rabbit_man · Post by **rabbit_man** » Fri Jul 24, 2009 4:28 pm

My turbo says the A/R numbers on the intake and the exhaust sides.

rabbit_man · Post by **rabbit_man** » Fri Jul 24, 2009 7:54 pm

The thing that's weird with my turbo is I can't put the can directly on the turbo where it's meant to go, the actuator lever is between the turbo and block and unlike US vnt's, the boost can on the euro spec vnt sticks up instead of down and would hit the intake mani really bad, that's the main reason I was gonna drill a hole through the intake like you did.

Keep it up, I'll be following this thread!

libbybapa · Post by **libbybapa** » Fri Jul 24, 2009 10:12 pm

I like it although I'd have two concerns. It is very much the same concpet as the first couple vane controls I made. My first concern is that the pedal would be hard to press. The other concern is that the vanes would stick. You will be striking a balance between the pressure of the spring on the accelerator rod and the pressure of the boost and can spring. Because of the variable resistance to vane motion, that balance will change and could eventually result in vanes sticking. The more recent vane control concept I've been working on should eliminate both of those concerns.

http://www.vwdiesel.net/forum/index.php?topic=19398.0

Definitely keep us posted on how it works.

rabbit_man · Post by **rabbit_man** » Fri Jul 24, 2009 10:50 pm

A few minutes ago I operated my vane lever by hand while it was running and revved to about 1500rpm, as the vanes close the exhaust gasses help pull them shut.
When they're fully closed it is hard to open them without jerking it. So I wonder if the boost can would jerk them open too?

About them sticking, I haven't been running a controller so the vanes sit still, but every week or so I mess with the vanes by hand and they've not been stuck yet, sometimes they're slightly stiff on the first stroke though.

Post by **Fatmobile** » Fri Jul 24, 2009 10:59 pm

Yeah, still lots of installing and fitting,..
and several other projects.
Since it will be modulated by boost; a boost controller could be used with it to kick it back into your foot whenever you hit a set point.
You could feel it in your foot when boost gets too high.

Andrew: I took a look at the link you posted.
I see how it eliminates the spring in the line between the accelerator and VNT.
I was thinking there has to be some give so when boost gets too high the vanes can be opened.

We all want to see how much pressure this will put on the accel peddle.
The more pressure on the peddle, the less chance it will stick.

libbybapa · Post by **libbybapa** » Fri Jul 24, 2009 11:33 pm

I think perhaps there is some simplification and added reliability that could be had by a combination of both. I like that you are using only the boost/vac can spring as the return spring for the vanes, and like that the other concept eliminates the spring in the rod from the accelerator lever. I'll have to do some more thinking...

Post by **Fatmobile** » Sat Jul 25, 2009 12:52 am

Ahhh, payback.
If I can manage to make you think as hard on this as you've made me think about a few things,
then that'll be some satisfaction.

This design was partially inspired by what you posted in the link.

It's my favorite project right now. Wish I could work on it every day.

I have learned a few things about rods and levers.
Heim joints don't normally use 1/4 20 threads.
More like 1/4 28,... so they won't work with these rods.
I did find a local source for them and will get a die or the proper allthread next time.

Post by **Fatmobile** » Mon Jul 27, 2009 12:58 pm

OK, after looking at your drawings again and seeing rabbit-man's design on the GTD forum,.. I think I can do better
Sooo the drawings in your link inspired me to build one using levers and rods but I didn't realise the complete goal until now.
I think I can do better at making it a solid connection between the pump and turbo vanes,.. and still allow boost to back the vanes off, with little added pressure at the peddle,...
and salvage some of the parts from this one to do it.

Post by **Fatmobile** » Fri Jul 31, 2009 12:38 am

Any idea where to put the EGT probe?
Something that should be done before I bolt the turbo into the car.

Post by **Fatmobile** » Sat Aug 01, 2009 12:21 pm

Here's a picture of how I connected the intake and exhaust, so they support each other:
imageshack sucks

There will be another bar going from the support hole on the turbo to the back of the block,... I don't want any problems with exhaust studs breaking.
imageshack sucks

That's my new controller idea.
As the rod is pulled by the accelerator peddle it closes the vanes.
The vacuum can was turned into a boost can by compressing the spring,... using a valve spring, the spring seat is a gasser upper timing belt cover nut (CIS I think).
Now when boost comes up it should back the vanes to the open postition.
I have heim joints on the way to go with the 1/4 28 allthread I found locally at fastenal.
The accelerator is solidly connected to the vanes but influenced by the boost can.
Less pressure pushing back against my foot is a great goal,.. I didn't really pay attention to how much pressure is against my foot before Andrew pointed it out. I don't want any more than there is now.

This controller was later replaced by one that sits above the intake

I have an idea on a good place to put the EGT probe, I'll take pics when it's done on.

rabbit_man · Post by **rabbit_man** » Sun Aug 02, 2009 2:24 pm

Looks pretty good, with some tuning that'll probably work fine.

Post by **Fatmobile** » Sun Aug 02, 2009 9:08 pm

Thanks, I was pretty sure it would work but it's nice to have some feedback from someone who knows what I'm aiming for.
... and I know you've been through this and understand it.

The boost can could be pulled apart and flipped instead of adding another spring,.. but I think the extra spring holds the pivot point more firm. Not sure on that but the can plunger is pretty stiff.