Another VNT controller

[fatmobile]

I put together a couple VNT-15 Rabbits this summer.
 One for a friend with an 11mm, 1.6,.. I didn't want to leave the vanes tied closed with no control over the pressure.
 I wanted the boost to push the vanes back open when it got to around stock TD boost pressures.
 First I turned the vacuum can into a boost can:
 

The spring is a valve spring, the spring seat is from a timing belt cover on,... this one was from a Fox.
It needs to be ground down enough to fit inside the can mount bracket to allow maximum stroke:


Here it is mounted to the turbo:

 I bolted one end to an extended bracket so it would point away from the stock vane controller lever.

 The rules Andrew put forth were that there should be no spring working against my foot. Before that I hadn't paid much attention to how much the stock setup pushes back against my foot. On long trips it's bad enough as it is, and I wouldn't want any more pressure.
 The other rule was to have a direct connection to the vane controller, to provide enough force to keep the carbon from building up and causing the vanes to stick.

 So the boost-can acts like a pivot, but doesn't push back against my foot when boost builds,..
 but when the boost gets high the pivot point moves forward and pushes the vanes back closed.

Rods and levers lead back to the lever on top of the pump.





 It regulated the pressure to 12psi max and the car was incredibly fast even at 12psi. with a big boost leak I couldn't find before he took it back home (he found it later, I forgot to put a plug in of the 1/4" NPT holes I tapped 
Boost climbs steadily, right along with my foot.
 I got it built and didn't tighten the oil supply line enough so it started leaking on his way to Cali,.. Joe made several attempts to fix it along with his friends.
 Took it to Andrew on the way back and he fixed it in short order,.. before he took it for a test drive.
  Joe kinda freaked out when Andrew stuck it to the floor,.. Andrew was a bit surprised too

 The exhaust on Joe's "Bummer II" was TT 2.25" with resonator and Borla.
When the car was idleing the vanes were open,.. you couldn't really hear the turbo but it wasn't loud.
 On my 1.5 I have a 2.5" exhaust (that is going on another Rabbit eventually but i didn't have a 2.25" to put on it then) it doesn't have a resonator and was loud with the vanes open.
 So I tied the vanes closed by disconnecting it from the pump lever and strapping the intake lever in the closed position. Now, with the vanes closed I can hear the turbo real well at idle.
 When I step on it I can hear the the turbo climb and can hear it get loud when the vanes are forced closed by the controller.
 Whines higher all the way up, then gets loud/mean.

[fatmobile]

I never had that happen, but was watching for it on the first test drive.
 I think slop might not be the best description of what it needs.
 
 If the boost pivot point can only move as far as the vane control lever;
 it can only push that far.
 As long as the pivot point is close to the vane controller. The father it is from the vane control lever, the less this is true.

 When trying it on the bench, 20 psi was required to push the boost can rod all the way to open.
 So at 12psi the lever isn't even moved all the way.
 I will be watching for the controller to take over the peddle when I tune for higher boost levels.

 A boost controller would work great with this.
 A scrap vacuum switch would allow the vanes to stay closed until the boost hits a preset level,
 then boost would be allowed to push the vanes open.
 The connection to the top of the pump isn't really needed but will help it run more efficiently at idle and through most of the range.

[fatmobile]

I didn't see any criticism in what you said, any more than when you called me and warned me about your concerns ,.. just before my first test drive.
I'm not sure the word "play" even works.
 I hope folks understand what you are saying. It's a concern that needs to be noted.
 When I floor it the rod pulls on the lever,.. pulls it away from the pivot,..
 when the boost climbs, the pivot/boost could begin to push the rod away from it sending the pump into full power until boost drops.
  To do this it would need leverage against the vane controller lever,
 when it's up against it's full open stop.
 
 I didn't get a chance to test drive Joe's 1.6 much and haven't driven it since the boost leak was found. I'm wondering if it still regulates to 12psi without the leak,.. I'm guessing it does. Any increase in boost/fuel would probably back the vanes off. The collar was removed from his max fuel screw so fueling was pretty high already, might be all the way in. I'll have to find another way to add fuel because I don't think it smokes much when maxed,.. kinda busy keeping it under control to look in the rearview,.. did you see any?
 
 I ran my 1.5 without the boost can hooked up and got up over 22psi, without really trying,.. with the vanes tied closed.
 I should have done a test of where the boost is sitting when it's maxed and the vanes are tied open. If I can keep the max boost over that it shouldn't hit the open stop.
  The more boost I want, the farther it runs from the open stop, the shorter distance the  pivot moves, the more closed the vanes will need to be. So adjusting it for higher boost will make it less likely to take over the peddle.

 Not having it connected to the peddle and just tied closed is wasting some energy; trying to keep the turbo spinning at idle,..
 and the moving pivot probably doesn't exercise the vanes enough, might never hit the open postion and clear away the carbon unless I hit the max boost setting, probably not even then,.. but I'm going to keep it that way until I get a quieter exhaust. 
 
I want to put a camera down there and see it in action,.. some day.
 Now it climbs to 12 and drops back down to 11.

[Rabbit on Roids]

If memory serves it was just a slight haze when maxed but it wasn't a long drive and I didn't make a special note of it.

Have you seen this thread?

The EGTs are likely lower now that you eliminated the boost leak.  I've used the VNT-17 on a 1.6TD and with the vanes locked open it would exceed 20 psi without any visible smoke or EGTs going above 1,000°F.

When my vanagon is up and running it should be very easy to make a video of it operating while being driven.

Andrew

if you tie the vanes closed, you are going to blow a head gasket. the vanes make way too much drive pressure when they are closed. mine are 100% open and i can get to 20 psi like andrew, but who knows what my EGT's are, probably pretty low tho (running a VNT and an Intercooler). the only smoke i come up with is from the launch, right before boost builds, then after boost builds and the smoke disappears, usually you lose traction.

[OM617]

Why go to all the trouble of making such a complicated actuator? Just get a normal wastegate actuator.

I would say that if anyone is going to copy the design

Again, why would anyone want to copy such a massively overcomplicated design in the first place? There are far more simple designs out there that work better and don't rely on a mess of linkages.

The vanes don't need to be, and shouldn't, be constantly moving with the throttle position. All you're doing is wearing out the vanes. Every OEM control system keeps the vanes closed until it gets to the needed pressure for the engine load (and/or EGR flow rate).

[rabbitman]

Why go to all the trouble of making such a complicated actuator? Just get a normal wastegate actuator.

I would say that if anyone is going to copy the design

Again, why would anyone want to copy such a massively overcomplicated design in the first place? There are far more simple designs out there that work better and don't rely on a mess of linkages.

The vanes don't need to be, and shouldn't, be constantly moving with the throttle position. All you're doing is wearing out the vanes. Every OEM control system keeps the vanes closed until it gets to the needed pressure for the engine load (and/or EGR flow rate).

Maybe I might want to copy it someday

And do you KNOW that, "every OEM control system keeps the vanes closed until it gets to the needed pressure for the engine load"? Or are you just guessing?

[fatmobile]

Why go to all the trouble of making such a complicated actuator? Just get a normal wastegate actuator.

You have a wonderful way of making simple rods and levers sound complicated.
 Overly complicated?
 A lever on a pivot?
 Damn, you're lazy. I'd hate to see you stewing over how to connect a normal waste gate to the vane controller,.. probably too complicated for you to even explain it.
 ..and you have the just spend money on something else that does the same thing attitude,.. then build a bracket to mount it, and weld up something so it will connect it to the vane controller, then find the right spring so the curve will be right cut the can open to install it (my spring tension is externally adjustable, complicate that), then build something to control that,.. then throw the old part in a box and don't use it.
 Goofy attitude, I just don't understand it. It was already mounted to the turbo, one slotted bracket and a couple washers.
 Doesn't seem like you thought it through.

Again, why would anyone want to copy such a massively overcomplicated design in the first place? There are far more simple designs out there that work better and don't rely on a mess of linkages.

Didn't see any links? and I don't think you can find any that meet the criteria,.. sounds like you are having a bad day and haven't really thought this through.
I am curious if what you say is true,.. about the vanes being held closed until boost gets high enough to need regulated. I have a friend with a TDI and fat exhaust, I could hear his turbo spooling at idle, as if the vanes were closed. I don't know if it was chipped.

 

if you tie the vanes closed, you are going to blow a head gasket. the vanes make way too much drive pressure when they are closed. mine are 100% open and i can get to 20 psi like andrew,

Rabbit on roids, you have a VNT-17 too, just like Andrew right?
 Sounds like it's too much for what I'm doing, the VNT-15 works just right for these lower boost levels.
 Still, a VNT 17 with too much boost is better than a stock turbo. If I ever plan to boost much past 20 PSI I'l have to upgrade.

 Andrew, I hadn't read that post. At first I was thinking you moved the accelerator lever a notch so there would be more on the top end, much like backing out the max RPM stop screw,.. I thought you were looking for more max fuel when floored, but you were targeting the low end so the idle will be lower.
 I keep thinking the 1.5 VNT is going to be tuned for smileage but I might chisel the coller off the max fuel screw and mess with that in the meantime,... because it doesn't have enough power, plenty of air, not enough fuel. I haven't messed with the "outer" bracket on the lever. Since this is a turbo I could probably do the gov mod too. The top is off now (waiting for a new accelerator shaft bushing/o-ring, after it started leaking) so it's a good time.
 On Joes "Bummer II" the max fuel screw was turned in until the spot weld kept it from being turned in any farther,.. it never did get to the point the RPMs wouldn't drop quickly when the accelerator was backed off,.. and idle was under control,.. but I'm not sure how normal the pump was.

[Rabbit on Roids]

I don't believe the vanes are kept shut at idle or cruise on the stock system.  Every credible source I've read has stated that the vanes close only as much as necessary to create the boost pressure for the current demand for power.  Under that criterion, the vanes would be kept fully open at idle and mostly open at cruise, but I have not yet checked firsthand.  I keep asking for someone to post a video of a stock VW VNT system that keeps the vanes closed at idle (with the vanes un-stuck, of course) or cruise.  So far, no one has posted back after the request.  OM617, if the stock vane controls are as you describe, then they would be fitted with wastegate cans from the factory.  The added complication of computer control via vacuum can would offer no benefit and significant added expense.  I don't believe you are correct and welcome you to show that you are by posting a video as stated.  As far as wearing the vanes out, I am not concerned.  Having the vanes stick due to carbon buildup is far more of a problem with the stock setup.  In fact I don't know of any stock turbo failures due to the vanes wearing out.  I have heard of many failing from sticking, tho.  The vanes are free floating and so the only significant pressure against the motion of the vanes will be caused by carbon buildup.  If the vanes are not trying to stick, there will be virtually no wear on them from being moved excessively.  If they do have carbon buildup, then exercising them will help to keep them free.

Fatmobile, I imagine you understand, but if you still have room to adjust the max fuel screw without the idle hanging then there is no need to jump the accelerator lever.    

the vanes are open at idle, and are also open going down the road. when you throttle the engine and it gives it more fuel, it closes the vanes a little to spool the turbo more.

say you are sitting at a stop light, idling - vanes open
then the light turns green and you floor it - vanes snap closed and turbo goes nuts
then the boost builds to its desired limit - vanes open a certain amount to maintain boost

atleast thats how it works on my dads 06 duramax, and it has a big VNT on it with a straight pipe, so you can hear minute changes in vane position.

when the vanes close, they create massive back pressure, and speed up the air entering the turbine, thats why it spools so much faster. if you were to just have the vaines closed all the time, you would be making boost at idle (my car would bring the boost gauge off the needle slightly at idle) and probably 25 psi at cruising speed. back pressure is bad on a diesel, very bad.

so, andrew, im in agreement with you, the vanes only close as much as need be, not closed all the time and open when needed.

[Dougslug]

Here is my take on the simplest way to engineer this
If it were to be set up with a dawes valve the  whole lot would be set up to zero with a full vacumme on,
then when the dawes released it could only go as far as opening the vanes fully

any comments?

[Dougslug]

To clarify a little
I drew two versions, one for a vac actuator and the other for a manifold pressure acutator labeled A and B
Yes you are right, the spring is the only thing closing the vnt, and will affect pedal feel,but is there not also a spring in your linkage?
I cant see anyway to avoid this but I may be misundestanding your post
I would also add that a 2nd cable might be added to facilatate the return of the rods to the open position should you wish to dispense with the
return spring

[Dougslug]

Heres a second take without the return spring

By using the original vacumme can and setting the controll up to be a fully open at full vacumme and controlling boost with a dawes valve
there will only be room for the acuator to opperate when the throttle is open I dont know how this will affect throttle return
I shall have to suck it and see

[fatmobile]

 Great info, good to see some other ideas.
 Yeah, I don't see any reason to have the vanes closed at idle,..
 except it sounds better with the turbo spooling.

[Dougslug]

No simpler, just diffrent
The vanes would be open at idle
reason to use vacume is that it makes use of the spring in the acuator to return the lever rather than pressure from manifold
I hope this will be overcome by the return spring of the IP when the throttle is closing thereby negating the need to accomodate the extra
length of the rod in the cable when max boost has been reached.
Does boost still occur when the throttle is closed?
Dawes valve means that max boost can be set without playing with spring tension, also, if a needle valve were
to be installed in the cab, you could play with the max boost in the cab on the roll.
Hopefully I will build one of these soon and try it on my first m-tdi
Still a box of parts and ideas at the moment though

[blackdogvan]

I like that one Andrew!

[Dougslug]

Dawes valve manual boost control on vacumme acuator

Take throttle to mean accelerator in previos posts, just lazy!