Weird VNT actuator setting?

[dieselpower04]

So I'm trying to figure out what's up with my car. Its been over-boosting for a couple months now (could actually been doing it entire time I had the turbo).

Background of car: 128k miles; enough mods and $$ to put down 182 whp on a Dynodynamics dyno (usually 10% lower than a Dynojet).

Turbo: VNT-17/22 (IDParts, approx. 60k miles on it)

Tune: RC4+

Problem: going up a small hill, 3rd gear, pushing 10 psi with very little throttle input?!
Pulled vacuum line off N75 and used mityvac to check actuator movement. It starts to move @ 5 inHg but reaches full movement (doesn't move anymore) @ 15 inHg or less?!

Replaced the line from turbo to N75 with new line. Removed intake flapper and EGR valves; both the lines that went to them now go to N75.

How is this possible?

 

[85_305]

Dude I'm in the same f*cking predicament with my car. I'm assuming the motor isn't sooted up as i get the feeling you use it. Your vnt actuayor might be sticking. Use some wd40 or pb blaster and just coat the vnt mechanism and harp it for a few miles. If it stop overboosting, problem solved. Dry the vnt off real good and apply a disappearing lubricant to it. Otherwise try screwing your vnt nut in 1-2 complete turns. Report back! Also, with the level of mods you. Have, consider a boost valve or mbc to help control boost. Works like a charm for me 98% of the time

 

[dieselpower04]

Dude I'm in the same f*cking predicament with my car. I'm assuming the motor isn't sooted up as i get the feeling you use it. Your vnt actuayor might be sticking. Use some wd40 or pb blaster and just coat the vnt mechanism and harp it for a few miles. If it stop overboosting, problem solved. Dry the vnt off real good and apply a disappearing lubricant to it. Otherwise try screwing your vnt nut in 1-2 complete turns. Report back! Also, with the level of mods you. Have, consider a boost valve or mbc to help control boost. Works like a charm for me 98% of the time

I want to try and adjust the actuator, I just don't see how I can do it on the car. There is so much stuff in the way. I don't have the luxury of a garage any more so I have to do it in the parking lot of my apartment complex.

And with the boost valve, I had one in, and took it out. At full the throttle the car runs like a champ! 26.5 psi full boost (28 psi spikes). Its the less than 25% throttle part that is giving me trouble.

 

[85_305]

perhaps your n75 as well. But do you have the stock intake manifold and egr? If so, good luck getting to the VNT rod unless you go from beneath.

 

[dieselpower04]

I have a PD150 intake manifold. One night the EGR was stolen off my car; don't know who did it

 

[85_305]

Your egr was stolen? What the ****? Well thanks to them, I suppose.

If you have a pd150 then you can get to the VNT rod thru the pass side fairly easily. Just grab a wrench and stick it on.

 

[dieselpower04]

Your egr was stolen? What the ****? Well thanks to them, I suppose.



If you have a pd150 then you can get to the VNT rod thru the pass side fairly easily. Just grab a wrench and stick it on.

I guess I will try and take off my intake pipe from the intake manifold to get more room at it. So you are saying from the top, passenger side? Not thru the wheel well right?

 

[85_305]

If you have a pd150 intake that exits towards the drivers side, and you have no egr, you should have a TON of room from the engine bay. I've swapped out complete turbos going thru the top of my car (although its MUCH easier going thru the bottom also..).

you shouldn't need to take any pipe off though.. unless your IM exits to the pass side??

 

[dieselpower04]

My manifold faces the passenger side. Its just like the stock BEW, without all the EGR and intake flaps.

 

[85_305]

Ohhhh. I have a passat manifold, which leaves the whole pass side wiiiiiiide open, and the IC hookups face the the drivers side. I would unbolt the pipe then like you said and try to get to it. It's literally one little bolt to turn, so you dont need a ton of room. If it's easier, jack the car up and go from the bottom.

 

[dieselpower04]

Ok cool I will try. I think I will lengthen it and test with mityvac.

Hopefully I don't need a new actuator. The 'smart' ones are $120+

 

[Farfromovin]

After reading about your issues Chris, I'm leaning towards you might just have a little chunkiness in your VNT that prevents it from initial movement, hence a little overboost. How does the lever feel when moved? Is it smooth travel? The best thing to do is remove the little C clip and just wiggle the arm on the turbo back and forth. Be forewarned though, that little clip likes to fly away when you remove it! Some boost logs of normal cruising would be good too! If the duty cycle is really high during this "condition", then you do have a mechanical issue. On the flipside, if the duty cycle is pretty low then your tune is just really sensitive to inputs. I've had an RC tune or two that are really happy to get the boost going quickly. That's kinda Jeff's style with his higher level tunes.
Bottom line- you need vag logs to determine if it's a problem or not. I'd recommend forwarding your logs to your tuner. Keep us posted with what he says!

 

[dieselpower04]

Phil, I can't move the rod by hand (not sure if I should be able?). If I squeezed the mityvac past 15 inHg (were it initially stops), it would most just a little little more (fraction of an inch) and was not smooth.

I will try removing the C-clip to check the interval vane movement. I just wish it was a little easier to get at!!

I will try and get some logs on Wednesday, which is when my local VW people meet up

 

[85_305]

DONT LOSE THE C CLIP!!!!!!

But 15inhg is a bit low... def crank the nut down 1-2x. I'm willing to bet you just need to lube up the rod some.

 

[DanG144]

I am having trouble understanding what the issue is. I have the "medicine head" from sinus medicine right now, so I am not running at full boost myself.

Let's see if I have this right, it is not overboosting at full throttle or high power situations?
But you do not like that it is boosting 10 psi going up a small hill?
Am I missing something?

I think it is normal to boost 10 psi going up a small hill on a tuned car. It is getting boost and airflow up so that you can get plenty of fuel if you put your foot in it.

On the rolling hills around here (midlands SC) , I routinely go from 0 boost downhill to 12 - 16 psig going uphill. In Florida (flat as a fritter) I will see 5 or 6 pounds of boost going up an overpass on the interstate.

While you would rather see a larger range on your actuator, I am not sure you can do much about it. If you lower the number where it starts moving, you will also lower the number where it is at full stroke.

If my car was running where yours is, I would leave it alone unless it was truly overboosting. If I did anything, I might move the initial break point up to 7" or so, expecting to see full travel also increase by 2" to about 17". This would perhaps help minimize spikes and overboosting.

 

[jcrews]

The 17/22 would have been bench calibrated at the factory. What does the MAP request/actual indicate (use VCDS)? Remember, futzing with the actuator will void the warranty on the turbo.

I'm asking the same question as Dan. What led you to conclude the manifold pressure is incorrect?

 

[dieselpower04]

Dan you are correct in my feelings; doesn't overboost in full throttle situations. The actuator stops moving (comes to bottom) @ 15 inHg with the mityvac, which is definitely before it should.

This is apparent sometimes on the highway; cruising @ 70 mph and pushing 7-9 psi (makes even my FMIC hot in FL summer).

I will be taking logs tomorrow night to see what I can from that.

About the warranty: I don't think it applies anymore, 60k on it

 

[DanG144]

Like jcrews, I would be interested in the logs.

Good luck.

 

[suffeks]

my vnt17/22 didnt seem to come calibrated, i will soon be checking using a vac, i played a bunch with the rod by trial and error...

for 99% this is what happened on my car:

in 2nd gear boosted fine and early, 3rd and up it was slow to spool, typically could get max boost over 2500rpm and closer to 3000rpm

this is what happened after driving for 1000km...

it now seems to boost too easily, i am talking like 10-12psi in low gears with very very very little gas, previously it was 2-4max. so i am not sure what is up, the turbo is maybe a few months old too.

during the premature boosting, if i floor it, sometimes it goes back to the old routine for a while. anyway i will be checking that actuator properly.

 

[85_305]

If the car is boosting too easily, suffeks, I would recommend making sure the vnt isn't sticking. Thats how I know my rod is stuck; the car boosts WAY too easily.

 

[suffeks]

it started boosting way too easily after a 1000km drive, but it's happened before, i would say it happens very rarely. otherwise it boosts slow in higher gears. so i need to adjust the rod to be in the middle somewhere. but why it does 2 different ways i have no idea something definitely wrong... i will start by checking with a vac

 

[85_305]

I would just romp on the car for a few miles.. if you were travelling and kept throttle/rpms/boost low, you prolly just sooted up the motor/turbo. Just romp on it and it should clear up in a few miles.

 

[suffeks]

haha more like i was doing 24psi all the way lol victoria to calgary, going up some really big hills too!

 

[dieselpower04]

I don't really think my problems are from sooting up. I beat the living sh$t out of my car. 26 psi at least once every time I get into it!!

 

[dieselpower04]

Logs here!

Here are some logs from last night:

The first one is the whole thing, then the following graphs are segments of the whole set.

You can see when I am into the throttle, they match nicely.

When I'm driving regular, they don't match well at all.

What should I do to fix this?

 

[oldpoopie]

I know you said that the lever starts to move at 5, but are you sure its at its max extention when you start or is it hung up on some soot etc?

 

[dieselpower04]

I know you said that the lever starts to move at 5, but are you sure its at its max extention when you start or is it hung up on some soot etc?

I think so. I can't move it any farther with my fingers then where it starts from

 

[Joshua]

**Disclaimer** The pressure side of your chart is off, but that's because I didn't add the atmospheric measurement in before we started.

Another note, if we were looking at the right block, the duty cycle on the N75 was typically around 80% during normal driving. It was kind of hard to see the screen when he floored it ( ) but it appeared to drop to about 30% at WOT.

 

[dieselpower04]

I corrected for the atmospheric contribution. At idle it was reading apprx. 1030 mbar, so I subtracted that out to get actual boost pressure.

 

[dieselpower04]

I will add the graphs with the N75 duty cycle shortly!