VNT Actuator Adjustment - GTB Turbo on an '06 BRM

[fwthompson]

vnt adjustment.

I have a almost stock 06 jetta brm, its running stage 1.5 malone. My question is what could be the possible problem for my setup. I have the actuator lenght setup close to what seems perfect but im still getting a check engine light from the smart sensor. The actuator is a replacement one from idparts. I have checked all the connectors and cleaned them. I set it up when it was good and hot and ran the 011 menu on it several times. Could a new sensor be bad or are these the wrong smart sensors for the car? Thanks for all the help so far. These fourms have helped me so much with this car.

 

[nin2]

Hi, everyone, I have pretty similar setup - gtb1752v turbo fitted to 1.9tdi PD105 engine and pretty mild remap. I also have 3 bar map sensor, but stock clutch. Problem is that car feels underpowered until around 2200 rpms. I made group 11 log WOT in 3r gear and now its pretty obvious why - actual boost pressure lags behind specified, when actual catches specified, car starts to drive much better.
here's 011 graph:

here are group 01, 08 and 011 logs:

So the question is - what should I do to cure this? Do I have to shorten actuator arm or maybe this can be sorted out by my tuner?
Any help appreciated.
Thanks.

 

[DanG144]

I would start by checking out my vacuum system. You should have 25" hg or more vacuum at idle.

It is pretty easy to do this with a vacuum gauge while performing BASIC SETTINGS test 011, Charge air control.

Verify what the vacuum supplied to your N75 is, what the vacuum out of the N75 does during the test (it should go from 20" or more to less than 5"). Watch your vacuum actuator on the turbo during this test. It should move about 11mm or more.

I think you will find your problem doing this fairly readily.

 

[faboka]

Duty cycle looks ok to me on that log.

Log group 11 under basic settings. RPM increases to 1400 rpm and cycles from actuator ON to actuator OFF. Whats the difference in pressure between the two?

 

[nin2]

I didn't have chance to get under the car and measure supplied vacuum yet (I'll try to do that later this week), but I did measure group 011 basic settings and output tests.
basic settings (difference is 1104 - 984 = 120 mbar)

output tests (difference is 1020 - 996 = 24 mbar):

 

[duke21]

Please help: to get more boost (actual is lower than specified) on push type actuator, i need to shorten rod?

 

[DanG144]

I usually measure the vacuum at the N75, which is easier on the US models, than some European models which use a block or manifold for the vacuum connections.

Based on your readings, I suspect your vacuum system is healthy.

Have you done an initial setup of the actuator? Set it to start moving at 3 to 5 inches of mercury vacuum. Ensure it is at full stroke by 18".

Since your response is slow, setting the rod length to start motion at 3" (lower end of the band) will give you higher boost.

I think this is a longer rod, for a push type actuator; but I am sure you want more motion with less vacuum.

 

[nin2]

Thanks for advise!
I finally manged to do measurements, well - almost all of them.

Actuator seems to be set up properly, it starts movement at 3 and hits stop screw at 18
I couldn't measure vacuum supplied to N75, because unfortunately I have one of those "european models" with vacuum solenoid block instead of normal N75

But Basic settings test showed that vacuum supplied to actuator was between ~4 and 24 InHg

 

[DanG144]

The start of motion may need to be set above 4, then. Otherwise your turbo will never get to the minimum efficiency internal stop. If your positioner allows (if you don't get a positioner trouble code), I would set the turbo to start motion at 5 inches Hg. That would probably put the high vacuum stop at 21"hg or so. This would tend to center your operation in the band, which normally gives the best response. It would tend to lower your boost very slightly.

However, if you are not overboosting, if your actual boost is close enough to specified for you, then it is probably not necessary to adjust anything.

 

[Mack]

Para mi vas con un mapa de gasoil muy pobre para mover un 1752.
Debería inyectar mas desde las 1600rpm para mejorar la carga del turbo.

 

[DanG144]

Para mi vas con un mapa de gasoil muy pobre para mover un 1752.
Debería inyectar mas desde las 1600rpm para mejorar la carga del turbo.

(poor translation)
For me you are on a map of very poor to move a 1752 diesel .
It should inject more from 1600rpm to improve turbo charging .

 

[nin2]

Thanks for the advice!

I have unerboost issue so I think lengthening actuator would only make things worse. Besides I'm not sure if I can 100% trust my cheap chinese vacuum gauge

I actually hope that this issue could be related to ecu and not actuator or stop screw...
My current ecu map was made with intention to save clutch, therefore IQ at low revs is pretty low now. To be honest I'm also not sure if my tuner understood me correct when I told what exact turbo I have now, so it's possible that he didn't take in account, that its quite a bit larger than it was before.

Anyways - yesterday I did clutch upgrade to SMF/VR6 so I think I'll leave actuator alone for now and talk to my tuner about retune

 

[poisas]

Hi, i"m now into adjusting gtb17 turbo with vaccum actuator from vnt20, i still dony get it, how do you adjust that it starts moving on 4inhg? You need to make it so long so there is totaly no boost making at all, i set stop screw to almost full close, and i need to shorten rod a lot to get some boost, else if i make pull type actuator move at 4inch then it has to be tuned with some force at full open positinion, it hits stop point at the internal vnt mechanism, and aply some force to it. Then it only moves at 4 or 7 inch depends how much i lenghten it a force is aplyed to full open position. Im afraid, that internal full open stop spike wont hold it, ant vnt vanes wil hit the blades, is this how you make actuator move 4 inch of mercury? It has to be forced into full open position? And also how i would have to setup it to give car to the tunner ? Turbo is gtb1756vk vacummconversion with vnt17 leg, actuator from vnt20. Ecu has a stock remap made with stock engine.

 

[nin2]

And also how i would have to setup it to give car to the tunner ?

I would also like to know that
p.s. I have a feeling that these 3-5/18 HgIn initial actuator settings does not work with hybrid or bigger turbos.

 

[poisas]

Actualy i have spoken with a tunner that has 100+custom tdi's done, and he gave a mechanic number, that acorrding tuner is making hybrid turbos, and his vacuum actuator and stop screw adjustments are perfect, i have spoken with the guy, and he told me just make so that on gtb17 turbo lever would hit stop screw at 17" and dont wory about how it starts to move. Nin2 i have exectly same "issue" if its issue, cause my ecu has remap that was designed for 81kw >~100kw on stock engine with vnt15 turbo. And i have did several logs, you can try also log the 3 8 and 11 chanels, to see how the MAF behaves, cause i see that there is not enough Maf, boost, and fuel injected according specified. up to ~2200rpm then it becomes "alive" it was same how much stop screw adjusted, and how shorten the vnt leg was, what i could make, that i could have some 1.5bar pressure, and power after 2200rpm but still it was slugish at low rpm. What i believe, its because remap. It has to be gtb17 map, then we can see what happens. I have borrowed vacuum tester, have set turbo to touch stop screw at 17" tested n75, it gave 18". used paper to see if it touches. And i have set stop screw 1 full turn from fully closed. its not spiking boost at all now, and woot on 3rd i get 69%duty at 4000rpm. so thats fine for a tunner to start. I also thought maybe the maf sensor is getting bad, but cannot find a reason why it should become bad, as before turbo it was ok. i test the realy bad maf i had, car was undrivable so i have put back my oem bosch maf.

 

[duke21]

Can anyone explain this. BMN has push style act. I have problem with throttle reaction it feels sluggish. When i disconnect vnt connector car is totaly different - great response. Turbo is 2260 vk and 4bar map. But boost is climbing rapidly and no limit, im in fear to push wot because i get up to 2.5 bar in 2nd gear but cant hear surge...

 

[A5INKY]

Can anyone explain this. BMN has push style act. I have problem with throttle reaction it feels sluggish. When i disconnect vnt connector car is totaly different - great response. Turbo is 2260 vk and 4bar map. But boost is climbing rapidly and no limit, im in fear to push wot because i get up to 2.5 bar in 2nd gear but cant hear surge...

Sounds to me like you have a push style actuator mounted with a pull style bracket. TDI VNT turbo vacuum actuators have return springs that should pull the VNT open (away from the stop screw) when vacuum is removed. This design creates a fail safe. Vacuum should pull the VNT into maximum exhaust energy directed at the turbine wheel, or in other words, on the stop.

Your description sounds like the bracket is reversed.

 

[duke21]

Please can you explain difference between push and pull style bracket? I didnt noticed that.

 

[A5INKY]

Please can you explain difference between push and pull style bracket? I didnt noticed that.

The bracket design depends on the type actuator you use. No matter what, when there is no vacuum to the actuator, the actuator return spring should be holding the VNT arm completely away from the stop screw. Therefore, when vacuum is applied it will pull the VNT arm down against the stop. This is how all vacuum controlled TDI VNT turbos are set up regardless or push or pull style actuators.

It sounds like you have yours mounted opposite to where the internal actuator return spring pushes the VNT arm against the stop screw when there is no vacuum. If I am right, you must either change to a pull style actuator with your current mounting, or make a new bracket to move your push style actuator 180 degrees out from where it is mounted now.

 

[duke21]

But my actuator is mounted on top position as default on this engine. My question is why is car behaving so much better when vnt connector is off. If actuator is positioned on top i think it has proper bracket...

 

[poisas]

Thats the question, how the lever arm is when engines is off? Is it on stopscrew or oposite?

 

[duke21]

oposite, it goes to stopscrew when engine is started. But it seems that it goes too slow, so reaction on throttle is laggy. But when disconnected its ok. Maybe position sensor is wrong? Vacuum is measured and ok, actuator is starting at 3inhg.

 

[DanG144]

So it behaves much better with the electrical connector off? With vacuum still hooked to it?

Some of the early actuators sold here had reversed position feedback sensors on them. It reported 0 when it should have been reporting 100%, and vice versa.

Have you checked the position feedback with VCDS? On many PD cars you can look at position 2 of measuring value block 43 to see what the reported position is.

With the position circuit disconnected it would fall back to a simple demand operation (ignoring the absent position), similar to the older VE engined cars.

 

[duke21]

Yes vacuum is still on of course I looked at vcds and was reporting 85% up to 2600rpm, then falling. But there is no limit so with 70% thr today boost jumped to 2.7 bar!!. In map is requested 2.1. Im afraid to try wot - can i destroy turbo this way?

 

[DanG144]

Just to be clear, were you looking at the position in mvb 43-2?

Check the position with the car off. Zero vacuum to the actuator. It should read -7 to less than 20%. Pump it up to 20 inches of mercury, it should read between 80 to 120% position.

You can also do basic settings test for charge control, some of them report position, some do not. This should cycle from min to max. Take a screen shot at max and min...or post a picture of a graph...

Yes, you can damage your engine or your turbo, so do not push too hard.

 

[duke21]

its reporting difference of only ~30mbar. what should i do?

 

[A5INKY]

oposite, it goes to stopscrew when engine is started. But it seems that it goes too slow, so reaction on throttle is laggy. But when disconnected its ok. Maybe position sensor is wrong? Vacuum is measured and ok, actuator is starting at 3inhg.

This is what it should be doing, meaning my concern was unfounded and your bracket and actuator seem to be properly matched. It does sound like your VNT is in need of some basic mechanical set-up though:

its reporting difference of only ~30mbar. what should i do?

That is not enough difference. The VNT geometry at the stop could be improved to get the turbine spinning and help build boost off the bottom. Need to shorten the stop screw to increase that difference to minimum of 80mbar. I find 100-120mbar perfect for my set-up. Once the stop screw is right you can tune the rod length.

 

[duke21]

Thanks A5INKY! So first sscrew to get 80+, then length?

 

[A5INKY]

Yes. Stop screw adjustment first, then rod length.

I would shoot for 100-120mbar difference, but don't go above 150mbar. That is a fairly wide target to shoot for, but it can be a very sensitive adjustment. Make small changes and retest until it is right.

 

[duke21]

Ok, how to adjust rod length. I read many topics here. I need to lengthen rod to get faster reaction right?