Overboosting ALH

2001 jetta automatic
DLC 520
GT1749VB
Stock map sensor
Egr delete
Straight pipe exhaust
Stock intercooler
Malone eco tune
Forced economy mode with transmission - 00011 coded in
Recent engine rebuild, stock compression just upgraded rings and bearings

Fault code p0234 for overboosting
No vacuum leaks
Vacuum is pulling 30+ inhg
Set actuator to start moving around 3inhg
Hits stop screw around 24inhg

The turbo was a used unit that worked, I drove the guys car for a few days years ago with no issues. He upgraded shortly after and sold old turbo to me. It sat in my storage bin until needed. I adjusted the actuator because they were all out of spec. First road test with this turbo shows boost building quick under medium load, say 60%+ according to my scan guage. 1st, 2nd, are all ok and I won’t over boost.

Returned to my shop and feed vacuum manually with mityvac and watched the rod and actuator for skipping, found none, left vacuum applied for a lunchbreak and came back to no drop.

2nd road test No change but a few notes

This is the important part:

Problem occurred after GT1749VB was installed
GT1749VB was missing stop screw and the rod length was tamperd with
1st gear all ok
2nd gear all ok
3rd gear TCC unlocked is ok but very close 18psi
3rd gear TCC locked rolling on the throttle I over boost to 23+ and limp mode
4th gear TCC locked is the same as 3rd locked

The delima:

If everything was stock I assume the turbo is faulty or N75 controller, so I put a new n75 in anyway because it’s cheap. Same issue persists. Did I miss something on my inspection, did I misadjust the actuator on the turbo for a GT1749VB, is it my tune?

I need to understand this.

Screenshots before logging started:
Cold Idle

Hot Idle

Ready Status

DME/ECU

DME/ECU Faults

TCM

TCM Faults

3rd gear locked TCC
[url=http://pics.tdiclub.com/showphoto.php?photo=133144&title=p0234-graph&cat=7134][/URL]

your tune isn't appropriate for your modifications, it's designed for a stock turbo and stock injectors. Probably overfueling since you've gone from a .158 to a 205 nozzle size. Can treat a vnt17 like a vnt15 tune wise but it's not ideal, hammer modding your IQ up to 8-9 will temporarily reduce fueling a bit and may give some improvement.

I'd start with vcds data logging block 11 to see exactly what the turbo is doing. Reduce fueling and see if that helps.

Owain@malonetuning said:

your tune isn't appropriate for your modifications, it's designed for a stock turbo and stock injectors.

I agree but this was discussed before purchase and a list of modifications were provided

Probably over fueling since you've gone from a .158 to a 205 nozzle size. Can treat a vnt17 like a vnt15 tune wise but it's not ideal

seems that way, it works for 80% of my power band but likes to get into limp mode near the top end, say around 3krpm. I do have a set of stock injectors that could be installed later on.


hammer modding your IQ up to 8-9 will temporarily reduce fueling a bit and may give some improvement.

I need to research this again, I forgot about hammer modding

I'd start with vcds data logging block 11 to see exactly what the turbo is doing. Reduce fueling and see if that helps.

Log and screen shots provided

Click to expand...

Since my last post a correction was made:

The stop screw on my turbo was set at 24inhg this is now set to 18inhg

All logs and screen shots are current now

Results are boost actual vs specified are more inline when driving around town and getting on the freeway. MAF readings are better. The boost dumping between gear changes is now gone. Engine is quite and sounds more like a common rail TDI under load. Idle still sounds like a Kubota but that's expected with injectors and the injection system.

Logged into VCDS and Moved the IQ setting Via coding, vehicle is very lethargic around town and boost is slow to build, no limp mode or p0234 when floored in 3rd gear with TCC locked.

Before:



After:

you can drag/drop logs onto our site to plot them and copy/paste links here. The N75 is maxed out and unable to control boost. Fueling needs to be reduced if it's smoking or the actuator needs adjustment.

https://log.malonetuning.com/chart/272436

https://malonetuning.com/assets/uploads/2627c0efe8d92215712933f942839993.png



blue is what the ECU is requesting, red is what the turbo is doing. It needs mechanical repair and tuning appropriate for the hardware wouldn't hurt either.

I am so much better numerical logs than graphic logs, but here goes... I will guess the % is the N75? The N75 valve on an ALH works what you would think is opposite to logic: a high N75% means the N75 is trying to bleed off the boost, but it doesn't seem to be working in your case. If it were me, I would lengthen the actuator rod on the turbo a turn or two at a time, until the spike settles down. M-K you say the stop screw wasn't there and then you mention the original actuator set to 24 PSI. If there is not stop screw at all, I would get one in there ASAP! If there is no stop screw the turbo will at some time, go full boost and stay there until the turbo twists itself apart.

Nevada_TDI said:

I am so much better numerical logs than graphic logs, but here goes... I will guess the % is the N75?
yes it is!

The N75 valve on an ALH works what you would think is opposite to logic: a high N75% means the N75 is trying to bleed off the boost, but it doesn't seem to be working in your case.
i agree

If it were me, I would lengthen the actuator rod on the turbo a turn or two at a time, until the spike settles down.
ive done this 3 times at 2complete turns a piece, it’s now not building boost under light throttle and that is what I wanted, my issue is now completely under heavy load and passing
So overall it’s an improvement that i’m happy with for now, i’ve got a set of stock injectors i’ll Be installing with before and after graphs for everyone! Fully convinced my issue is only over fueling at this point, I believe with the other injectors installed i’ll Now for sure.

M-K you say the stop screw wasn't there and then you mention the original actuator set to 24 PSI.
ohh no no no, I should clarified that bit sorry.

The turbo had no set screw and the actuator rod was extremely short when I got it, compared to my removed VNT15 I knew it was going to be a issue. So I followed member Dang144 post on vacuum measurements and setting up the turbo actuator. You know 3-5in is starts moving final position should be “x” based on “y” measurement of vacuum during short test of the n75.
The stop screw was removed from my VNT15 and installed on the GT1749VB, vacuum was applied to 24in then the stop screw was run up and touching the VNT arm. Then backed off to spec with a feeler gauge. Then I moved the stop screw to 18in and set the spec again with the feeler gauge. This is now its final position for the next 2 logs i’ll Post.

If there is no stop screw at all, I would get one in there ASAP!
done, it was the 2nd or 3rd item before installation

If there is no stop screw the turbo will at some time, go full boost and stay there until the turbo twists itself apart.
lets avoid that

Click to expand...

I’ll send you the data logs in a email

If you scroll down on the log viewer it has the raw data too

Final graph with DLC520 installed
[url=http://pics.tdiclub.com/showphoto.php?photo=133160&title=1-p0234-graph-final-with-dlc520&cat=7134][/URL]

Changed out the injectors and road tested, this is what I got
[url=http://pics.tdiclub.com/showphoto.php?photo=133161&title=1-p0234-graph-final-with-stock-injectors&cat=7134][/URL]

Day 2 and another trip over the mountains with no overboost, think i’ll call it a fix at this point and around 250 miles. Thank you Owian sand NevadaTDI!

Can my original combination be salvaged? And what tune should be installed?

Glad to hear it's running well

Yes you'll just need to update the tune for that hardware, can install a 3 bar map sensor at the same time too (will need a tune set for that) to help diagnose any higher boost values down the road. This turbos good for 24-26 psi and you should have fueling for a clean ~22 with the IQ set around 3-5.