Witch-hunting a boost leak, boost not meeting target

[Tzaks]

Hello,

Thank you for taking the time to read this thread.

I've been beating myself up for the past 3-4 months with a small boost leak.
I'm missing about 1-3 psi of boost under WOT and so far I've replaced/checked the following:

* 1 boost solenoid (only one because I wasn't convinced it would be the solenoid)
* Vacuum lines
* O-rings (chargepipe+fmic)
* Diverter valves
* Checked all connections more than once

No rattle from the turbos. I'm in the process of building a boost leak tester, just waiting on some stuff to arrive and I'll be able to do that.

The strange thing I noticed is that after cleaning one of the solenoids, I had a smaller boost gap between Boost target and actual boost. I cleaned it with some brake cleaner and compressed air.
Example: https://datazap.me/u/tzaks/iulia?log=0&data=3-21

This is the most recent log with 1 new solenoid and 1 old:

datazap.me | Tzaks | After fixing shite

datazap.me

The pull after cleaning the solenoid was much better. TORQUE for the LOG after cleaning the solenoid was: 630 NM whilst yesterday's log was 520-540 NM.

I know that I should be doing a 3rd gear pull for logging but you can see that this issue is persistent.
It would be of tremendous help if people could chime in on this matter.

 

[NoGuru]

Few things first. Do a 3rd gear log. What you have looks like a mess.
How many miles on the car?
Any Modifications to the car?

 

[Tzaks]

This issue is clearly visible at any time during a pull but if you insist, here are some older 3rd gear pulls :https://datazap.me/u/tzaks/3rd-gear-pulls-0?log=0&data=3-21

The current weather conditions in UK are not favourable for 3rd gear pulls.

Car has 140k, running MHD ST2+, FBO minus the inlets.

The latest logs show a slightly bigger gap than the ones I linked to in this post.

 

[NoGuru]

This issue is clearly visible at any time during a pull but if you insist, here are some older 3rd gear pulls :https://datazap.me/u/tzaks/3rd-gear-pulls-0?log=0&data=3-21

The current weather conditions in UK are not favourable for 3rd gear pulls.

Car has 140k, running MHD ST2+, FBO minus the inlets.

The latest logs show a slightly bigger gap than the ones I linked to in this post.

This is much more clear. It looks like maybe the wastegate might not close all the way. Could be the turbos are just worn out. If you have been targeting 18+ for some time that can happen.

 

[Torgus]

At 140k it is VERY likely to be the waste gates unfortunately.

 

[Tzaks]

I understand the logic and I agree that this is indeed very possible.

At the same time I'm trying to explain why in this log there is minimal gap between BT and actual boost but this other log has a huge gap between the two lines. Can the wastegates be intermittent like that?

For testing purposes, would I be able to run both wastegates from 1 single solenoid?

 

[WOT808]

Looks like WGDC reverted to its base value in this other log causing low boost. See this thread for more info.
I suggest:
-Make sure your air filter is clean
-Boost leak test to confirm your charge side can hold at least 20psi (hard to do with stock inlets)
-Confirm that your WGs are fully closed at ~6" hg and are receiving/holding sufficient vac as seen here

 

[Tzaks]

Thank you. I will start testing this weekend. I'm using DCI and they are quite new so I don't think the air filter would be the culprit.

I'll update as soon as I have some results, hopefully I'll get to the bottom of it.

 

[RSL]

I understand the logic and I agree that this is indeed very possible.

At the same time I'm trying to explain why in this log there is minimal gap between BT and actual boost but this other log has a huge gap between the two lines. Can the wastegates be intermittent like that?

For testing purposes, would I be able to run both wastegates from 1 single solenoid?

First one is INA0S and PID works, second one is IJE0S and PID does nothing. PID is the dynamic part of control used to trim WGDC against actual/target error. Without it, there's no dynamic control and only runs base+temp WGDC regardless of error to target. First WGDC final is up to about 63% with the PID add, second is only up to about 53% without it.

 

[iminhell1]

Vacuum est the wastegate actuators.

For my car, the front held but the rear leaked. I'd occasionally make target but most times i wouldn't. Boost was not regulated well and the car was really moody. sometimes go like stink and others seemed to layover. I set target high so I'd make good boost even when not working right. But when it did work it was waay too much boost.

Odds are it'll be the rear actuator, not fun to replace.

 

[Tzaks]

Update:
I found the issue yesterday when I was installing inlets. One of the diverter valve hoses (the plastic ones) had small holes on the accordion part. I noticed it when I was converting the end to fit the silicone inlets. PTFE + electric tape fixed it and now it's boosting happy, hitting target constantly and holding to red line.

Moral of the story:
Even though my car has 141k miles and I was ready to accept defeat thinking that the turbo's are old and tired I kept trying and kept investigating. I should mention that my car is on stock turbo's and from what I saw yesterday when I was installing the inlets, the wastegate flap hasn't been upgraded. In all fairness, I'm not sure if the previous owner has replaced the turbos. Car was stock until 133k.

Thanks again for all the people that chimed in and offered advice. It was a small push but this made me buy inlets and find the leak

datazap.me | Tzaks | New inlets

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