Newly Installed Downpipe, Worsened Boost Flutter/Fluctuation

[DSMtuned]

https://youtu.be/pw7i13hSIL0

Hello,

I just installed my catted downpipe. This boost flutter happens at moderate throttle, low RPMs, and with moderate load. It happens with the stock calibration, my last revision custom tune, and with the updated custom tune to correct for the downpipe. Atached is a a log. You can see it happens 3x a second.

Screenshot (29).png

I noticed this with the stock calibration prior to the downpipe when locked in 6th gear going 65 in the mountains, but to a lesser extent. It happened occasionally with my custom tunes, but never this dramatic and only when really lugging. Now it occurs with all of my prior custom tunes and with the updated ones.

It sounds like the BOVs are dumping boost. If you look at the logs, the throttle angle and the wastegate increase just after the boost deceases, mostly.

Here are my working theories:
1) BOV solenoids (one or both) are failing. 2012 here, so mechanical BOVs.
2) Wastegate solenoid is failing. You can see the WG percentage sometimes falls when the boost falls, but not always, so I'm thinking the sharp increase is more of a compensation.
3) Wastegates are mechanically being blown open due to weak springs and the decreased backpressure with the new high flow downpipe made this worse.

Not too long ago I cleaned my MAP sensors and placed clamps on all my vacuum hoses. I also checked for any cracked lines or connections.

Any ideas here? I want to be excited about my new downpipe, but I'm really feeling kind of bummed.

[zfgracing]

What is the throttle body doing? do you have and HPT log.

Off the cuff I would say it's mostly likely a bad tune from a combination of bad practices tune wise but with out seeing any real hard data it is hard to tell. post a log of the event, the stock tune and the current tune.

[DSMtuned]

So the problem is that I don't have an HPTuners log. I found this forum when looking for more information on doing my own tuning. Unfortunately at this point I'm tied to one of the reputable email tuners. They are looking into the problem, but it's almost been a week now with very little response from them.

Here's a log of TIP desired vs TIP actual. The second log is throttle angle actual vs boost.

Today I replaced the wastegate solenoid as a rule-out and this is what the wastegates continue to do: https://youtu.be/xDEsR0Yk3OQ

ffile:///C:/Users/Craig/Pictures/Screenshots/Screenshot%20(30).pngScreenshot (30).pngScreenshot (31).png

I've tuned my own cars for years and feel helpless relying on someone else to tune this thing for me. Any ideas what might be going on here?


I appreciate it.

[murfie]

Post the .csv file. its better than screen shots of live link.

[DSMtuned]

Post the .csv file. its better than screen shots of live link.

Below is the .csv file. I replaced the wastegate solenoid yesterday as a rule-out and nothing changed. I also checked the BOVs and they have no tears and appear to be working correctly. All intercooler hoses have been tightened and the vacuum hoses were all checked.

Boost fluctuations 91-2.csv

The truck is doing this on all previous tunes as well as the updated tunes for the downpipe. I'm so frustrated at this point. I'm towing my camper across Colorado soon and need to figure this out. I'm almost at the point of just buying a new stock downpipe and installing that. The truck ran so strong like that.

Any ideas on what else to check?


Thank you.

[murfie]

Your TIP pressure is above your desired TIP pressure. This is opening/closing your throttle to limit boost and giving you a fluctuation. Your engine is making more TQ than you are commanding. Add to your DD table in the problem area or increase effective area for that predicted throttle angle vs ECT vaccum small amounts making sure you do not increase above any value in the next higher predicted angle. If you approach the next up columns values that column needs to be increased also. Keep both predicted throttle angle and effective area tables in the same relationship to avoid limp mode.

[DSMtuned]

Your TIP pressure is above your desired TIP pressure. This is opening/closing your throttle to limit boost and giving you a fluctuation. Your engine is making more TQ than you are commanding. Add to your DD table in the problem area or increase effective area for that predicted throttle angle vs ECT vaccum small amounts making sure you do not increase above any value in the next higher predicted angle. If you approach the next up columns values that column needs to be increased also. Keep both predicted throttle angle and effective area tables in the same relationship to avoid limp mode.

Great info! Thank you very much!

[DSMtuned]

UPDATE-- **FIXED**

AJP turbo was kind enough to build a test tune for me so I could rule out my tuner's calibration as an issue. After loading his tune, I found the boost oscillation persisted. This led me to believe the problem was mechanical.

I had a feeling that the catch can check valves could be an issue because they are simple spring loaded flaps of rubber vs ball valves. I took the check valves apart and found both to had failed, causing boost leaks!

Next I built a boost leak tester. I found a slit in the driver's side wastegate line under the clamp, where I missed it during inspection of the lines. After fixing this and returning the PVC system to stock until I can get new check valves for the catch can, I took the truck out for a spin.

FIXED!!!! Unbelievable! I think it was coincidence that the boost fluctuation coincided with the downpipe install, or I worsened the wastegate line leak during the install.

So I learned to not forget my roots of tuning DSMs and Subarus and go for a boost leak test right away instead of going down the road of more complicated problems.


Thank you all for brainstorming with me. It's great to have a community like this to learn from.