AirC unstable when above 20psi boost

[pedal_r]

The airC on my datalogs keep fluctuating after it gets past 20psi. My tuner tells me its a possible boost leak. I've done a smoke test and also pressurized test from the the inlet pipe all the way through the engine. I didn't find any leaks. There's no trouble building or holding boost pressure. I've also cleaned the MAF sensor twice with MAF sensor cleaner. My next step will be getting a brand new MAF sensor. My tuner tells me that he can't continue tuning until I get this issue fixed.

I was previously running a drop-in turbo before the G25 kit, with all the same mods. I reviewed the logs from the old setup and there was no AirC issue with the drop-in turbo. Although I performed multiple leak tests and everything was good.

Datalog attached

Mods:
Rampage Gen2 G25-660 kit
4in MAF housing (also tried using PRL race MAF with same result)
XDI HPFP
Modded HPFL
DW300 LPFP
PerformNC 1400cc injectors
PRL flex fuel sensor V3
PRL HVI
Turbosmart BOV (recirculating)
Mishimoto intercooler w/ piping
PCV and CCV catch cans

[Spunkster]

This could be because your fuel duty cycle is fluctuating a lot.

[jeffx]

note that it appears to be overshooting the DIFP target by a fair margin and this could be causing the fuel duty cycle oscillations that I am also seeing (reported in this thread).

Another thing I'm seeing in the log - the aircharge fluctuations also begin when the wastegate cracks open.

[pedal_r]

This could be because your fuel duty cycle is fluctuating a lot.

Any idea what the cause could be?

[pedal_r]

note that it appears to be overshooting the DIFP target by a fair margin and this could be causing the fuel duty cycle oscillations that I am also seeing (reported in this thread).

Another thing I'm seeing in the log - the aircharge fluctuations also begin when the wastegate cracks open.

Do you think it could be the wastegate actuator causing the problem? And would it need to be adjusted or replaced?

Or could it just be a tuning issue that needs adjustment?

[Spunkster]

I'm not sure.

[jeffx]

note that it appears to be overshooting the DIFP target by a fair margin and this could be causing the fuel duty cycle oscillations that I am also seeing (reported in this thread).

Another thing I'm seeing in the log - the aircharge fluctuations also begin when the wastegate cracks open.

Do you think it could be the wastegate actuator causing the problem? And would it need to be adjusted or replaced?

Or could it just be a tuning issue that needs adjustment?

it could be something with the wastegate flow characteristics. It could also be that the AFM tables are off, causing the aircharge calculations to be off which tends to have a cumulative effect which can snowball into causing many other issues. Have you tried tuning your AFM? If the AFM values are off far enough, your fuel trims will be too wonky for the ECU to correct, and the effect gets amplified with scaled MAFs like you have, so it's even more important to get the AFMs dialed in very accurately.

[pedal_r]

Showed my tuner the input from this thread.
Here's his response:
----------------------------------------
"I have taken settings from a setup I recently tuned (with the new software updates) successfully using your exact fuel system and turbo kit and applied them to your tune. This should get us VERY close, if not dead on. If its still way off, then it'll be pointing towards something mechanical as the culprit."
"I can make more adjustments obviously, but straying too far from this probably wont be ideal given the success of the other setup similar to yours."

"So, load this one up and lets cross our fingers!"
"Grab the standard logs please"
-----------------------------------------
attached the new log from the new tune file

[pedal_r]

note that it appears to be overshooting the DIFP target by a fair margin and this could be causing the fuel duty cycle oscillations that I am also seeing (reported in this thread).

Another thing I'm seeing in the log - the aircharge fluctuations also begin when the wastegate cracks open.

Do you think it could be the wastegate actuator causing the problem? And would it need to be adjusted or replaced?

Or could it just be a tuning issue that needs adjustment?

it could be something with the wastegate flow characteristics. It could also be that the AFM tables are off, causing the aircharge calculations to be off which tends to have a cumulative effect which can snowball into causing many other issues. Have you tried tuning your AFM? If the AFM values are off far enough, your fuel trims will be too wonky for the ECU to correct, and the effect gets amplified with scaled MAFs like you have, so it's even more important to get the AFMs dialed in very accurately.

Spunkster and jeffx could I please have your input on this datalog?
Its from using a different tune file from a different tuner. Same setup, just different tuner.

[jeffx]

on this 2nd log it appears that the wastegate behavior looks better. Your actual boost is tracking commanded boost bettter for the most part without as much hunting of the wastegate. and the HPFP is not overshooting command as much in this case, in fact now it's falling pretty well short of command in the final third of your pull. It seems that this calibration uses different fuel pressure tables than your other one.

The fuel trims are veering off course fairly early in the pull so at this point I would try tuning the AFM tables to improve the trims and see if that doesn't help your fuel pump and air charge situation.

[pedal_r]

on this 2nd log it appears that the wastegate behavior looks better. Your actual boost is tracking commanded boost bettter for the most part without as much hunting of the wastegate. and the HPFP is not overshooting command as much in this case, in fact now it's falling pretty well short of command in the final third of your pull. It seems that this calibration uses different fuel pressure tables than your other one.

The fuel trims are veering off course fairly early in the pull so at this point I would try tuning the AFM tables to improve the trims and see if that doesn't help your fuel pump and air charge situation.

Thanks!! Tuner resolved the air charge situation.....

[jeffx]

on this 2nd log it appears that the wastegate behavior looks better. Your actual boost is tracking commanded boost bettter for the most part without as much hunting of the wastegate. and the HPFP is not overshooting command as much in this case, in fact now it's falling pretty well short of command in the final third of your pull. It seems that this calibration uses different fuel pressure tables than your other one.

The fuel trims are veering off course fairly early in the pull so at this point I would try tuning the AFM tables to improve the trims and see if that doesn't help your fuel pump and air charge situation.

Thanks!! Tuner resolved the air charge situation.....

Can you share with us what the problem was? This information could help others down the road.

[pedal_r]

on this 2nd log it appears that the wastegate behavior looks better. Your actual boost is tracking commanded boost bettter for the most part without as much hunting of the wastegate. and the HPFP is not overshooting command as much in this case, in fact now it's falling pretty well short of command in the final third of your pull. It seems that this calibration uses different fuel pressure tables than your other one.

The fuel trims are veering off course fairly early in the pull so at this point I would try tuning the AFM tables to improve the trims and see if that doesn't help your fuel pump and air charge situation.

Thanks!! Tuner resolved the air charge situation.....

Can you share with us what the problem was? This information could help others down the road.

My tuner has not shared those details with me. I just sent him a screenshot of this thread with your input. He told me he took the same tune settings from another client's tune with the same mods. But I'm assuming he did what you suggested in the previous posts, tuning the AFM tables, but who knows.
We started this tune last year July, he insisted there was a potential boost leak or mechanical related issue. I was chasing this non-existent boost leak for the past year. I'm just so relieved it's now resolved.

[pedal_r]

Here's what the datalogs look like now. I notice the airC was turned down compared to before, now it's more stable.