Wastegate "flutter" issue is driving me crazy.

[STernax]

Hopefully this is the right sub-forum for this. If not, Mods please advise.

Ok, so I've been searching for months on this forum and most of the Subaru ones also (they have terrible wastegate flutter). i'm getting fluctuating boost in 3rd and 4th gear when wot. Boost oscillates between 21 & 24 psi.
I noticed it the day I did my muffler delete, but it could have been going on earlier, but less pronounced. I was running an OTS tune at the time I first noticed it.I know that tiny turbo are easily affected by backpressure, so I've done a few things to try and smooth it out. I added a 3" DP, removed my BOV spacer, added a WGA. Initially, I tightened my stock WGA, and that seemed to make it better, but still exists. I don't thin kanything is wrong with the car, so to speak. It's just a little annoying. I wrapped up my protune last week and the car feels SO much better now, but the "flutter" feels awkward. The last part I'm waiting on is a Cp-E exhale kit with HKS BOV. I think I've exhausted my wife tolerance with chasing the issue. Lol. Do you guys have any ideas? BTW, my WGDC is 90 @ wot. I don't want to tighten it anymore. Peak boost spikes around 26 and settles into 24 very nicely, when there is no flutter.

Current setup is:
K&N panel filter (stock box)
RamAir intake tube
Whoosh crossover pipe
MBRP hot pipe
TS WGA
UR catless DP
VT Big Mouth
CX FMIC
Muffler delete
Protune

 

[JDG]

This is with the OEM turbo? Who is your "pro-tuner"? I would also like to see what your WGDC and ETC angle are doing during a datalog.

 

[STernax]

This is with the OEM turbo? Who is your "pro-tuner"? I would also like to see what your WGDC and ETC angle are doing during a datalog.

Yes, stock turbo. I'm not trying to call out my tuner though. He's very well respected and produces quality work for our community. Car was doing the same thing, but worse on the OTS tune. I can send you one of my logs. IIRC, WGDC bounces between 86 & 54.

 

[BDVRanger]

I had this happen when I ran the stock bov. I run 25 to 27 pounds of boost on the stock turbo and found that the stock bov didn't hold up. I went to the 50/50 plumb back and my problem was solved so it might help you.

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[JDG]

This flutter you are describing is under wide-open-throttle correct? Not when you let off the gas to shift.

 

[STernax]

I had this happen when I ran the stock bov. I run 25 to 27 pounds of boost on the stock turbo and found that the stock bov didn't hold up. I went to the 50/50 plumb back and my problem was solved so it might help you.

Sent from my SM-G965U using Tapatalk

I'm really hoping the cold side pipe will solve the issue. I've tried to have faith in the stock bpv, but I've never liked them.

 

[STernax]

This flutter you are describing is under wide-open-throttle correct? Not when you let off the gas to shift.

Exactly. Boost fluctuates with WGDC. My dyno charts with the OTS map related this also.

http://imgur.com/a/jQY2LXm

 

[JDG]

Exactly. Boost fluctuates with WGDC. My dyno charts with the OTS map related this also.

http://imgur.com/a/jQY2LXm

A tuner let you leave the shop like this? Jeeze


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[FORZDA 2]

The problem is in the "tune". The tuner is trying to use the oem wastegate duty cycle tables and they don't work well with mods, especially the aftermarket actuator. I don't know which tuner you're using, but any one worth a damn will solve it real quick. If you want, I can fix the tune for you, but you should go to your paid tuner first. You will need to run some data logs to show the problem.

 

[STernax]

A tuner let you leave the shop like this? Jeeze


Sent from my iPhone using Tapatalk

Not at all. This was from my OTS tune. No way I would've accepted that. It was 80* yesterday and in the 70's today, and I had no flutter. Completely perplexing.

 

[STernax]

The problem is in the "tune". The tuner is trying to use the oem wastegate duty cycle tables and they don't work well with mods, especially the aftermarket actuator. I don't know which tuner you're using, but any one worth a damn will solve it real quick. If you want, I can fix the tune for you, but you should go to your paid tuner first. You will need to run some data logs to show the problem.

I may have to take you up on this. The weirdest part of it is that it doesn't happen every time. Even some of the revisions had it smoothed out. I really want to wait on my cold side + bov to arrive and see if it's gone. Ever since the temperature got above freezing, I haven't seen the issue. It seriously went snowing to 80* in a few days.

 

[FORZDA 2]

Not at all. This was from my OTS tune. No way I would've accepted that. It was 80* yesterday and in the 70's today, and I had no flutter. Completely perplexing.

The ECU doesn't target the boost pressure, it targets the Torque to Load and Load to Torque requested from the pedal input and the atmosphere conditions at that time. In warm weather, it takes more boost to hit the targets, so the WGDC is essentially maxed out and it seems "smooth". In cold weather the boost required to hit the targets is much less, so the ECU must modulate the boost to hit the requested targets without going over. This constant adjusting of the boost and throttle plate by the ECU (using the OEM tables) is quite susceptible to the oscillation you're seeing. Several tables may need to be adjusted. It may be that the Torque and Load limits are set too much lower than the max WGDC allowed. It is quite easy to fix when you have the tuning capability and the actual data from the particular setup.

 

[STernax]

The ECU doesn't target the boost pressure, it targets the Torque to Load and Load to Torque requested from the pedal input and the atmosphere conditions at that time. In warm weather, it takes more boost to hit the targets, so the WGDC is essentially maxed out and it seems "smooth". In cold weather the boost required to hit the targets is much less, so the ECU must modulate the boost to hit the requested targets without going over. This constant adjusting of the boost and throttle plate by the ECU (using the OEM tables) is quite susceptible to the oscillation you're seeing. Several tables may need to be adjusted. It may be that the Torque and Load limits are set too much lower than the max WGDC allowed. It is quite easy to fix when you have the tuning capability and the actual data from the particular setup.

Thank you for this insight and information.

 

[STernax]

Just to come full circle on this topic, I have fixed the WG flutter. I got under the car on Sunday and loosened the nuts to the point that I was only seeing 1.8psi. I kept putting it up on ramps and driving to the lake until I I got it to sppike to 25.9, no fluuter, and holding 22-23psi. Car is running like a dream. Time to go back to the dyno.