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Discussion Starter #61
From what I'm understanding, your blow off valve adjustment may have introduced a leak that's bringing you back to the "right" of the surge line. This will work fine, for a speed density tune. It may work for a MAF if it's a metered leak. If you turn up boost eventually, let us know if you encounter this again. If you have tuning issues, keep this in mind as a possible issue.
I only say this, because during full throttle, your BOV doesn't do anything, and any adjustments shouldn't change full throttle characteristics.
Since the BOV is before the MAF, if it is a leak, it is a metered leak.

What bov Do you have? I don't see how the bov would affect anything. It should be closed under boost.

Or are you saying the bov was fluttering when you released the throttle, so you softened it up?

I looked at the log and don't really see anything jumping out. Boost looks pretty solid at 8psi from 3800 until you let off at 4100?

Was this a wot pull? The tps only shows like 48%
The BOV thing is something I read online and decided to try, I don't see how it would effect WOT either. The BOV is a Turbosmart VeePort Pro.

The log was not a WOT pull, I didn;t go heavier throttle when I heard the surging starting, and backed off after a bit.
 

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Since the BOV is before the MAF, if it is a leak, it is a metered leak.
So I read this then looked back at some of your pictures. You MAF is right before the throttle body. Shouldnt it be on the air intake going into the turbo inlet?

I've never seen a MAF setup like that before. It is receiving boost so maybe it's maxing out the reading and causing your problems?

I wonder if a speed density tune would work better for this setup?

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Discussion Starter #63
So I read this then looked back at some of your pictures. You MAF is right before the throttle body. Shouldnt it be on the air intake going into the turbo inlet?

I've never seen a MAF setup like that before. It is receiving boost so maybe it's maxing out the reading and causing your problems?

I wonder if a speed density tune would work better for this setup?
I've read both, and both locations are optimized for their own reasons. If it is maxing out the readings, the local shop recommends moving to a bigger MAF housing to reduce flow speed. But maxing out the reading doesn't explain the sound and the fact that the car seems to run fine during the surging.

Speed density would've made this whole thing a lot easier, but Ktuner did not have speed density available on the AT cars. AFM had to do.
 

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I've read both, and both locations are optimized for their own reasons. If it is maxing out the readings, the local shop recommends moving to a bigger MAF housing to reduce flow speed. But maxing out the reading doesn't explain the sound and the fact that the car seems to run fine during the surging.

Speed density would've made this whole thing a lot easier, but Ktuner did not have speed density available on the AT cars. AFM had to do.
I wondered if MAF could be used after turbo, that's awesome. This may be common for all I know.
Also makes it nice that if your BOV is leaking, it's not going to affect your tune. Sounds like its fixed for now, I'm still very curious what the original cause was.
 

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Discussion Starter #65
So my tuner suggests that it could be related to the spring weight in the WG and the WG size. With an internal WG, not too much I can do about the size, but I will play around with different spring weight and pre-load tmr and I'll let everyone know how it goes.
 

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Discussion Starter #66
So here is the sound that I'm hearing.

IMG_8437.MOV

May need to turn your volume up to hear it. It is toward the end right before my BOV half-a**ed went off.
 

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So here is the sound that I'm hearing.

IMG_8437.MOV

May need to turn your volume up to hear it. It is toward the end right before my BOV half-a**ed went off.
Honestly, I didn't really hear much. Sounded like turbo spool then the wg opening?

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Discussion Starter #68
Honestly, I didn't really hear much. Sounded like turbo spool then the wg opening?

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Right before the WG opens, there is a chatter like sounds. I know, much more pronounced in person.
 

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Right before the WG opens, there is a chatter like sounds. I know, much more pronounced in person.
I hear the compressor surge, before the top of rev range.
So, you've introduced a leak with the BOV adjustment, and it's gone at low RPM. Still shows up at high RPM. Could be the leak flow rate doesn't change, but engine flow rate does.
I really think exhaust needs to be checked. I say this, as it looks like exhaust gasses could easily bypass the WG if you have too much backpressure.
You understand gas theory, so I'll go farther. A turbo works, because what the compressor does, is multiplied on the turbine side. This is how we make boost.
So, if there's too much backpressure, can the exhaust bypass your IWG? It looks, like it's not biased towards going through the wastegate without a large pressure difference.
At high flow rates, exhaust not escaping the cylinders. Compressor is still spinning fast, but the cylinders are still filled with exhaust.
If this is true, your missing out on power, which would be a benefit.

I don't understand myself, how the compressor wouldn't just create overboost, but I assume this is why compressor maps have a surge line.
 
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Discussion Starter #70
So I took the Catback off today. I don't think I hear the surge again but the car is also super loud so can't be 100% sure, @9thgensifamily was right, I definitely left power on the table. The car now spins 2nd. The mic was placed about 4 inches above the turbo.

Heres the audio recording for today, time to listen for are:
1:32
1:45
2:04
3:43
3:49
4:23
4:57
5:43
5:48

 

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Discussion Starter #71
Because how loud the car was, I'm not 100% sure. I'm going to rig up a spare MAF sensor that I have before the turbo to an Arduino to monitor the air flow before the turbo as the car does not monitor that. This way I can confirm if there is a compressor surge or not.
 

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Yeah, it's super loud. Hopefully you can figure out a way to sense the surge.
 

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Discussion Starter #73
Quick Update:

I couldn't find a place to place the spare MAF and MAF housing that I have without running without a filter, and I didn't realize the turbo screen guards were so expensive. So instead, I bought a Yonaka 3" catback from a 9th gen SI owner near me and modified it to fit the car.

492122
 

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Quick Update:

I couldn't find a place to place the spare MAF and MAF housing that I have without running without a filter, and I didn't realize the turbo screen guards were so expensive. So instead, I bought a Yonaka 3" catback from a 9th gen SI owner near me and modified it to fit the car.

View attachment 492122
Your making me feel lazy. You unturbod, re-turbod (bigger), and custom making exhaust from pieces of another car!

Let us know results.
 
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Discussion Starter #75
Another quick update:
The welding is taking longer than expected.
I made 3 passes at National Trail today. Solid improvement over the smaller turbo.
492239


I'm car 212 on the left in all 3 passes.
Car 213 was a 2011 328i 6MT
Car 3931 was a Challenger Superbee 392
Car 352 was a GTO drag car

Run 1 and 3 was a simple foot off the brake then onto the gas launch
Run 2 I brake torqued the car for launch at around 2000rpm. It could've been the best run, but the initial IAT got too high while we waited for an oil spill to be cleaned up and the track to be re-prepped.

Edit:
It's worth noting that I ran with the roof rack on the car for consistency sake.
 

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Discussion Starter #76
...
The exhaust was completed today. Costed much more than anticipated. It is very loud and boomy during cruise and low throttle. High throttle is good. More importantly, it did not fix the issue with the sound on the turbo. Is it safe to say that what I'm hearing is not actually a surge as the exhaust is as open as it could be? Can I try a manual boost controller to see if it is a wastegate flutter?
 

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Sorry to hear it still exists. I can't find any info on what causes it if it's flutter. Is there a reputable tuner you could ask about it, and maybe they'll ride in it and have more insight?
 

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Can't hurt to toss a mbc on and see if you can get the boost turned up a bit.


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Discussion Starter #79
Well, the boost controller made no difference. I was hoping if it is the WG doing something weird, the controller can dampen the effect.
 
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