Compressor Surge/Turbo Flutter on S55

[crysys]

Hey guys,

I have a 2017 M4. I’m getting a turbo flutter under load and from the research I've done I'm trying to confirm if it’s compressor surge. It happens on the highway around 75–85 mph while accelerating and will continue to happen until lift. The sound is on throttle, not on lift. It does not happen in other pulls..at least that I am able to hear.

BM3 logs show boost target and boost actual usually track, but I think that when the flutter starts, boost actual oscillates around target (I'm not an expert at reading logs, and it's pretty small).

Recent changes: upgraded charge pipes, catless downpipes, intakes, and moved from BM3 Stage 1 93 to Stage 2 93 AGG. I checked fittings and pipes after some hard pulls and nothing is loose or disconnected. I have not pressure/smoke tested the system.

I've attached BM3 logs for the highway pull, 2 videos to hear the sound (below), and a line chart made from the BM3 logs. The BM3 logs show the flutter/surge twice.

Anyone with stock turbos and bolt-ons seen this? Is this normal behavior at high gear load, a leak I should test for, or something more serious?

Thanks!

Videos:
https://youtube.com/shorts/-0qteiWOFeQ?feature=share
https://youtube.com/shorts/mnzHDVxqbg0?feature=share

Google Sheets BM3 Logs:
https://docs.google.com/spreadsheets...it?usp=sharing

[M4COMPETITION]

I had this same exact issue, it turned out to be the J pipe and the fitment, it was boost leaking around the throttle body

[crysys]

Originally Posted by M4COMPETITION

I had this same exact issue, it turned out to be the J pipe and the fitment, it was boost leaking around the throttle body

Awesome, thanks for the reply! I'll go readjust it now

[crysys]

Originally Posted by M4COMPETITION

I had this same exact issue, it turned out to be the J pipe and the fitment, it was boost leaking around the throttle body

Unfortunately, this did not fix the problem. I reassembled the intakes and charge pipes (hot/cold) to ensure they’re properly fitted and all clamps torqued down. I also tried switching maps from Stage 2 93 AGG to Stage 2 93. I don't have a full exhaust, only downpipes, so I was thinking maybe too much back pressure is causing the compressor surge.

After a test drive with WOT in 3rd, car onboard system showed 320HP max and I’m still hearing the compressor surge noise in 6th on the highway.

No idea what I should look into next.

[NSX2M4]

If I'm reading this correctly; your boost levels have a huge dip and then shoot to the moon. (don't really know BM3 logs) You're at nearly 40 PSI at one point and your waste gate cycle is at 1%.

If I'm correct, I would focus on the waste gates.

[TSL]

I have a similar noise but just assumed it was normal, any solution?

[NoorSinghJohal]

Does it happen in sport+ only ?

I think it’s normal in sport + where it’s targeting more boost and makes that nice to relieve some pressure. Shouldn’t do it in efficient or sport.

[crysys]

Originally Posted by TSL

I have a similar noise but just assumed it was normal, any solution?

Not yet, just performed a smoke test and not seeing any leaks.

How long has yours been doing that? I'm nervous to drive on it but it's my daily.

[crysys]

Originally Posted by NoorSinghJohal

Does it happen in sport+ only ?

I think it’s normal in sport + where it’s targeting more boost and makes that nice to relieve some pressure. Shouldn’t do it in efficient or sport.

It happens on sport/sport+. Haven't tried it on efficient yet

[crysys]

Originally Posted by NSX2M4

If I'm reading this correctly; your boost levels have a huge dip and then shoot to the moon. (don't really know BM3 logs) You're at nearly 40 PSI at one point and your waste gate cycle is at 1%.

If I'm correct, I would focus on the waste gates.

All good, but the waste gate holds at 99% until I let go of the pedal. The lowest the waste gates went is 35% in the charts/logs.

[TSL]

Originally Posted by crysys

Not yet, just performed a smoke test and not seeing any leaks.

How long has yours been doing that? I'm nervous to drive on it but it's my daily.

Pretty much as long as I can remember. Have owned the car for 2+ years

[TSL]

Any update ?