[fsd350]

Guys, have a boost issue. When accelerating from a stop my boost never gets higher than 30 psi. If I am pulling hard from 60 to 100 or so (torque pull rather than high RPM) I see a flutter in the gauge at 30 psi, increases to about 35- 36 and then dumps boost to 30. Seems like some bad behavior with pressure converters to me. I am using a quality Autometer boost gauge. Some info on my 335d:

Mileage is 74k, tuned with Jarek's 2.5 and deleted since about 54k. Ported wastegate due to some feedback early on when we started tuning and deleting a few years ago fearing turbo ovespeed. (not necessary). No issues with running, starting, driveability, no codes shadow or otherwise except for occasional overboost code and partial shutdown when in 6th and pulling hard uphill (100-120). The reduced power warning would go away in a couple seconds and return to normal rather than having to restart. Only happened 3 only this year.

Now have JR stage 2.8 and Xhp tranny tune Stage 3. That issue has not returned. Just the boost deviation. Don't believe I have any boost leaks. I check when I do an LOF. Recently upgraded intercooler and installed new seals. No change. Drive pressure peaks at 44psi which seems high.(Using DWR's Torque parameters.) Have been up to 160 on GPS no problem racing a Shelby Cobra when we backed off.

Thoughts? (Hopefully I am not duplicating issues already shared and solved)
Thanks in advance

[Yozh]

So the reduced power does not pop a code?

[fsd350]

Sorry Yozh, that would help. 4521 Charge Pressure Control Error. Meant to say only happened 3 times last year never to return. Not sure why it peaks and drops so fast. What is up with the flutter? I know you've done some extensive logging.

[Yozh]

So no more code? But you still get limp and flutter? If I recall (not at the computer right now) 4521 is an overboost code. Would your flutter happen to come on at after 3000 rpm? How healthy is the vacuum system? Do you have a way to log your parameters? You e mentioned boost deviation. Are you logging actual vs requested vs exhaust pressure?

[fsd350]

No more codes since issue last year. Limp was only a few seconds before returning to normal, which was odd to me. Usually would require a restart in limp mode.
Boost flutters a second at most 30 psi, increases to 36 or so right away, before immediately dropping back to 30 psi.
Correct, 4521 Boost Pressure Actuator - Regulation Pressure too High. Will check RPM, seems to occur only on 6th gear pull, pedal depressed to kickdown switch in 6M.
Vacuum system seems ok, but have not replaced all of the hoses, only some. I meant deviation as "not the norm", rather than a pressure delta. I'll get some logging compiled.

[Yozh]

Do you know which parameters to log? I also as a precaution would test your vacuum actuators pressure converters and switchover valves in driving. Fairly easy to do.

[fsd350]

Requested Boost and Actual(Boost Delta)? it cuts boost 30 psi. Should be 36-37 on the 2.8 tune without dropping to thirty
I Use Rheingolld and will piggyback on to Testo, Also have Cbarly sovewhat worthless) foxwell, and BT too, when Idon't fell like lugging ny latop around,
I recheck the vacuum the vacuum actuators and switch overs.

thanks for your help

[Yozh]

Log:
Boost actual
Boost requested
Emp
Turbo switchover duty ratio
Compressor bypass status
Rpm.

[duramaxtoo]

Did u ever find the source of your problems?

[fsd350]

Unfortunately, I have not had a chance to log. A lot going on at work and not my DD.