E9X N55 BOV sound and car is "shaking"

gachdavit

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Mar 25, 2022
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Hello everybody,

I have a car 335i E90 {N55 PWG}.

My car had a lot of issues (But somehow, we started fixing all problems). The core issue was, that a car was going on boost very late and once it was boosted `target/actual` PSI was very far from each other (Target PSI = 18 / Actual PSI = 4, etc). I decided to replace turbo, and install another OEM turbo and here we go. I am feeling a lot of difference, BOV has a crazy sound (Even in neutral. It did not have a sound on old (bad) turbo) and difference is really significant. 1/2 gear is really crazy, so I can say that we really have a progress. After replace turbo, I feel first time that my car has a turbocharger.

My mods:

Turbo/Fueling: 100 % stock
Turbosmart BOV (Installed in turbo housing, not in chargepipe)
Wagner Tuning EVO II competetion
Catless Downpipe
ER Chargepipe
ER TIC pipe
BMS air intake
MHD stage2+ (98RON)
XHP stage3

A problem:
When I drive a car and start acceleration (Not very aggressive way, let's say it's cruising), I hear sound of BOV (pshhhh [delay], pshhhh [delay], pshhhhh [delay]) and this time car is shaking. On high RPM's this sound is gone. I have a feeling that, once car is boosted it releases air in no time. Today we tested system, no boost leak (Between Turbo and FMIC, TIC pipe is installed fine). Is there possibility, that reason is intake manifold or throttle body ?

I do not know, what else can be a reason.

Anyone has experience like this ?

Thanks !
 

doublespaces

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Oct 18, 2016
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2009 E93 335i
In both of those logs, you are overboosting and the throttle is closed until you're not over boosting and it opens then goes closed again because you overboost once more. This is causing the bucking sensation. If you've changed the turbos then maybe something is wrong there? I can't help with the N55 much unfortunately, I don't know how the boost control works but I would definitely double check how all that stuff was hooked up. Reversed wire, reversed vacuum line, etc. Just have a look at the throttle position in your logs and compare that to the boost vs boost target. You're making most boost than it wants. Accelerator pedal position is independent of the throttle blade as you may know, as it is a drive by wire throttle body.
 
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gachdavit

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Mar 25, 2022
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In both of those logs, you are overboosting and the throttle is closed until you're not over boosting and it opens then goes closed again because you overboost once more. This is causing the bucking sensation. If you've changed the turbos then maybe something is wrong there? I can't help with the N55 much unfortunately, I don't know how the boost control works but I would definitely double check how all that stuff was hooked up. Reversed wire, reversed vacuum line, etc. Just have a look at the throttle position in your logs and compare that to the boost vs boost target. You're making most boost than it wants. Accelerator pedal position is independent of the throttle blade as you may know, as it is a drive by wire throttle body.
Thanks for your time.

I googled this `bucking sensation` and I think this is what I feel during driving.

1. Spark plug/Ignition coils are not in bad conditions, I can say more they are almost new.
2. Air intake gonna be replaced or cleaned.

First I am going to replace aftermarket `Turbosmart` BOV with OEM one, maybe this will fix an issue. If not, it's time to touch fuel pumps, ahhh.

Thank you !