Technical Partial Throttle Surging/Oscillation Noises from BOV

cityazndan

Corporal
Jan 17, 2017
107
14
0
Ride
2016 340i xDrive
Hello,

Is there a way to tune out or alleviate partial throttle boost oscillation? I have the VS MAP sensor relocate on deck but was wondering it this is a tune issue. Right now, I'm stacked JB4 with MHD BEF.


The sound is exactly like in the video car (0:12 - 0:17 seconds), turn up the speakers to hear the audible oscillation, almost surging. I have logs as well capturing the oscillation between 1.3-1.7psi. Sounds bloody awful cruising around.
 

Torgus

Brigadier General
Nov 6, 2016
2,671
2,194
0
Boston
Ride
ACF 6466 E92 + METH
Bov line upgraded?

Correct spring in there?

Can you grab a buddies bov and see if it reacts the same way?
 

dyezak

Major
May 4, 2017
1,767
1,518
0
Plano TX
Ride
335is
Sounds like BOV flutter. Need a full 1/4" line from your intake manifold to the BOV. Tial has made it pretty clear on the tech sheet they require this http://tialsport.com/documents/w3_tial_qqr_sp.pdf

And as much as you might not like him, Tony Vargas has addressed this on many occasions as well explaining why the Tial needs a full 1/4" line.
 

cityazndan

Corporal
Jan 17, 2017
107
14
0
Ride
2016 340i xDrive
Right now I'm using a Synapse BOV, I have my buddies Tial QRJ on hand. installing the VS adapter is similar to tapping the manifold. I have a 1/8 to 3/8 barb from the adapter so it matches the 3/8 (10mm) end from the Tial. Currently using verocious Motorsports platinum cured vacuum hose. Will get 6mm ID hose next. My only concern is why are we using a 1/4 (6mm) dedicated line when the barb end if 10mm....unless the barb end ID is 6mm....
 
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doublespaces

Administrator
Oct 18, 2016
9,304
4,334
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AZ
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2009 E93 335i
1/4 line absolutely necessary. I use a very light spring also, there is no reason to use a tight spring, its not going to kill your car to have the bov open at idle.
 

cityazndan

Corporal
Jan 17, 2017
107
14
0
Ride
2016 340i xDrive
The Synapse BOV isn't designed like the Tial (pull valve), but my buddy's Tial has the OE 3lbs spring. I might re-install the preload spring for the Synapse as big boost guys take it out (PO was running 33psi on a Xona).
 

themillsbros

New Member
Jan 26, 2023
3
0
0
Changed to port B seemed to alleviate some of the noise, cranked down the adjustment screw, back to making that noise.... Looks like ill be looking at new bov/pipe =\