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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > N54 Noise Coming Off Accelerator Quickly Under Boost



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      09-28-2022, 06:38 AM   #1
CantSitStill
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N54 Noise Coming Off Accelerator Quickly Under Boost

Hi Everyone,

Really hoping someone has seen this before and I can help me

I have been having a strange problem for some time now that I cant find any information on, maybe because its hard to describe or take a recording of. Basically what is happening is when Im under moderate boost/acceleration at say 20-40mph, if you lift off the pedal quickly (instantly straight off) the car will make a short (split second) cough noise almost like the turbos are stalling (it sounds like someone making a crap fake coughing noise). It does not do it at higher boost levels, and it does not happen all the time.

Now here is what I have tried:

1. Upgrading trial tial BOV with a weaker spring and giving it a bigger vacuum hose tail in the manifold this helped the bov react quicker but not the noise
2. Adjusting the wastegates I had tightened these on my old turbos, so I loosened them a bit this helped a little, but it was still there
3. Upgrading my turbos to 19ts wastegates were properly calibrated and noise is still there
4. Upgrading to an RB PCV valve made no difference but old one was leaking bad
5. Adjusting the base duty cycle (menu 12) on the JB4 this seems to help/cure but I need to lower the setting way down (to like 1500) so I think its masking the issue rather than it being directly related to the wastegate position
6. Using a different tune (MHD/Wedge custom) worse with flash only as JB4 settings are not masking the issue

To me it almost sounds like the turbos stalling a little in the split second before the BOV reacts, so MAYBE either the throttle body is closing too fast or the wastegates not reacting fast enough for coming off the boost. They need a lack of vacuum (atmosphere) to open the wastegates so im thinking boost solenoids next??

Any advice what to try next welcome, I'm worried about my new turbos now especially if they are stalling

Cheers
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      09-28-2022, 08:13 AM   #2
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Found this where you can hear it:

Right before the bov goes off you can hear the sneeze/cough



Theory here is it was caused by my inlets?:

spoooooolstreet_dot_com/threads/new-inlets-and-catch-can-installed-now-tial-bov-sounds-horrible-why.7362/page-2#posts

POST 29.

Seems its normal???
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      09-28-2022, 11:01 AM   #3
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Quote:
Originally Posted by CantSitStill View Post
Found this where you can hear it:

Right before the bov goes off you can hear the sneeze/cough



Theory here is it was caused by my inlets?:

spoooooolstreet_dot_com/threads/new-inlets-and-catch-can-installed-now-tial-bov-sounds-horrible-why.7362/page-2#posts

POST 29.

Seems its normal???
I remember seeing another member that had very funny blow off sounds due to the inlets. They Echo weird almost causing a screech sound.
On a side note you may want to clean and lube your BOV. Looks a little sticky when opening/ closing but I could be wrong.
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      09-29-2022, 07:18 AM   #4
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Thanks. Its not actually my BOV, mine is new and well greased. Over on spoool street I found some interesting chat where, as you say others are getting weird noises right before the BOV goes off. It seems like its common after the inlets are installed but its definitely not normal as I had a 335i before with inlets etc. and it never did it at all. I used a symantec bov on that car although, however I tried that on this 335i and it made it sound worse.

I noticed this in my logs today:

https://datazap.me/u/stuie1982/jb4-b...9&zoom=409-459

There is a weird step in the throttle when coming off the gas so I wonder how much of it might be to do with the throttle bodies getting old and not returning quickly enough to base %. Going to see if I can capture it more in some logs and maybe clean the TB
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      10-01-2022, 10:52 AM   #5
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Hello,

So short story is i have completely solved my issue and returned the instant whoosh of my tial BOV. Its completely transformed it. The turbo back pressure noise is gone and BOV reacts instantly when you have the foot off the gas. Its also back to working at lower RPM's/Speed again. Boost and WGDC are the same (20psi) so i assume its not leaking boost as well. To say im happy is an understatement!

I did try the synapse connected to 2 vacuum sources and one boost source and it was still crappy.

Anyway here is how i modded the bov:

1. The piston was not able to travel up all the way and was only ever half open - i opened is up and shave off 5mm from the internal guide pin, i had to take a bit off the guide pin and the outer sleeved the guide pins moves up and down. This enabled the BOV to open much wider
2. The outer sleeve inside the BOV has 2 holes in it to allow air vacuum to suck the BOV open. I drilled these holes bigger with a 5.5mm drill
3. The banjo i drilled with a 5.5 MM drill to make the hole bigger and the banjo bolt i drilled as well bigger
4. I shorted the spring by about 20mm by hacksawing a bit off - you might not need to do this so i would try the above first
5. When i put the banjo bolt back on i made sure the large hole i drilled was perfectly lined up with the banjo bolt
6. As before i have 2 separate vacuum sources coming from the manifold to the BOV ensuring you have a fat T piece being used.

Its important there are no bottlenecks for the vacuum source.

Anyway, as i say im shocked at the difference this has made and has fixed all my issues. BOV sounds amazing again and so do my new turbos.

I assume a real Tial bov would not have these issues, pretty sure mine is fake. What i would say if you have a real one buy a cheap fake one, make the mods and see if its any better.

Cheers
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      10-03-2022, 08:22 AM   #6
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Quote:
Originally Posted by CantSitStill View Post
Hello,

So short story is i have completely solved my issue and returned the instant whoosh of my tial BOV. Its completely transformed it. The turbo back pressure noise is gone and BOV reacts instantly when you have the foot off the gas. Its also back to working at lower RPM's/Speed again. Boost and WGDC are the same (20psi) so i assume its not leaking boost as well. To say im happy is an understatement!

I did try the synapse connected to 2 vacuum sources and one boost source and it was still crappy.

Anyway here is how i modded the bov:

1. The piston was not able to travel up all the way and was only ever half open - i opened is up and shave off 5mm from the internal guide pin, i had to take a bit off the guide pin and the outer sleeved the guide pins moves up and down. This enabled the BOV to open much wider
2. The outer sleeve inside the BOV has 2 holes in it to allow air vacuum to suck the BOV open. I drilled these holes bigger with a 5.5mm drill
3. The banjo i drilled with a 5.5 MM drill to make the hole bigger and the banjo bolt i drilled as well bigger
4. I shorted the spring by about 20mm by hacksawing a bit off - you might not need to do this so i would try the above first
5. When i put the banjo bolt back on i made sure the large hole i drilled was perfectly lined up with the banjo bolt
6. As before i have 2 separate vacuum sources coming from the manifold to the BOV ensuring you have a fat T piece being used.

Its important there are no bottlenecks for the vacuum source.

Anyway, as i say im shocked at the difference this has made and has fixed all my issues. BOV sounds amazing again and so do my new turbos.

I assume a real Tial bov would not have these issues, pretty sure mine is fake. What i would say if you have a real one buy a cheap fake one, make the mods and see if its any better.

Cheers
What in the h**l is going on here?? In what world does anyone need to do this to a functioning BOV? Sounds like a defective unit or off brand junk.
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      10-03-2022, 08:54 AM   #7
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In my world. It's something to do with the car. The bov is fake but works well now. The synapse bov (one of the best you can buy) was worse. On my last 335i same bov worked perfectly with just the standard vaccume source coming off the manifold
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