Pretty much what he said in shortened form..

The sound you are hearing before the BOV kicks in is not compressor surge... but the wastegates opening.. the woo wooing sound is them opening at different times... you wont hear that in a single turbo setup. thats why if you ever heard a turbo kit before it didnt do that probably because it was a single...

Does this make sense? Sounds like it does..... he's the one who installed it... he's done about 7 Turbo kits.... but its the first TT hes done...

Hope thats the answer....

 

Anthony...sorry..this is not true.

The wastgates arent even opening up until 5.6psi or so.

So for example, if you floor the car in 2nd gear until boost reaches 4psi, the wastegates are still fully closed, so if you hear the compressor surge...its not the wastegate. Also, even with TT, the wastegates dont make that noise....the wastegate opens and the exhaust ends of going back to the downpipe and out your exhuast.

Have you tried tightening all the way, the loosening all the way, and seeing how the BOV responds?

Anthony, one other thing it could be is that exhuast leak we talked about at the wastegates. My car makes a bit of an exhuast leak sound on decel......sounds like a sqeaking belt.

Just a thought.

Hth,

Sharif

 

I am not going to comment on the noise your car is making, since I have not heard it with my own ears.

However I will say that GQ (sorry, not trying to pick on you) is wrong. The wastegates start to open immediatly as boost pressure starts. Any boost at all and they begin to open.

The only time this is not true, is if you have a well adjusted electronic boost controller. This is why EBCs can spool turbos faster. Because when adjusted correctly, they will keep the wastegates closed until right before target boost is acheived. This means that more exhaust flow is ulitilized to help spool the turbos to make target boost sooner, rather then dumped out the wastegate prematurely.

If the sound you are hearing is a fluttering sound that stops immediatly as the BOV opens, thats compressor surge. I love the way it sounds. If your really curious to prove that that is what your hearing... tighten up your BOV and see if you hear more of it... that should show you right there.

-Charles

 

i have the shhh shhh, shh shh also. i have open wastegates, so i know its not them... it would be loud like when i boost i also have a profec boost controller, so there is no way its the wastegates.

it is definitely compressor surge. it only happens at non load engine running (but not idle).

i was told this is caused on twin turbo setups only... as what is happening is the compressors are making positive pressure in the intake pipes, but the throttle is not open very much. this causes each compressor to surge back and forth, as there is no other place for the air to go.

i was also told this compressor surge is not bad as when it happens between shifts on non-BOV'd cars.

hth,
michael

 

oh yeah.. the PE TT kits do this also (i have heard BBBT's car, and cheston mentioned this also). i have also heard it in a TT supra (non-sequential) setup.

i like the sound, also...

 

skiddazzle said: i was also told this compressor surge is not bad as when it happens between shifts on non-BOV'd cars..

well now I have one....it still does it until the BOV opens

but.... yeah I really think the sound is cool.... i just dont like the fact that its compressor surge...... sometimes its one sound... and sometimes its wavy.

Any other suggestions.... as I have asked 3 mechanics already... one of them worked for Garrett... he didnt know what it could be either.... im just afraid to turn up boost if its compressor surge.. could turning it up and having a boost controller possibly get rid of it?

 

sounds like you are saying it happens all the time...?

first off, i have not heard a greddy tt kit do this... only mine, and the PE TTs.

the reason...?
my kit and the PE kit have both compressors joining into a single pipe, and then it goes into the i/c as one air stream... in the greddy kit, both compressor pipes go into the i/c individually... this allows for more space for the compressed air to expand into, so there is no compressor surging happening (for any of the 5 greddy kits i have seen).

oh yeah... mine only happens at cruising, with the throttle mostly closed. it never happens when i am romping on it. it also never happens on decel either.

hth,
m

 

Hey Charles,

Are you certain this is the case with external wastegates? That's the one benifit of external wastegate vs. internal. External tends to have better boost response since the pressure builds quickly to the spring preset weight (about 5.6psi on the Greddy), and the wastegate opens and vents exhuast after that. It is a straight dump into the downpipe/exhaust track.

I cant see how or why the wastegate would open prior to that...OK...maybe it opens a tad.

Can you clarify it for me?

 

I am about to go to bed, I will try and go more in depth tommarow...

but if you wanted to sample it, take a test drive in a car with an atmospherically dumped external wastegate with boost controller turned off, and drive it around. You will immediatly hear it... as you start to build boost the wastegate starts to open... its very apparent with an atmospherical dump of course, because it sounds like a very loud exhaust leak.

I cant even think of how many external gate external vent cars I have put together... that sound is one of my favorite turbo sounds

 

Hmmm...Skidazzle is our resident "atmospheric dump wastegate boy"......car to comment on what yours sounds like?

 

okay.... the noise im getting on acceleration is like was quoted.. like an exhaust leak..

On decel someitimes under sudden boost conditions... like when i floor it all of a sudden and i take my foot off the gas...

The best way to describe it is... listen to the smashing pumpkins song 1979.... theres a certain part throughout that song that sounds very very close to the sound im hearing on decel... but in the song its a little lower pitched than the actual sound... take a listen and see what you think

 

sounds like a jet when my wastegates open... it different than the "shhh shhh, shh shh, shh shh.." i get when just cruising around.

m

 

Brusch...I think you have a leak at your wastegate. Those paper gaskets are crap.....mine sorta made that noise when I had the leak. As you know, its only a matter of time before the stock Greddy paper gaskets will completely blow out. I think your BOV is fine..and normal...but you should probably address the wastgate gaskets at some point. Good luck!