I have this issue for quite long tine now and couldn't Where it comes from
It's a tssssssssss tssssssssss tssssssssss sound that I first thought was a hose leaking. I checked boost and there is no leak.
It sounds like the VTG mechanism retards under full acceleration between 3-4k rpm.

I don't have any power loss, it's just the sound that annoys me

What else could it be ?

 

ummm its weird , are you sure you do not have leak , maybe vacum leak !!

 

Does it happen only under wide open throttle acceleration? If so, it could be the sound of your compressor wheels cavitating under too much boost. IIRC you're running pretty high boost, right?

 

Vacum under acceleration ?

 

Torn BRV's?

 

i thought you were runing normal ..

ummmmm its your BRVs .. check them , what brand ??

 

It could be the BRVs, I think they are standard issue

 

Mine makes the same sound, noticed it goes away when using race gas, maybe its something to do with the engine management

 

That's different, when using racefuel the ECU changes map, more timin,boost etc. Then when shifting to pump fuel you need to pull the battery for 10min so the ECU will have to relearn and use the new values (pump fuel) if you don't do that then you'll have knock and BRVs open and let boost out to avoid engine fail.

In my case I hear the same sound 'like when BRVs open and let boost out' but my boost hold high up, no boost drop. Maybe it lets out very very little, you can barely hear it.

How could the BRVs be responsible for that? I though that f that was because of BRVs then I would had this problem all the way.
This is not the case, I hear that sound from 3 to 4k rpm before and after that everything is perfect.

It is more noticeable when manually shifting in 3rd or 4th and go full throttle from 1500rpm to red line

 

Does it happen at partial throttle? If sounds like turbo surge....

 

No, only under Full throttle

 

Could be surge or cavitation, been there seen that a few times.

 

How do I check it?

 

You need to lower boost between 3200 and 4000 and see if the noise goes away. or an ultra hi speed datalogger to check intake temperatures at the revs this is happening at. If you can read unfiltered intake temps, they'll be going up and down just as the noise is happening

 

I will check that, thank you. I have installed a boost gauge, and the boost looks good and stable. Is there a chance that one turbo only has surge ?

What could be the reason of turbo surge? My BRVs are with piston and spring, I think they cannot fail. Shall I start by changing those?

Thx
Antonis