This noise is driving me nuts!!!

[ttz91]

I posted this on another forum and got no response.
"I have a strange noise when building boost. First you hear the turbo begin to spool then a very loud fluttering sound then the turbo spool again. I thought it was a boost leak that might be sealing itself off when it got under more boost (10-15psi). When I did a leak check the only place leaking any air was the bottom rear of the passenger side valve cover. PCV's are new also. Does anyone think that a valve cover leak might cause this. I am going to change it anyway but wanted some input anyways."

I don't think it is detonation because it goes away at higher boost. I have also tried octane booster with 93 octane gas.

[TC]

recirc valves?

[ttz91]

Sorry I forgot to mention I thought the same thing and replaced them with BOV's and it still make the same noise. The BOV's although cheapies seem to work fine, they only release or make any sound till above 5000rpm or so.

[ttz91]

I even went back just now and plugged the vaccum lines going to the BOV's just to see if they were prematurly opening and the fluttering is still there aroung 3000rpm-4000rpm then it goes away.

[Zeorymer]

you are hearing compressor surge from your turbos... :(

[ttz91]

I don't think it is compressor surge because it is only when accelerating. I think it may be a tiny exhaust leak at the rear of the test pipes. When I tore everything down to do Subframe bushings and clutch replacment the rear gaskets look like they may have been leaking in several tiny spots but not blown out. I will find out when I get it all back together.