Wierd noise on Boost

[Rusty]

Thought I'd open this one up to the forum and see what ideas came up. This has happened since I replaced my turbo with a rebuilt and fettled k24 7000.

When going WOT below 4k5 RPM, I get a hollow whistling noise coming from the car; above 4k5 all is well.

The car needs a mapping session for the new k24 7000 that's on there, so it's entirely possible that it's down to the WGFV reaching a software limit and causing a resonance - should I be able to see this in VAG Com?

I refitted all the EM studs, turbo studs, DP studs, WG studs and replaced all the gaskets. There's no stuttering or boost fluctuation that might indicate a boost leak, although I do need to check for one properly but performance is as it should be IME.

There were some hairline cracks in the EM but they were minor and it's only happening at specific revs and is not high pitched but a bit 'hollow'

It initially sounded like the WG flexi but I've since replaced my gutted flexi (been on the car since I bought it and wasn't identified till this year!). All in all, very wierd and I'd like to find out what it is, so that I don't go to get it mapped and end up not being able to do so because of another issue.

All ideas gratefully received

[QuattroFever]

hmmmmm steady and constant like a whistle but deeper? or more of a flutter? I had some loose wastegate bolts a while back that made a chuka-chuka-chuka noise when on boost. like blowing a whistle that the ball still clatters but no whistle I guess a cracked em would make a similar noise.

[Rusty]

Yeah, it's definately a flutter. The OE setup fluttered a bit around the same revs but this is worse still and has a woodwind note to it! Looking at the boost gauge, all is well with the boost being stable. More than likely something WG related or N75, so just have to get it checked before mapping...

[Billman]

there was a thread for a flutter sound produced when the wastegate pipe (wellrohr) is installed backwards. There is an arrow pointing the right install direction.

[epic]

Thats exactly what I think it might be as well. JP had this on his car after a certain person :corey: did some exhaust work for him a few years ago

there was a thread for a flutter sound produced when the wastegate pipe (wellrohr) is installed backwards. There is an arrow pointing the right install direction.

[Rusty]

I've already thought of that and changed the pipe and fitted it correctly. No difference Will double check though, in case I've been a bit blonde.