compressor surge? leaky BOV? slipping clutch?? boost leak??

[jmakado]

alright, here it goes. i'll do my best to explain the problem. it started about a week ago. if i am driving on the highway in fifth gear at say 2500rpm's and floor it, i get boost up to around 15psi at 2800-3200rpm's and then a big "flutter" in the boost like 14-15-13-15-14-15 etc. it is also acompanied by a "buffering" sound (like when both rear windows are down in a car but both front windows are up) and a jerking back and forth from the car to the point that i have to let off the gas. if the car is under more load, like going uphill, then a really loud "chirping" is heard instead of the buffering and the jerking is even more violent. if i floor it and get to 10psi and then abruptly let off the gas the BOV sound is accompanied with a loud chirp.......now, just to complicate it more. it only happens in fifth gear and sometimes in forth but only at low rpm (under 3500). it has happend with both 91 and 104 octaine in it. my car is running awesome other that. i was at bandi last night and ran a new best with the 16g. 13.90@98mph with 1.8 60's. here are my mods that are important:
2gAWD, 16g, 1g bov, stock clutch with 80K miles, all hard intercooler piping, joe p mbc.....i tried to log it happening but it didn't show much. one other thing, it will randomely jump to 18psi in fifth but holds rock steady at 16psi in every other gear??? any help would be grrrrrreat!!!

[ImolaFem]

Did you test for boost leaks and do you recirculate your BOV into the intake?

[jmakado]

i do recirculate into the intake. i haven't tested for boost leaks yet, but i don't seem to have any problems holding boost. i also think that it would show up in other gears....i am starting to think it is clutch more and more. i am now hearing a sound like pigeons(soft fluttering) when i engage my clutch.

[Danny]

Sounds like crank walk.

Actually your description is in depth but still kind of vague. That was contradictive but oh well. What is fluttering the clutch or the BOV?

[ImolaFem]

"holding boost" at 15 psi isn't hard. Even if you have a boost leak. The turbo will just work harder to hold that 15 psi. Do a boost leak check and get back to us.

[jmakado]

Just thought I would post a follow up as someone may find it searching in the future.
The problem was comp. surge. After doing some simple math it looked like I was ending up to the *left* of the comp. map. I found that at such high PR's ( from our altitude) the engine wasn't flowing enough air and the turbo was surging....This was all just in theory and on paper until recently when I switched to an E16g which has the surge line pushed much further to the right and is capable of higher PR's.
So, the problem has gone away with the new turbo. It's nice to be able to floor it in 4th/5th now without having to drive around the surge.
The morral of the story:
I think that the small 16g is a great daily driver turbo but is not the best choice for our altitude much like the B28 (for different reasons).
The e16g also spools quicker and is kick ass.....but that's another thread.
One last thing, I just wanted to thank HotRod for his many e-mails and help with the math on altitude adjusted comp. map reading.

[Van]

If I'd have seen this before, I'd have told you it was surge. You just needed to downshift to get around it, but it's better that you changed the setup for your driving style. Just flooring it in 4th or 5th under 3500 rpm could make alot of turbos surge. That stuff is better left for N/A V8's. ;)