peadya100 wrote:Nah its not happening on boost, its happening at 1500-2000rpm.
at the point right before boost come one.. like 0-1psi on medium throttle..?
If so i had two causes of this noise on my GT Fozz.
1) Wastegate chatter.
-with a big dump pipe and factory boost control (that still allows some boost pressure to get to the WG actuator at all times) there is very little exhaust restriction compared to the stock dump which allows the wastegate to just creep open a tiny bit and chatter against the exhaust housing, very common problem on TD04 equipped cars. solution was just to pre-tension the WG actuator arm a turn or two
2) Compressor Surge
-this is the turbo being able to produce more airflow than the engine can consume with only a partially opened throttle.
Common on just about every factory turbo'd subie, but you usually don;t hear it with a stock intake and exhaust.
if you de-restrict the intake and exhaust, it makes the problem worse, doesn't usually cause any drivability or mechanical issues, just a funny nose as teh turbo reaches 0-2 psi
pssssss chchchchch psssss
otherwise it could just be a rattling heat shield.