buzzing noise from exhaust - turbo?

[jt1583]

After I got my car dyno'd, my car was making a strange "buzzing" noise that from inside the car sounded very much like it was coming from the rear exhaust / muffler area. I thought it was definitely turbo related, my guess was the impeller blades were contacting the housings, mainly the turbine blade/housing.

Well I replaced the turbo, with an SR T25 that to me felt like it had slim-none shaft play and I couldn't see these blades contacting the housings. However when I got my CA T25 off it wasn't in that bad of shape either...
Long story short, I replaced the turbo last night and today it feels like it is making about the same noise. A distinct buzzing that to the best of my knowledge sounds like its coming from the muffler area. I had the car jacked up on one side and idling and I could hear it from underneath, but was unable to pin point it. I tried sticking a screwdriver to the exhaust, turbo, manifold etc and listening closer but no luck.

These are the conditions it makes the noise
-Slight engine braking
-Slight acceleration (around 0 pressure)
-Constant throttle acceleration

I'm starting to think that it's not turbo related. What are the chances that both T25's I've had on there make almsot the exact same noise? Maybe I shot something into the muffler? My next step is to remove the cat or downpipe and see how the sound is effected.

Any input appreciated.

[LA_phantom_240]

Make sure the exhaust isn't rattling against anything.

[clark]

if your impellers were contacting the housings, you'd here scraping/screeching, not buzzing.

it sounds like you either have an exhaust leak or rattle. make sure the exhaust isn't contacting your chassis/suspension.

jack it up and start moving your exhaust piping around, check your flanges for leaks

[mifesto]

maybe your hangers are sagging and you need new ones as the exhaust is making contact with something....

yeah its definitely not your turbo, if the impellers are hitting the housing it means your turbos blown and you wont be making much boost at all(and u'll be getting a terrible exhaust smoke when u get on it)

[los_inc]

make sure your not hitting your tow hook
-los