My turbo sounds like it has a stammer

I recently had a few upgrades installed:

 

GS Uppipe

Cobb Downpipe

Cobb Stage 2 Map

 

I expected a bit of a different sound, but what I've got sounds rather odd. There is more turbo whistle audible, but there's a stammer/stutter to the whistle. Kind of like if you were whistling and vibrating your tongue simultaneously. The stutter is tied to engine RPM, not to road speed, and is only audible when the turbo whistle is audible. I hear it most clearly while accelerating gently in first and second gears.

 

Seems to be audible only, power delivery is smooth. There doesn't seem to be any effect at higher boost levels - although it may still be happening, it's just harder to hear over other engine/exhaust/wind noises under higher load or higher speeds.

 

Normal? Fluttering wastegate? Leaking vacuum connection?

My first guesses are yours--wastegate flutter or loose/leaking vacuum line. Seem like easy things to pinch or only partially reassemble when installing up- and downpipe. Wish I had more advice other than it's probably not the turbo itself. I'd check the vacuum lines and then do the 'ol bubble test on them.

For anyone who's curious, I recorded an mp4 audio file.

 

http://vocaroo.com/i/s1IXg8HkYnNn

Exhaust leak

Video sounds like you are driving through a tunnel, but my turbo makes a similar sounding noise. It started when I swapped to a BNR16G from the stock turbo 3 years ago. I always assumed it was wastegate flutter. Maybe it's actually a small exhaust leak.

 

I'll feel really dumb if that's the case, although I've never noticed any telltale signs of carbon build-up you usually get from exhaust leaks. JmP, where would the leak be most likely to cause this sort of noise?

Back side of the up pipe where it attaches to the turbo. Start the car, wet your hands, and then put them around all of the flanges on the up pipe-turbo end and manifold end, and I'll bet you'll find a leak. Wet hands feel the air immediately.

JmP - I tried wet hands around where the uppipe meets the turbo, but didn't feel any air.

 

Could the leak be between the cylinder head and the exhaust manifold? Is what I'm hearing a "low pressure" exhaust pulse?

 

Thanks!

My car makes a very similar noise when i'm about 1/4 of a quart down on oil.

JmP - I tried wet hands around where the uppipe meets the turbo, but didn't feel any air.

 

Could the leak be between the cylinder head and the exhaust manifold? Is what I'm hearing a "low pressure" exhaust pulse?

 

Thanks!

 

Certainly could be. Also where up pipe bolts to manifold and don't rule out front O2 sensor. It can be bad without setting a CEL and causes all kinds of driveability issues.