Turbo 98 cobra fluttering noise... need help

[98cobra#1222]

Trying to figure out what this fluttering noise I get from 2000 rpm to 2700 rpm and about 1/4 to 1/2 throttle. It's a fluttering sound that I thought was an exhaust leak but after pressurizing the exhaust and spraying all the v bands with windex I couldn't find any leaks. Has anyone hear a similar sound or have any suggestions of what to try out. Hoping to get it squared away before the car gets tuned in a couple of weeks.


[video]https://youtu.be/U87lMMAbaJc[/video]

 

[Sonic605hp]

I can't hear what you're talking about in the video.

 

[byeofcr]

Throw out bearing be my guess

 

[98cobra#1222]

I can't hear what you're talking about in the video.

Damn it's really hard to pick up in the video. I'll try to get a better video. In this video if you hear the turbo spool the sound is there just before that, almost sounds more like an air leak than the fluttering sound it makes in person. Perhaps my camera is aliasing the frequency of the sound. You can somewhat make it out when the boost gauge goes above 10 inHg, there isn't any noise at 10 but it starts just above that around 8 inhg.

Throw out bearing be my guess

Would it be load dependent? I would think the throw out bearing would make noise regardless of load. Is there anyway I could test it without dropping the trans lol


Sent from my iPhone using Tapatalk

 

[crazycarlo]

Have you checked your wastegate to make sure it's opening and the sound isn't compressor surge?

 

[98cobra#1222]

Have you checked your wastegate to make sure it's opening and the sound isn't compressor surge?

No I haven't, but this is running the car up to atmospheric pressure so the wastegates should both be closed the entire time. I also wouldn't think the compressor would surge with the throttle open since it would be operating a good distance from the surge line.

 

[98cobra#1222]

Here is a better video of the sound. I've checked all the gaskets and just have a very small leak on the header gaskets. All the v bands are leak free. [video]https://youtu.be/Q4PZgmfjmmw[/video]