[BigDaddyEureka]

So I had the opportunity to take Scarlet out of a quick run and had something odd happen. I was feathering out the throttle from full thrust to line up for a high speed corner and heard a weird, loud, high pitched scream. As soon as I feathered the throttle back in it went away.

Tried to reproduce it several times but no biscuit. I'm almost wondering if it was the passenger window howling from the airflow, like maybe it wasn't all the way up?

I listened to this thread's videos of supercharger issues and don't hear anything like that. I'm thinking it was either the window with a tiny leak or maybe the secondary throttle under the s/c snout bleeding some boost off.

I'd post a recording but just couldn't get it to happen again. Anyone ever heard something like that?

 

[BigDaddyEureka]

On that secondary throttle idea, the M6 folks would here that more often than I do with an A8. Basically if you at a full boost and drop the throttle to punch the clutch in, the secondary throttle opens to bleed the boost off so you don't frag the blower.

 

[Xylander]

A scream? Belt slip?

 

[BigDaddyEureka]

A scream? Belt slip?

Maybe, but it sounded more shrill? Like an almost metallic component to the noise. I didn't see anything that looked like a belt slip, but it might be a good idea to mark the belt relative to one of the pulleys or something...

 

[16GoManGoHC]

So I had the opportunity to take Scarlet out of a quick run and had something odd happen. I was feathering out the throttle from full thrust to line up for a high speed corner and heard a weird, loud, high pitched scream. As soon as I feathered the throttle back in it went away.

Tried to reproduce it several times but no biscuit. I'm almost wondering if it was the passenger window howling from the airflow, like maybe it wasn't all the way up?

I listened to this thread's videos of supercharger issues and don't hear anything like that. I'm thinking it was either the window with a tiny leak or maybe the secondary throttle under the s/c snout bleeding some boost off.

I'd post a recording but just couldn't get it to happen again. Anyone ever heard something like that?

How fast where you going?

 

[16GoManGoHC]

Did it sound like this?

 

[BigDaddyEureka]

Did it sound like this?

YES! That's the !#%^ sound!

Thanks so much for the video - now I know where to start looking to fix it!

It also explains why when I rolled the windows down and back up to try to listen for it the sound went away. I probably got the window resealed when it went back up.

 

[16GoManGoHC]

YES! That's the !#%^ sound!

Thanks so much for the video - now I know where to start looking to fix it!

It also explains why when I rolled the windows down and back up to try to listen for it the sound went away. I probably got the window resealed when it went back up.

It happens mostly when the vents are set to outside air and the interior at speeds say over 100 or so the pressure inside the car greatly exceeds outside and literally blows the windows out to escape. Try driving with the vent in recirculate and you most likely won’t hear it then.

 

[BigDaddyEureka]

Good point @16GoManGoHC - I think I did have the vents running because the A/C was off since it was nice out for the first time in weeks. I'll keep the recirc trick in mind for next time!