I just had my ASP Pulley kit installed a few days ago and yesterday was beautiful here in NJ (60 degrees!). So I did some driving around with the windows cracked. Because of this it allowed me to pick up on a sound I haven't noticed before. I'll do my best to explain it:

- it's a sort of super high pitched squeaking/squealing noise but it's very feint and easily drown by wind/road/engine noise however if you in tune with what sounds you USED to hearing you can hear it (ps My wife couldn't)

- it only comes on when I'm inputing a moderate amount of throttle, and seems to start around 1700 rpms and fade out at 2300-2500

- when accelerating slowly and it shifts which drop the rpms into that range I hear it as well (ie I hear it when I pass that rpm range in first gear and even when the tach drops into that range after a shift)

- If I'm careful and keep the throttle around those rpms I hear it consistently. As soon at the rpms drop below, or raise above it disappears.

Anyone have ANY idea what this could be? I hope I described it correctly- it's not loud at all. If it were I'd be even more worried. It's one of those things I'd probably hear best if I was driving with my window down near a building/wall.

Thanks in advance everyone!!!

 

Im going to say its one of two things.... possibly the S/C clutch engaging (normal), or just phantom sound from the pressure differential in the NW CAI. From what you described I have the same sound... and if I remove my NW CAI, the sound goes away.

 

Great- thanks for the speedy repsonse! So you hear the same thing? That makes me happy to know I'm not crazy! It's one of those sounds it's so feint most won't pick up on it but it's most definitely there and most definitely RPM dependent. Have you noticed that?

 

crosshair!!! that's what a supercharger sounds like!!!! the sound of it resonates through the metal tubing in the CAI, and the pulley kit is winding it up faster

i LOVE that sound! supercharger whine!

 

Trust me I love the supercharger whine too- unfortunately it's not that sound.

 

i see.
could it be leaky gaskets? losing pressure? do you have the NW cork gaskets?

 

Does it sounds anything like this?

http://www.youtube.com/watch?v=K21qpVmwHO4

 

Now THATS sc whine. Again mine is a different sound- very feint, and ONLY when using moderate throttle. Heavy throttle would cause the supercharger to spool up drowning out this sound with it's own.

 

I noticed a very faint high pitched sound before the idler pulley bearing went south.
Might want to check that out as well.

(Suprisingly it did not fail at high rpms)

 

The idler pulley was replaced I believe, w/ the one from the ASP 178 kit. How do you check it out? What do I look for?

When you started hearing that high pitched sound when did you hear it, at idle or at a certain rpm like me?

PS It won't make that noise in Park regardless of RPM, only: 1. While in drive 2. With moderate throttle input and 3. Between the aforementioned rpm ranges.

 

Thats exactly what I was describing as well.... if you have a stock air box to toss on, The sound may go away. I honestly think it has something to do with part throttle boost passing by the throttle actuator and the NW CAI.

 

Very possible that it is just an Harmonic oscillation!

 

Just installed my NW-style CAI and I immediately noticed this sound you are referring to. Mainly after 2K rpm or so.

It is a sound I will gladly get used to! It's great to hear that SC

 

Oscillation is a great word to describe the sound the NW mani's make. You can hear that air moving. That's why mine is so loud between the two mods the whine is a combo of the two mods. I get so much compliments at the track that once I get back to the pits usually there are 3 to 4 guys waiting for me to pop the hood. I have lots tell me that my turbo is really loud.

 

If it's indeed the SC why does it only come on at 1700rpms and disappear around 2500, and is only audible with very moderate pedal input (ie accelerating slow and steady, NOT flooring it).

 

I heard mine at steady highway speed, only at that speed nothing at idle and nothing at higher rpms.
Clearly not a whine of the SC in my case.
If I had to describe it - it had an almost electronic pitch - I thought something like the radio was going bad.

If the installer over-tightend the idler you could have this issue - that is what was causing several of the bearing failures. (At least, that was one of possible causes of bearing failure)

Maybe you are lucky and it is the intake.

 

Do you know what the torque spec is on the idler pulley?

 

LET instruction states 13-18 ft lbs (18-24 Nm)
I would also use a bit of blue locktite

 

Maybe you have the SC clutch chirp that the E55's experience. Some of theirs make a loud sound when the clutch engages and disengages. You might be able to find a clip on youtube. It was a common theme with them.