Not sure what you mean by a wastegate?!?! I definately feel its something with air flow, just from the sound. I will pay more attention to it when the car is cool and then warmed up...

 

if you lowered it, and dragged the cat, you may have broken a spot weld on the heat shield. when the metal heats up and expands, it might be pushed into a position that constrains the shield so that it no longer rattles.

depending on whether the shield is still in a "safe" position or not, it probably shouldn't be a problem- only an annoyance. OTOH, if it's dangling and no longer "shielding" the cat, you might want to take it to a muffler shop and have it re-spot welded. due to your lowering the car and dragging the cat, i doubt any dealer would cover it under warranty.

 

what people are calling a "wastegate" sound may actualy be an AIV (would say EGRV but if it only does it when cold I'm leaning towards air injection).

Normally aspirated cars do not have wastegates... i know everyone knows that- just stating the obvious.

 

Yep, as others have said, this isn't the smoothest or quietest engine in the world. One of the best WRT HP and torque tho.

 

I guess I need to get the car up on some jackstands and take a look at it. I will see if it always does it or just when cold as well...

 

That's exactly it, punch it to 5-6K, then let off the gas and you hear it. it's very hard to describe, slightly hollowish sound, like you said, a rattle but not a rattle if that makes sense.

It's gone before I can even really listen to it good, it seems to be just for the first few minutes of car warm up. I'm not at all concerned with the noise, just curious as to the reason for it.

 

hmmm. if that's happening to everyone then it might not be a heat shield.

that could be the IAC (idle air control) Valve. They tend to go wacky right after the throttle is closed after WOT and high RPM. over the last five years or so, emissions have required that IACV's go a little nutso after WOT to reduce unburned fuel from being dumped into the cats unnecessarily (the air fuel burns before reaching the cat due to false throttle input)

 

BTW, if you've driven a late model BMW (they do it A LOT) stickshift and the revs rise or "hold" between hard shifts, it's because of this new IACV tuning.

i hate it.

 

This could be kinda like the stupid SET Valves on the newer model sport bikes. It was used to regulate exhaust back pressure and limit unburned fuel making it out the pipes etc etc. It was the first thing I ripped off my new Gixxer. It made a big difference on the bike... the throttle response got so much smoother and the exhaust note wasnt choked-

 

Sounds like you have the same thing going on... thats good news. I might still take a look under it sometime when I get a chance. I have to finish unpacking though first, moving SUCKS!

 

sort of. SET valves as you said are on the exhaust side. IACV is intake side.

 

....and i've heard only good things about those valves on the new gixxers... does it really not work well??

 

No one seems to like them, yanking it smoothed mine out ALOT, sounds better too, its not so restricted. Go to www.gixxer.com and search set valve. You will see a lot of threads about removal and the like-

 

I am thinking (and maybe kring) could back this up, it sounds like its coming from just behind me (while sitting the drivers seat). This would tend to make me believe its more exhaust related than intake?!?!

 

sounds can do weird things in enclosed spaces....