buzzing sounds while deceletrating
 

So I just got a 2010 (last week) and it came with a Stillen exhaust, nothing else. By the looks of the way it sits, flush with the bumper, it was professionally done. Anyway...I really like the sound of the Stillen, it would've been the one I put on anyway so it worked out but I've noticed a loud buzzing sound while decelerating in the lower gears. I really noticed it while city driving, having the sound echo off the buildings. Is this a normal thing with these exhausts or could it be a leak or something else?

Sounds like it's vibrating against the rear crossmember. Either drop the crossmember with some washers or try to adjust the exhaust.

If its more of a SWOOOOSSHHH sound then thats normal from our engines under deceleration.

Thanks for the responses...I will have to wait until I can get to a garage to check....really don't feel like jacking it up on the street...lol. I'll let you know how it goes.

Check the heat shields on the underfloor (between the exhaust and the floor pan). These are usually pretty flimsy and can be bent fairly easily if you are not careful. These will create a nasty buzz/rattle.

Ive been really noticing this. I have HFC's, ypipe and exhaust and it sounds like a blow off valve when i let go of the gas. Why does it do this?

HFCs can make that noise, but shouldn't really do it on decel, that's usually an exhaust leak.

OP, check the evap canister shield near the rear mufflers, that normally should be removed with most after market systems as they vibrate against it.

This was definitely true for me. It gets worse the hotter they are. Mine would rattle at takeoff, at certain RPM's, and then constantly at freeway cruising speeds when it's hot. I took a bottle opener and stuck it between the body and heat shield and started prying it up some, it didn't need much.

I get that too. Best way to describe it is like a really loud aerosol can spraying.

i get that on decel and hard accel, its the HFCs that do it. i need resonated ones.

I've got resonated 18" and it still does it.

i got 12" res but i dont have resonated HFCs. do you have resonated HFCs?

Yes, resonated HFC's.

someone was telling me this weekend that the flexible parts on the ypipe might also be making that noise because they are weak and they break. Or maybe its a blown exhaust gasket, but if you all say its the HFC's, then maybe I have nothing to worry about.

It's the HFC's.... It's normal.... check around the forum.

But what is it? Just curious...

So I finally got Nissan to take a look at it since I bought it there a couple weeks ago and it looks like it was the exhaust hitting the crossmember. They obviously wouldn't dare touch the "structure" of the car so I will have to take it somewhere else or get ambitious myself. Thanks for all the responses. Anyone know what size washers or how many to use? Also, while I was under the car, I noticed I have HFC's. Can someone help me determine what kind they are?