reducing drone
 

is drone caused by the vibration in the pipes? If so would adding some hangers at various points help in reducing vibration (drone)? Love my FI but want to calm the drone down some while at 2K. I love the note when jumping on it and starting/idleing the car.

I have the 7AT w 12s, anyone have an AT with 18s? If so hows your drone?

Do you have just the exhaust or hfc too?

A lot of systems have a natural resonance at certain RPM's on certain cars. Not too much you can do at the exhaust level without major surgery, but sound deadening the car can reduce the annoyance..

Adding sound deadening to the interior of the car is the only real option. Be advised it is going to take a significant amount of quality mass-loaded volume to be able to block the drone and you are going to end up adding, at minimum, 50 lbs to the car.

Applying it to the hatch alone won't do much because there is no deadening in the rest of the car so it just finds other ways to get through... you'd have to do the whole floor and hatch to make a noticeable impact.

Since you have the 12" resonators you might want to consider swapping for the 18". You'd probably be able to resell your 12" so you might not take that much of a hit.

I have the 18" and the only real annoyance is with highway driving if I need to be applying throttle. Flat roads are fine, but throw some hills and mountains in there and you are constantly dealing with that noise. Everywhere else I think the sound levels are fine.

You're killing me, Steve!!!

The drone, I would guess, is caused my the lower volume of air going through the exhaust. Increase air flow -> increased tone/volume of exhaust. The resonators are there, I believe, to reduce that drone, at the cost of upper-RPM goodness. The 18" resonators won't be as loud and deep as non-resonated, but drone will be worse. You should be right in the middle with 12" resonators.

My belief is that in order to get your ideal tone at 4-6k RPM, you have to be ready for the 2k RPM "drone".

None of this is fact or professional opinion, btw. If you have any issues, I'll gladly take the exhaust off your hands!

Hmmm. I seem to remember Tony very clearly stating that the resonators were only there for sound control and that the only difference between non-res, 12, and 18, was the volume.

The treatment depends on if the drone you hear is structural or airborne noise related. If structural, adding damping at the attach points of the exhaust would help minimize the energy getting into the structure. If airborne then the mass addition to the interior panels is the way to go only after identifying which panels are the greatest contributors. If most of the airborne noise is vibrating your windows you are pretty much screwed unless you can change the modal characteristics of the window ("add a heavy tint layer"......joking).

Notice all the "ifs". Careful effort identifying the "source-path-reciever" will enable the least amount of weight addition.

You gained HP why throw some of that goodness away by adding unnecessary weight?

My Corvette had a big plastic tub sitting right over the Mufflers. After installing headers and HFC's I had an issue. It resonated like a Bass drum. On Vette's the drone RPM is 16-1800 RPM's which is easy to work around with the next lowest gear selection. Regardless, a liberal coat of Second Skin Damplifier helped quite a bit. Maybe 25-30 lbs worth. Some Z guys have done this...Check over in the Audio section.

http://images33.fotki.com/v1119/phot...MG_2161-vi.jpg

http://images33.fotki.com/v1120/phot...MG_2159-vi.jpg

is that how bad the drone is for the FI exhaust, i thought everybody was all saying that there wasn't drone, i guess you can't trust everybody's reviews on it

Yee-Haaawwww!! Let's have a bar-b-que!! Looks like you can throw the chicken right on top of that foil!

(sorry)

When I was shopping for CBEs, my intuition was that the FI droned but owners weren't admitting it. A few guys slowly began to say things like "it's a little loud at 2k rpm but you might not care." That was enough for me to realize the hype of waiting and then finally receiving their exhaust meant they couldn't bring themselves to say anything negative about it. I do love the way the FI exhaust sounds in the videos, but there's drone. Even Tony says in his video "very little drone, if any at all" which to mean translates into "some drone but I don't want to say no drone cus I'd be deceiving". Still loving my Stillen CBE.

I have been the most vocal about it and have caught a lot of flack for it from many of the FI guys. Oh well... just trying to help the community.

Anyways, Modshack, that's what I did... a coating of damplifier topped with Luxury Liner Pro in the hatch. It made a small difference but I'd need to do the entire car to be most effective. I did get rid of some hatch rattles, though, so that was nice. :)

Look at it this way - you're making those of us who went with Stillen feel better about it :rolleyes:

I wouldn't trust anyone's review here. Hate to say it, but more than a few here think mind numbing drone and alarm triggering noise levels are the Cat's meow..
I watched the Corvette guys cycle through 3, 4 or 5 different exhausts (at $1000 a crack) based on "Reviews" until they found one they liked. I suspect we'd have more of this here if Z owners had the Mod money the Vette guys do

My fear with Stillen, and potentially the future Berk CBE, is that it won't be loud enough. If I have to deal with a little drone to get the tone of the FI, so be it.

How aggressive is the stillen? From the look of the muffler design, I wouldn't guess it's too loud at all, just a little throatier than stock.

I'm looking hard at FI and Berk right now.