I'd like to add a resonator to my system to reduce the noise level. My current noise maker: LT1 engine, SLP 1.75 shorties and Y-pipe, Magnaflow 3" cat, Edelbrock 3" cat back SDT (dual 2.5" outlets).

I think there is a spot for a 12" long x 4" OD resonator under the back seat. Has anybody tried this already?

 

FYI: My quieter 3 inch exhaust. I have added a pair of Summit Racing 2.5" inlet/outlet 12" glass pack bullet mufflers in place of the 2.5" tailpipes. They made significant difference that even my wife noticed immediately without having heard the car run since the day before. Despite the audio in the linked video, the exhaust has lower bass tone now without the loud droning rattle.

First in the video is the original Edelbrock RPM exhaust, then with bullet mufflers in place as pictured below.
http://www.youtube.com/watch?v=Z5683ljboqA

 

kewl!

 

if you want to stay with a 3 inch flow why dont you put either a resenator or chambered exhaust as part of the mid pipe between the cat and the rear end. just cut out a piece and put it in. you can get a 3 1/2 inch external chamber exhaust with a 3 inch internal and there is no problem with it fitting. that way you can keep it 3 inches all the way and not increase back pressure droping it down to 2 1/2, or adding bends into the system.

 

That was my first thought. I didn't add any bends, the 90 degree to the pair of 2.5" tailpipes were already there. I didn't reduce anything as the muffler was a 3" inlet with a pair of 2.5" outlets.

I went this route because: If I didn't like the resonator, I would have hacked up an expensive mid-pipe for nothing. A resonator in the mid-pipe would have cut down on my ground clearance (car is lowered). It would introduced a restriction in an otherwise smooth straight area of 3" (7.07 sq-inch area) fast flow section of pipe. You always want mufflers and resonators as close to the exit as possible. The glasspacks are mounted in a pair of 2.5" (9.81 sq-inch total area) fed from the single 3" muffler inlet. This way was destined to be louder and slightly more expensive than the resonator, but my opinion is that what I did is less restrictive.