So, I have had a couple different systems on my '94 formula and the current system has seen mulitple configurations. The interior noise level is not good. The motor is still the stock long-block with bolt-ons, Crane gold RRs, and the LT4 Hot cam. Headers are SLP 1 3/4 stainless mid-length.

What is on the car now:
SLP y-pipe terminating at a 3-bolt flange
Random Tech cat
Flowmaster American Thunder I-pipe
Flowmaster 50-series deltaflow single 3" in/out
3.5" mandrel-bent tail pipe (looks similar to a Mufflex hidden setup)

Just before this I had a cutout in the I-pipe that we removed and welded in 3" tubing ensuring the inside of the pipe would remain smooth. I think the cutout was working as some sort of baffle. I do not believe that just adding the 3.5" tail pipe over the 3" would result in such a drastic increase in volume.

We also had to splice in a piece just before the muffler to combat some corrosion. The piece spliced in was from a 3" mandrel bend. I have been using 3-bolt flanged for he i-pipe to muffler connection for a long time and we used that same setup again.

This particular 50-series deltaflow has been on the car for about 4 years now. It's in great shape.

The previous tailpipe was a single 3" mandrel-bent piece that extended more our from under the car and down a little.

The previous setup wasn't too lound inside the car and gave a good exhaust note.

The new one is making it hard for me to hear my kids talk at certain speeds. The exit of the muffler was opened to 3.5" before the tailpipe was welded. I still use the factory exhaust hangers to keep vibrations down.

What can I do to tame this thing down without spending a lot of money....? I really like the muffler and even with the increased noise (it isn't really resonance...the car is louder) it still isn't as bad as the 80-series, dual exit the system came as many years ago.

Since the rear of these cars are really low on sound deadening in the rear compartment, would some dynamat in the rear well, the shelf, and wheelwell areas keep that sound down...?

Again, the sound quality of the exhaust is great, but the interior volume at certain ranges is not good. At highway speeds the noise is fine. But at any speed the converter isn't locked up the car is just too loud inside for me to hear the kids. Living out in the sticks as we do, a lot of our driving is 45mph and less (narrow roads, 35mph limit, lots of DEER).

Thanks for you suggestions.

 

i dont mean to come off as an a-hole but i hate when people complain that there cars are too loud. i have to kinda think.. just run a factory exhaust or deal with the noise.

best i can think of, keep your cats, and get a hooker cb.. from what i know there very quiet till your on the gas.

 

Don't worry about it. You came off that way.

I'll ask the admin to delete my thread and I'll go find someone else to give me some ideas.

 

You could try adding some more sound deadening material as it is thin or nonexistent in some areas. Another thought may just be your catback, the Flowmaster is kind of throaty. My Magnaflow is very tame and I haven't had any problems with resonance either, but it opens up when you have your foot to the floor which is when it counts I guess. Sound deadening material would probably be your safe and cheaper bet to try first.

 

As mentioned. I would try to put in some sound deadening material. But I am kind of wondering your reasons for putting an aftermarket exhaust onto your car.

 

either go back to stock or get a magnaflow. i have one. not very loud but gets louder at WOT. it has a nice sound without any resonance

 

Why...? The car is my only tranportation to/from work and my only 'toy'. Without exhaust it wouldn't run 12s or be able to kill cones on the autox as well as it has. It also wouldn't be nearly as much fun to drive daily.

Maybe you all don't have young kids that ride with you in your f-bodies.

The sound itself is fine. The interior noise level has rose to a level I can't hear my sons well at anything more than cruise rpm or decel. A good grade will even make it hard to hear them talk. They don't mind much and when we're 'playing' in the car they really like it, but I want to be able to hear them talk.

I'll give the sound mat material a shot. I think most of the noise is coming through the rear well and shelf area (according to my eldest).

I don't ride in the back seat of my car, but I am going to get someone else to drive it so I can see what it is like for them. If the noise level is too bothersome and they jsut aren't complaining about it I may have to take more drastic measures.

I want them to continue liking cars, racing, etc and not be annoyed by it.

I suppose a good indicator is if they ever stop asking to ride in 'daddy's car' instead of 'mommy's truck'.

thanks for the input.

 

like everyone else said, the magnaflow is very quiet. also, do you tips completely exit out of the rear? when i had tips on that were a little too short, it resonated very bad through the hatch.

 

yeah, the tail pipe ended up shorter than I had planned and I suspect that contributed most of the increase in sound level. About 6" of 3.5" tubing should help get more noise out from under the car.

thanks.

 

very good point. i noticed a big difference when i put on my magnaflow catback. i cut the tips off that came with it and didnt put anything on it and it resonated very bad and stuff vibrated. sounded different. i then added some pipes and exhaust tips out the back and it changed the way it sounded for the better. no more resonance and vibration.

 

If all else fails. Maybe put some sort of a high flow muffler somwhere in the middle of the set up along with what you already got on, like a dynomax bullet or somthing of the like. I've seen a few set ups where people have done this.

 

I did my whole trunk with Dynamat after I installed the fuel pump with the "trap door method". I covered everything but the inner parts of the rear quarter panels. It made a BIG difference driving with the top up.

I buy the dynamat off of ebay, just do a search on "dynamat extreme bulk" and then compare shipping costs to figure out who is cheapest.

You might as well do the door panels while your at it too to help cut down on the road noise. I like to do the inside of the door skin itself, then another layer just under the door panel.

I used some of this in 1/4" over the dynamat in my roadmasters doors FWIW.
http://www.closedcellfoams.com/neoprene.html

 

yeah, I think the dynamat is the best bet for now and then I'll retool the tailpipe to be a little longer to get the sound outside the car more.

thanks for the response.