I’m getting ready to build a new complete exhaust for my turbo car. Right now, I think it doesn’t sound too good. Currently I have a single 3” with a borla pro-xs muffler in the middle of the car, obviously not far from the engine. I’m going to build my own dual mode muffler and I can put it up front or in the rear. I’m going with 3.5” all the way from the turbo, out there back. The new Camaros have mufflers in the rear. Vettes, rear. G8’s in the rear and they have a better sound than my car. It’s not because of the turbo, it was the same when it was naturally aspirated. Just a little quieter now. And no drone. So should I do a muffler in the rear this time? I still want the car quiet when the cutout is closed, and I worry that killing the sound in the rear of the car instead of the front will allow more “rumble” inside of the car. Thoughts?

 

I think in the rear would be best. This way the exhaust cools a bit (but how much??) before hitting the muffler, thereby also quieting it a bit. My theory.... lol

 

Muffler in the back, cutout as far up as you can fit it.

 

see that’s the problem I have. I’ve got an expensive cutout and it still leaks. I hate hate hate the way it sounds exiting under the car and it rattles my whole car. That’s the point of me building a muffler. High flow exhaust out the back, probably make the same power through the muffler vs wide open, but when I want it to sound roundly it will reroute though the open straight through side of the muffler.

 

You could do both. Get a cheap and longest you can fit dynomax 3.5 in the middle and whatever you want at the rear. You could even go with a 3.5 reverse flow turbo muffler for the rear and add a cutout pipe before that muffler for racing. That with the turbo would be very quiet.

Spintech has the best sounding muffler in my opinion, a 3.5" sportsman in the rear and routed out the back or axle dumped would sound great and an added dynomax in the mid pipe would take a lot of edge off.

There are so many ways you could do it. Texas speed makes a 3.5 catback that has a cutout built in already.

 

I've had a couple spin techs, good quality, they don't have the raspy ring in the shorter ones in the flowmaster series, that being said at WOT they don't take many prisoners,
I am running a flow master 70 (3") on my jeep, its a monster for a rig this size but its a really nice rumble and doesn't seem to do the high pitched rasp at all at higher RPM. 2.5 cats then pipe up front y'd into a 3" that feeds a pipe to the muffler.

The spintech do work harden after a year or so, I added a piece of insulation and another piece of stainless sheet metal on the top and bottom with long stainless hose clamps to sandwich the muffler, toned down things a fair bit. I'm considering doing to to my flowmaster just because..

 

I've had good luck putting high temp rtv against the mating surface that the cutout valve seats against to help with any rattling. Have to add some more over time but it works for awhile.

 

I don’t think an F body exhaust will fit my gto.

 

for whatever reason reason reading it as if it was a camaro. Same advise applies but for mufflers. How much room for a muffler do we have to work with?

 

heres some pics

 

And look, I did the best I could building that exhaust with me on the ground laying in my back and the car on jackstands. It was supposed to be temporary, first complete exhaust system I ever built. The next one should look much better.

 

Dude! It is WAY better than I could do! LOL I'm challenged by the kits in a box!
That actually looks like it should flow well.
Isn't the OEM muffler in the rear anyway? Might be wrong on that....

 

I always use a resonator up front in the middle (behind the X pipe for dual systems), and a muffler in the back. Usually, if more sound is sometimes desired, or more flow at low vacuum (high boost), I run a "Y pipe" to split the exhaust after the resonator, before the mufffler. Run the second pipe to very near the exit point/tip for the cutout pipe, and use a cutout valve on a flange right at the exit. The closed pipe acts as another resonator when the cutout valve is closed, and obviously as another unrestricted exit point when the cutout valve is opened.

 

Heimholz chamber....

 

Okay and to be clear you are looking for good flow and better sound but not necessarily louder or quieter?

I would do a spintech 3000f 3.5" where the Borla sits and get a 3.5 glass pack or full size borla/dyno/mag that will fit in the rear that you can make removable and replaceable with a straight pipe if you want less bite. No cutouts to deal with.

Spintechs sound great on LS cars. I have true duals with 9000s and it is very loud but not obnoxious. Doesn't have that blatty/bass intensive sound. It is very much chambered in sound quality and has a little bit of burble on decel. Although it does sound different vs a Flowmaster. You can tell a difference.

 

I'd leave that muffler where you have it and add a 2nd small one on the OEM location at the bumper. Then add the cutout right where the exhaust is near the crossover.

 

thats exactly how it is right now. I wasn’t getting notifications to my email I guess. Didn’t see these last few posts.

I’m going to carry on with my original plan. I’m all caught up on transmission building so I can get back to the car soon.

3.5” from downpipe to muffler, split to dual 3” at the muffler. Build a dual in/out muffler. Cutout on the straight through side. It’ll merge back after the muffler. The reason for the dual in out muffler is it’ll add volume to the muffler case. I want it really quiet when the cutout is closed.