One of the non negotiable requirements for my car is a quiet exhaust. Since I'll be running a GN V6 for a while getting rid of the annoying V6 sound is even more of an issue.

My initial plan is to run a 3" downpipe and then split it into two 2.5" mandrel bent head and tailpipes to the rear bumper. The mufflers are dynomax long case hemi mufflers with excellent flow and very little restriction.

Is this enough or do I need to do more?

 

I would try it the way you have it and if you think it’s needs to be quieter, just cut out a section of pipe and install one of these.
https://vibrantperformance.com/ultra-quiet-resonators-v1249/
I used one on my truck and it really helped plus got rid of the drone.

 

I used a single 3" resonator and 3" Walker muffler from a local exhaust shop, no high performance stuff just regular muffler for like a van or something. And my 5.3 is quiet as stock 500-600rwhp

Just make sure you look through the resonator that its completely open inside, some of them are not

 

Generally fitting the largest case mufflers you can will do the most. I think the Hemi mufflers are a good step, they have a big case and long travel path. Between that and the turbos you might be as quiet as you need. If they aren't do you have enough room for a second set of large case straight throughs? Another good option is mufflers off of a modern performance car.

 

Just one turbo. Also wastegate will be ran to downpipe

 

If it's too loud how about compound turbos? Lol just kidding. I like stockish exhaust and a cut out for the race track.

 

Compounds do work well to quiet things down

 

Nothing mentioned will give you anywhere near OEM quiet levels of exhaust on a 3.8... not even close.


What you want to do is run a short 3” down pipe with a 3” dump valve. Then run some crush bent 2” piping back to an OEM muffler. This actually gives you OEM sound levels with the dump closed. And flows better than any expensive 3” system would with the dump open. Not to mention its cheaper and lighter than a performance exhaust system.

I did this on my twin turbo mustang 2 3” dumps. Then I Y’d the down pipes to a single crushbens 2.25 all the way to the axle. Then ran a stock axle back 4 cyl mustang walker exhaust system.

 

On my turbo 4.3 s10 I ran full 3 inch with a downpipe I made from a cut up mandrel bent 3 inch full size Chevy truck tailpipe. Biggest reason I did this was cost. The whole tailpipe was less than 40 bucks as mandrel bends were 20 or more each. The tailpipe gave me 6 bends. Then I went in to a stainless Xcelerator brand muffler, which is a straight through design and another full size 3 inch mandrel bent tailpipe. The truck is quieter than my daily driven four cylinder Sonoma! I love it.
Joel