I'm posting here as it seems the best fit of the category offerings.

I have a local performance shop that will make a custom dual exhaust for $800.
That is a full cat back system. I already have a semi-custom exhaust with high flow Y-pipe, high flow resonator, and magnaflow mufflers. With my current exhaust, there is minimal sound increase at idle, slight drone at 2500rpm, roughly 15hp increase. The biggest issue is one that I can't explain: while almost no exhaust noise in the front seat, it is loud and droney in the back seat.

I am looking at this as a sound experiment, and maybe a couple more hp in the higher end. This is for a 3.5L Nissan V6.

The stock piping was 2" off the cats, collected to a crushed to **** 3", then 2.25 back to where it splits for the muffler.

I am trying to decide on the following:

1. Exhaust tubing size - do I keep the factory 2", upgrade to 2.25", or go to 2.5" like the aftermarket Infinity G kits. Maybe start with 2.25 then go to 2.5"

2. H-pipe or X-pipe? Any mustang or truck people want to weigh on on this?

3. Single X muffler in the middle, then straight out the back?

4. Aluminized or stainless? Would be $200 more for stainless

5. Limit drone while keeping a good sound? Tubing size, resonators, mufflers, etc.

Any other considerations?

If I like it, I'll sell the exhaust I currently have. If I don't like it, I'll sell it to someone else.

Thanks.

 

1. Exhaust tubing size - do I keep the factory 2", upgrade to 2.25", or go to 2.5" like the aftermarket Infinity G kits. Maybe start with 2.25 then go to 2.5"

I'm went with a 2.5" exhaust system since I thought it'd be quiet(er) than a 3" but not really. It's a 2002 Nissan Maxima and it's drones around the 2k rpm range. Why not just go to a 3"?

2. H-pipe or X-pipe? Any mustang or truck people want to weigh on on this?

No clue

3. Single X muffler in the middle, then straight out the back?

No clue

4. Aluminized or stainless? Would be $200 more for stainless

Stainless steel + Mandrel bent piping!!

5. Limit drone while keeping a good sound? Tubing size, resonators, mufflers, etc.

Maybe this will help?
https://maxima.org/forums/5th-genera...magnaflow.html

 

More information.

Stock y-pipe:


Current y-pipe: those are 2" that merge to 2.5"


Tunnel before I replaced the resonator and pipe:


And the rear:


Trying to make something that more resembles this, but with a crossover pipe:


The idea I'm kicking around goes as follows:
Off the cats, then to go a few feet, resonators, x pipe, over the axle and then to the mufflers.
Another option is to skip the x pipe, and use an X-through muffler in its place.
Also thinking of staying 2.25 front to back, or possibly 2.5"
Dual 2.25 is a 58% area increase, while 2.5" is a 100% increase.