[WhyUMad1LE]

I like the stock NPP sound with valves closed but not with valves open (want a deeper tone).

I'd like to make my own NPP system utilizing the OEM valves and running Flowmaster Super 10s to the outer tips. Looking at the OEM suitcase muffler, when the valves are closed it uses a crossflow system to make things quiet. I'm looking to stick a transverse muffler in that space that will operate when valves are closed.





How I would route the center muffler:




The options I've seen so far are
Borla ProXS https://www.borla.com/Borla_ProXS_Mu...Wall_Chart.pdf
Flowmaster 80 https://www.flowmastermufflers.com/p...ressive-sound/
Thrush Turbo http://www.thrushexhaust.com/muffler...al-offset.html
Walker Quiet Flow https://www.summitracing.com/parts/wlk-22395/overview/

Anyone know of others?

[cmitchell17]

I completely agree with you, the NPP in stealth mode sounds pretty good, besides the rattle, but that's another issue. What do you mean by crossflow? The two exhaust sides go into one chamber?

When the NPP opens at WOT it sounds like a obnoxious straight piped truck with way too much rasp, and is way to loud in my opinion to keep away the attention of do gooders.

[WhyUMad1LE]

Originally Posted by cmitchell17

I completely agree with you, the NPP in stealth mode sounds pretty good, besides the rattle, but that's another issue. What do you mean by crossflow? The two exhaust sides go into one chamber?

When the NPP opens at WOT it sounds like a obnoxious straight piped truck with way too much rasp, and is way to loud in my opinion to keep away the attention of do gooders.

Yes, I like a more bassy rumble than a high pitched rasp.

A crossflow muffler is mounted transversely. The direction of exhaust flow is as below.

[G2K]

Below is the hookers exhaust, which is what i have currently on my car... The deep tone was there until i removed my high flow cats from my kooks headers.... no matter what you do no cats = rasp on these cars, i hate it but yes. I think it has to do because these cars are X-pipped i/o H-pipe.

[Mark114]

Hooker has some similar options:

[WhyUMad1LE]

^^The Hooker isn't deep enough to me. I want to do a custom setup, Flowmaster 10s or Thrush Rattler with valves open & the transverse muffler valves closed.

[Chef-j]

What inlet/outlet size are you going for?

[z28pat]

That’s a good idea , is it possible to get the valves closer to the y where the pipes split?

[WhyUMad1LE]

Originally Posted by Chef-j

What inlet/outlet size are you going for?

Whatever fits closest to stock piping. Although if it comes down to it, a half inch difference here and there isn't a big deal.

Originally Posted by z28pat

That’s a good idea , is it possible to get the valves closer to the y where the pipes split?

The valve actuators are mounted by the exhaust tips, so you would have to relocate them and deal with the wiring as well. Too much of a PITA for me.

You can see here someone routed new mufflers to the stock tips w/ NPP valves.