NPP exhaust

[Coz3z3]

Tried searching a little on here, came up with nothing. But was under the car the other day and noticed that the NPP has an H-pipe under there. Was wondering how much improvement it would gain by cutting that out and putting an X-pipe under there.
Improvement as far as sound and gains


Thanks

[Andoskyy]

I have no idea on performance, but i'm sure it would be minimal at best.

After I installed my high flow cats, I had a horrible noise from the NPP. I did EVERYTHING possible to diagnose the noise. There was no rattle, hangers were fine, NPP butterfly valves werent rattling, and I even cut open the mufflers to see if any baffles had broken...they were all fine.

It was loud enough to be embarrassing to drive, so I picked up a 3" Magnaflow catback. It's not as loud, but the noise is gone. The Magnaflow has the X pipe. After more research, I found a lot of info on "H pipe rasp" which sounds like a rattle. I have the NPP in my barn, and I might weld in an X pipe just to see what happens.

[KGoddard]

There are multiple threads on this, like andoskyy said it would be very minimal if any gain, it'll just change the exhaust note

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[Coz3z3]

Ok Interesting, I figured it would be very minimal but wanted to double check. That is good to know about going wth high flow cats and that rattle though.

Thanks guys

[KGoddard]

Originally Posted by Coz3z3

Ok Interesting, I figured it would be very minimal but wanted to double check. That is good to know about going wth high flow cats and that rattle though.

Thanks guys

I have long lube headers with no cats and I have the NPP system and i have not experienced any odd noises. I would not be worried about that for your future exhaust plans...

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[SlingShot]

Originally Posted by Coz3z3

Ok Interesting, I figured it would be very minimal but wanted to double check. That is good to know about going wth high flow cats and that rattle though.

Thanks guys

Running Solo HF cats here, and never had a problem. Is it loud, yes but not header loud and only gets loud when you put your foot in it.

[Aug]

Originally Posted by Coz3z3

Tried searching a little on here, came up with nothing. But was under the car the other day and noticed that the NPP has an H-pipe under there. Was wondering how much improvement it would gain by cutting that out and putting an X-pipe under there.
Improvement as far as sound and gains


Thanks

I have done EXACTLY this. I have 2014 SS with factory NPP exhaust. I found it a little louder than I would prefer, and a little raspier I guess - harsh. I want a deeper/softer tone - more bass less trebble LOL. Keeping the NPP system always in quiet mode using my Forza controller was not to my liking either. So for $100 I had a shop take out the H pipe and install an X pipe. Interestingly, unless you are very intimately familiar with the sound of your car, the difference is hard to notice. I will say it is slightly quieter, slightly less harsh, slightly less rasp. No reduction in decelleration popping. All in all, this is probably ok for me, better than factory, but I expected and wanted a deeper lower tone. I am afraid a resonated X pipe would be too quiet, so I will leave this as-is now. It is better, and for $100 its cheap. BTW, no performance difference, but didn't expect a performance difference anyhow.

[Rubbershredder]

https://m.youtube.com/watch?v=fCio5K0WfHU