[KingLT1]

A Long tube header car with no cats and any NPP system will be stupid loud @ wot. The reason being the exhaust valves open and it's basically a straight pipe system at that point no matter if it's stock, Borla, SW, Flowmaster....

There are a couple potential options.


1) If you have Hp tuners, You can try programming the Npp valves to stay closed at all times in 1 of the performance modes, so the exhaust is routed through the mufflers at all times.

2) Another option that might work is to switch to a non NPP exhaust. The MBRP Street system sounds really nice. Not very popular because most opt to go for Loud.

3) Add high flow cats and a set of resonators in the mid pipe section similar to what Borla offers with the 60608. That will probably knock 10-15db off the noise level.

[oldman]

Originally Posted by gmcvt

What?? I thought you were happy with the 2 cat/60608 arrangement. What happened?

Just bored.... I am going to LT cats and Bola 60608 soon (like today), and will post a video of that too.


Now that the 60608 is on I can do:
all 4 cats (front two modified for flow) 60608 the stock after that for max quiet
CA front cat deletes, factory 2nd cats 60608 the stock after that for slightly louder than factory at low throttle going down the street, which as noted is the best so far
LT, high flow cats and then 60608 the stock after that for max performance, bout as loud as a FBO car with say Borla ATX at WOT, don't really know how it will be on the street as my battery died and I just put a new battery in yesterday.

[Baddawg53]

Originally Posted by supersportss

SLP has some slip on mufflers that work awesome, I used it on my 4th gen Firebird when it was way to loud, check them out they should help.

I will check that out ... Easy on and off would be ideal, I want to keep the Atak on other than at the track.

[Baddawg53]

Originally Posted by KingLT1

1) If you have Hp tuners, You can try programming the Npp valves to stay closed at all times in 1 of the performance modes, so the exhaust is routed through the mufflers at all times.

2) Another option that might work is to switch to a non NPP exhaust. The MBRP Street system sounds really nice. Not very popular because most opt to go for Loud.

3) Add high flow cats and a set of resonators in the mid pipe section similar to what Borla offers with the 60608. That will probably knock 10-15db off the noise level.

I definitely want to use a non NPP muffler. I currently have a remote control on the NPP valves so I have total control of them, but I know you're not supposed to run it hard with them closed. I also have the high flow cats installed, and have already ordered the 60608 resonator. Just trying to figure out now what to do with a muffler to get it somewhat close.

[gmcvt]

Originally Posted by oldman

Just bored.... I am going to LT cats and Bola 60608 soon (like today), and will post a video of that too.


Now that the 60608 is on I can do:
all 4 cats (front two modified for flow) 60608 the stock after that for max quiet
CA front cat deletes, factory 2nd cats 60608 the stock after that for slightly louder than factory at low throttle going down the street, which as noted is the best so far
LT, high flow cats and then 60608 the stock after that for max performance, bout as loud as a FBO car with say Borla ATX at WOT, don't really know how it will be on the street as my battery died and I just put a new battery in yesterday.

You have a stock Non-NPP exhaust, correct? (I see the Borla 60609 in your sig but I assume that is suppose to be a 60608)

[TheRealJA105]

Originally Posted by Baddawg53

I definitely want to use a non NPP muffler. I currently have a remote control on the NPP valves so I have total control of them, but I know you're not supposed to run it hard with them closed. I also have the high flow cats installed, and have already ordered the 60608 resonator. Just trying to figure out now what to do with a muffler to get it somewhat close.

You aren't supposed to run it hard with the valves closed on the STOCK EXHAUST. Won't be an issue on your higher flowing Borla ATAK, that's why he recommended it. I would bet the internals of the Non NPP ATAK look just like the NPP ATAK on the muffled side.

[Redlinez]

I seem to remember years back people liked these https://www.summitracing.com/parts/v...RoCwRwQAvD_BwE

[Baddawg53]

Originally Posted by TheRealJA105

You aren't supposed to run it hard with the valves closed on the STOCK EXHAUST. Won't be an issue on your higher flowing Borla ATAK, that's why he recommended it. I would bet the internals of the Non NPP ATAK look just like the NPP ATAK on the muffled side.

I know my Atak has 2- 2 1/4" outlets, so you are going to choke it down a half inch by closing the valve into one outlet. I'm comfortable driving around my neighborhood like that but I'm not sure if a track is a good idea.

[KingLT1]

Originally Posted by TheRealJA105

You aren't supposed to run it hard with the valves closed on the STOCK EXHAUST. Won't be an issue on your higher flowing Borla ATAK, that's why he recommended it. I would bet the internals of the Non NPP ATAK look just like the NPP ATAK on the muffled side.

Exactly.

Originally Posted by Baddawg53

I know my Atak has 2- 2 1/4" outlets, so you are going to choke it down a half inch by closing the valve into one outlet. I'm comfortable driving around my neighborhood like that but I'm not sure if a track is a good idea.

I doubt it's going to hurt anything other then you "might" give up a few hp. Food for thought, the power rating between the SS with non NPP and the NPP exhaust is basically the same. The single tip outlet is larger but being clear at the back of the exhaust system, velocity has slowed to a point where 2 1/4-3" outlets make very little difference. Hence why the crush section has no effect on power.

[Baddawg53]

Originally Posted by KingLT1

Exactly.



I doubt it's going to hurt anything other then you "might" give up a few hp. Food for thought, the power rating between the SS with non NPP and the NPP exhaust is basically the same. The single tip outlet is larger but being clear at the back of the exhaust system, velocity has slowed to a point where 2 1/4-3" outlets make very little difference. Hence why the crush section has no effect on power.

I don't necessarily disagree with you, and I do run around town with then closed, but before I start running WOT at 7000 RPM, I'd kinda like some proof it won't cause any issues. Peace of mind ...

Maybe I'll call Borla and see what they recommend...

[oldman]

Originally Posted by gmcvt

You have a stock Non-NPP exhaust, correct? (I see the Borla 60609 in your sig but I assume that is suppose to be a 60608)

Yeah typo been too lazy to fix, the kid took my computer for school when his died (too many video games) we are talking house fans water cool overclock job. I'm on the oldlady's laptop and the screen is buku small.

[cmitchell17]

Originally Posted by oldman

Just bored.... I am going to LT cats and Bola 60608 soon (like today), and will post a video of that too.


Now that the 60608 is on I can do:
all 4 cats (front two modified for flow) 60608 the stock after that for max quiet
CA front cat deletes, factory 2nd cats 60608 the stock after that for slightly louder than factory at low throttle going down the street, which as noted is the best so far
LT, high flow cats and then 60608 the stock after that for max performance, bout as loud as a FBO car with say Borla ATX at WOT, don't really know how it will be on the street as my battery died and I just put a new battery in yesterday.

What did you do to modify your front cats for flow?

[OneSlowV]

Thank me later you will be amazed what these do .

https://www.amazon.com/gp/aw/d/B08D9...b_b_asin_image

[Cali SS Camaro]

New to the group and researching exhaust systems for my 2016 SS. What is a "custom laguna pipe"?