[TMS]

I thought I would share some sound meter readings for inquiring minds. My car has gone through several iterations of exhaust combinations. Early on I replaced my stock NPP exhaust with a Borla 3" cat back exhaust. I deleted the secondary cats but kept the primary cats. Stock exhaust manifolds and stock primary cats. This represents Scenario 1.

Then after some additional power mods, I needed better flow. I kept the exhaust manifolds stock but ported and opened up the collector outlet. I also deleted the primary cats. I was afraid this would be too loud and so I went ahead and welded in some 3" Vibrant resonators just before the Borla X-pipe. This represents Scenario 2.

After getting the car up and running under Scenario 2, I really liked the exhaust sound but it was just too loud and would cause too much attention. Not good. So I removed the Borla NPP mufflers (axle back) and replaced it with the factory NPP suitcase muffler. This is Scenario 3.

All sound measurements taken at 19.5" away from outer-most exhaust tip at same height and 45 degree angle off to the side.


Scenario 1 (Borla S-Type CatBack w/stock manifolds & secondary cat delete)

Cold start - 115 db
Warm start - 102 db

IDLE
Ice - 77
Tour - 77
Sport - 79
Track - 79

2500 RPM
Ice - 93
Tour - 93
Sport - 93
Track - 93

3250 RPM
Ice - 98
Tour - 98
Sport - 98
Track - 98

4000 RPM
Did not take measurement at this RPM range


Scenario 2 (Borla S-Type with Vibrant resonators, ported stock exhaust manifold & no cats)

Cold start - 111 db
Warm start - 111 db

IDLE
Ice - 89
Tour - 89
Sport - 91
Track - 91

2500 RPM
Ice - 103
Tour - 103
Sport - 103
Track - 103

3250 RPM
Ice - 108
Tour - 108
Sport - 108
Track - 108

4000 RPM
Ice - 116
Tour - 116
Sport - 116
Track - 116


Scenario 3 (Factory Suitcase muffler, Vibrant resonators, ported stock exhaust manifold and no cats)

Cold start - did not take
Warm start - 84 db

IDLE
Ice - 83
Tour - 83
Sport - 85
Track - 85


2500 RPM
Ice - 98
Tour - 98
Sport - 98
Track - 98


3250 RPM
Ice - 101
Tour - 101
Sport - 103
Track - 103


4000 RPM
Ice - 108
Tour - 108
Sport - 109
Track - 109

[Revalot]

Thanks ! I have the borla Atak cat back scenario #1, So that means mine is even louder ! I try to keep a low profile in mine, I have seen people jump when the rev match kicks in ! I stay below 2 grand, but I let her rip in the back woods ! It's good to be in Texas ! LOL !

[Badmojo]

Thanks for posting the data like this! I'm a Mechanical Engineer and this is great.

[TMS]

[Sakudog]

Any video? would be greatly appreciated.

[DFW_Muscle]

Thanks for sharing, a couple of questions:

- Were the readings in scenario 3 with the NPP valves open?
- Did you notice a significantly different tone between Scenario 1 and Scenario 3, or, just volume?
- How long of resonator did you use?

[TMS]

Originally Posted by Sakudog

Any video? would be greatly appreciated.

I have some videos hosted. I’ll post them here.

I was wrong. No sound clip videos of latest setup. All I have is the factory stock video clips and then the Scenario 1 video clips. It likely won't help you but here is the thread link: https://www.camaro6.com/forums/showthread.php?t=530016

I do have a walk-under video clip (no sound) that shows Scenario 3 setup. Here it is: https://youtu.be/60YLmqvGWDk

[TMS]

Originally Posted by DFW_Muscle

Thanks for sharing, a couple of questions:

- Were the readings in scenario 3 with the NPP valves open?
- Did you notice a significantly different tone between Scenario 1 and Scenario 3, or, just volume?
- How long of resonator did you use?

All Scenarios were taken in the each of the 4 various modes. NPP valves operate differently in each of those modes.

Tone between 1 and 3 is different. Scenario 3 is more like stock but louder and it gives some Rice Krispies effect on the decel. Although scenario 3 sure brings out the stink. As well as Scenario 2. Scenario 1 runs louder on highway at light throttle than scenario 3. 3 is much more stealthy like stock until you open the throttle up a bit and then it gets its noise on.

I used the 12 inch. Would have gone for the 18” if I had a do over although it would be a tight fit leading into the X-pipe.

[TheRealJA105]

Can you throw the Borla back on so we can see the difference just between suitcase and Borla without any cats in the mix?

[17CamaroZL1]

Originally Posted by TheRealJA105

Can you throw the Borla back on so we can see the difference just between suitcase and Borla without any cats in the mix?

He did that. It's the difference between scenarios 2 & 3. He only had cats in scenario 1.

[TheRealJA105]

Originally Posted by 17CamaroZL1

He did that. It's the difference between scenarios 2 & 3. He only had cats in scenario 1.

Read too fast, i thought he still had primaries then, thanks.

[17CamaroZL1]

Originally Posted by TheRealJA105

Read too fast, i thought he still had primaries then, thanks.

Happens to the best of us. Lol!!

TMS, did you happen to take measurements of the stock collector? I've heard it's only 2". Can you confirm?

[TMS]

Originally Posted by 17CamaroZL1

Happens to the best of us. Lol!!

TMS, did you happen to take measurements of the stock collector? I've heard it's only 2". Can you confirm?

Yes, I recall it is right at 2". Also, there is enough cast material to port it out at least and additional 3/8" which is what I took it too.

Also updated post #7 with videos.

[17CamaroZL1]

Originally Posted by TMS

Yes, I recall it is right at 2". Also, there is enough cast material to port it out at least and additional 3/8" which is what I took it too.

Also updated post #7 with videos.

Thank you! Really good thread. Love all the details and measurements.