[Rodan]

It's still a work in progress, and I haven't had much time to make progress...

I did section the bends today (to open the angle a bit) and tacked them back together.




Still have quite a bit to do to finish them. 3" fits perfectly into the stock tips.

We're three weeks out from a 95dB trackday, so I need to get them finished. I'll post a thread when I finish them and link to it from here.

[dlct3]

Originally Posted by Rodan

It's still a work in progress, and I haven't had much time to make progress...

I did section the bends today (to open the angle a bit) and tacked them back together.


Still have quite a bit to do to finish them. 3" fits perfectly into the stock tips.

We're three weeks out from a 95dB trackday, so I need to get them finished. I'll post a thread when I finish them and link to it from here.

Are you otherwise a stock car? Thanks

[Rodan]

Yes, ours is stock/ stock exhaust. Having talked to other local ZL1 owners at the track, I know even stock exhaust won't pass 95dB.

Some local C7 ZO6 (which also blow sound stock) guys have passed doing similar mods, so I'm hoping these bends will attenuate it just enough to pass.

[sv340]

I am curious to see how you secure the pipe into the exhaust.

[GunMetalGrey]

What about adding these down turn race mufflers from FlowMaster to just the valved pipe exiting the muffler only, so that the pipe with all the noise coming out of it is reduced. Do this by cutting the tips and making connection flanges with bolts so the tips can be switched and this 6” muffler can be attached and stick out of the rear valence where the 2 tips were.

https://www.flowmastermufflers.com/p...derate-sound/?

Thoughts?

[dlct3]

Originally Posted by GunMetalGrey

What about adding these down turn race mufflers from FlowMaster to just the valved pipe exiting the muffler only, so that the pipe with all the noise coming out of it is reduced. Do this by cutting the tips and making connection flanges with bolts so the tips can be switched and this 6” muffler can be attached and stick out of the rear valence where the 2 tips were.

https://www.flowmastermufflers.com/p...derate-sound/?

Thoughts?

The same idea has crossed my mind. I envisioned a Vibrant v band clamp system to either a laguna pipe with a muffler insert or something like this you sent. That way I can easily convert back to the factory tip with the quick release vband clamp system. The weight of a muffler is my only concern during track time. Wondering if it would split at the suitcase joint if not utilizing some sort of bracing.

I bought a DB meter. So I’ll gather some readings at 50’ under load. Post those and start testing I suppose with maybe some 3” 90 degree pipes.

Does anyone know of an axle back system quieter than the stock NPP?

[GunMetalGrey]

Originally Posted by dlct3

The same idea has crossed my mind. I envisioned a Vibrant v band clamp system to either a laguna pipe with a muffler insert or something like this you sent. That way I can easily convert back to the factory tip with the quick release vband clamp system. The weight of a muffler is my only concern during track time. Wondering if it would split at the suitcase joint if not utilizing some sort of bracing.

I bought a DB meter. So I’ll gather some readings at 50’ under load. Post those and start testing I suppose with maybe some 3” 90 degree pipes.

Dours anyone know of an axle back system quieter than the stock NPP?

Apparently Borla Stype was made specifically to stay under 95Dba

[dlct3]

Originally Posted by GunMetalGrey

Apparently Borla Stype was made specifically to stay under 95Dba

OK, Thanks I'll see if I can locate one.

You got me re-thinking the additional muffler... so I started searching and here is what I've narrowed it down to through Summit Racing. I'd prefer nothing more than a 12" body for weight purposes. Took some measurements and found that a 4" case is as big as I could make work and be able to attach it very close to the 2 muffler hangers on that outside NPP exhaust. I don't believe a support would be needed if utilized. Check these links out and let me know what you think? I'd attach a 90 degree mandrel with approx. 6" leg on the other end with the V-band joint closest to muffler.

https://www.summitracing.com/parts/mor-94054

https://www.summitracing.com/parts/mpe-10416

https://www.summitracing.com/parts/wlk-24246

https://www.summitracing.com/parts/mor-94050

[Rodan]

Couple of things to remember:

Any kind of actual muffler will get pretty hot, much hotter than a piece of straight pipe in the same location... the absorbed sound energy will be converted to heat. Therefore, it needs to be away from any part of the plastic bumper.

Any kind of steel/stainless muffler will be heavy. Having that weight hanging out on a lever arm will require pretty significant support. Something like an aluminum motorcycle muffler may be a better option to reduce weight. This is why I'm starting with a simple bend to redirect the outlet. If that doesn't work, I'll look into plan B...

If I do have to do 'plan B', I think the V band idea is a great way to go. I had actually planned to do that with the pipe bends, until I realized it really wasn't necessary since a 3" pipe slides into the stock tips.

Finally, you want the exit to be pointing up and/or away from the measuring devices. If it points at the ground, the sound reflections and reverberation off the track surface may defeat any reduction in dB.

[dlct3]

Originally Posted by Rodan

Couple of things to remember:

Any kind of actual muffler will get pretty hot, much hotter than a piece of straight pipe in the same location... the absorbed sound energy will be converted to heat. Therefore, it needs to be away from any part of the plastic bumper.

Yes, Good point. I figured I'd wrap it all in header wrap as well.

Any kind of steel/stainless muffler will be heavy. Having that weight hanging out on a lever arm will require pretty significant support. Something like an aluminum motorcycle muffler may be a better option to reduce weight. This is why I'm starting with a simple bend to redirect the outlet. If that doesn't work, I'll look into plan B...

Ya, this is my dilemma.. Just a Laguna pipe won't cut it for my car. I can't decide on whether to buy a 12" like in the links above or the Magnaflow 14" which I think will be quietest. My next dilemma is whether to cut the tail off down to nothing or a 1/2" and weld it directly to the vband which will stick out 7-9" past current tip before the exiting 90 degree mandrel is welded on to the exit side for proper air diversion. Or, add vband to 2 1/2" pipe exiting about 8" +/- from vband joint then have a 65-90degree mandrel bend with 12-14" muffler going up and away to one side. I'm just not sure which suspended weight is best.

If I do have to do 'plan B', I think the V band idea is a great way to go. I had actually planned to do that with the pipe bends, until I realized it really wasn't necessary since a 3" pipe slides into the stock tips.

Finally, you want the exit to be pointing up and/or away from the measuring devices. If it points at the ground, the sound reflections and reverberation off the track surface may defeat any reduction in dB.

Thanks for the input! Feel free to chime in. I hate to spend all this time/money for nothing, but need it to be effective and be easily changeable. The Vband clamp idea was Jordan Best over at Garage Therapy which seems genius.

[GunMetalGrey]

Originally Posted by dlct3

OK, Thanks I'll see if I can locate one.

You got me re-thinking the additional muffler... so I started searching and here is what I've narrowed it down to through Summit Racing. Check these links out and let me know what you think? I'd attach a 90 degree mandrel with approx. 6" leg on the other end with the V-band joint closest to muffler.

https://www.summitracing.com/parts/mor-94054

https://www.summitracing.com/parts/mpe-10416

https://www.summitracing.com/parts/wlk-24246

https://www.summitracing.com/parts/mor-94050

Check out the comments in the review sections of these products; I would t buy any of them. Then check out the FlowMaster comments in the links I provided below.

1 review says the Moroso is only slightly less aggressive than the Flowmaster 10 series which is very loud, I think Flowmaster’s loudest actually! But then another guy says it quieter his car down more than expected when added onto the exhaust system he already had.

Another review said the dynomax sounds like a NASCAR at WOT and that the MagnaFlow option was quieter than this ooption.

Apparently the Borla XR1 is very loud as well but not as loud as the MagnaFlow option you listed.

The customer reviews on the FlowMaster are the only ones that say they have good sound control and quiet the car down enough to meet tough track sound restrictions
https://www.summitracing.com/int/par...3-664ec95149bf

https://www.summitracing.com/int/par...12100/reviews/

But then some other reviews say they are loud...

https://www.summitracing.com/int/parts/flo-13016100/

I know “loud” is subjective, but still frustrating to see all the different opinions...
Only Moroso and Flowmaster seem to describe sound control in the product description and with Flowmaster it was rated at moderate to mild sound level compared to the their own 10 and 40 series.

[Rodan]

Exhaust is kind of like suspension... it's too subjective to make any kind of reasonable comparison. Even listening to different YT vids is pretty useless, unless exhausts are compared side/side on the same video, shot with the same equipment.

[GunMetalGrey]

I talked to summit racing, they believe that any of the straight through designs will tend to be the loudest and hence felt that the laminar flow of the Flowmaster would also be the quietest... they also have the largest diameter out of the options listed (6” vs 4”) and I would think they’d be using that space to get more sound control.

[BDivine76]

I may have missed this...sorry if I did, but at what distance are they measuring SPL? Sound follows the inverse square law (double the distance and get a 6dB drop in SPL). This is true from 1ft to 2ft, 2ft to 4ft, etc. Distance will have a huge impact so I am just wondering what the reference point is.

I've been looking into this because of the new fine structure in CA, but here the distance is 19.5 inches from the exhaust...extremely tough. I did a quick down and dirty (Borla ATAK axle back) and saw 89dB at idle and 94.5 @ 2500 rpm. This was not with a calibrated mic however...so it could be off.

Just wondering what they are doing at tracks as I plan to do a few events this spring/summer.