[utekineir]

Before the pitchforks come out, this is soely about passing noise limits at autocross/track events. Being a shitty neighbor pisses off the nimbys and loses venues.

In particular staying <89 db @ 75 feet in a range of assorted ambient conditions, cloud cover, humidity, wind etc all give enough variance that sitting near the limit can equal going over easily in less than ideal conditions.

Buying the car at the end of last season my quick solution to get by was having drilled vertical holes just inside of the valves and dropping pins through at events, there did feel to be a loss in response. The valves open maybe 25% with where i located the pin holes.

What i'm looking for is off the shelf resonated axleback options that are quieter than fully open npp (it goes open at wot regardless of mode setting, pulling the fuse is not workable either). Xpipe or cat removal would negate the goals, so likely an axleback makes the most sense. Giving up the npp is fine, I've used dummy plugs in the past on other applications when removing valved exhaust.

If i'm not wrong with the npp open the outer pipes are basically a passthrough. So feasably having resonators for all tips should be effective if the resonators are halfway decent.

goals: Stop crawling under vehicle every weekend, get back some of the lost response,

minor goal: possible better quality sound?

thanks,

[cjperformance]

Something to consider, and look into, since im not positive you can do this.... but you may be able to lock the npp valves closed (quiet mode) via a tune change. I believe there are some tweaks in the tune to open or close the valves in whatever manner you want.

If i recall there were tweaks for throttle percentage, rpm, etc... if so, it would satisfy at least one goal of not having to get UNDER the car.

[Big Mikey]

Originally Posted by cjperformance

Something to consider, and look into, since im not positive you can do this.... but you may be able to lock the npp valves closed (quiet mode) via a tune change. I believe there are some tweaks in the tune to open or close the valves in whatever manner you want.

If i recall there were tweaks for throttle percentage, rpm, etc... if so, it would satisfy at least one goal of not having to get UNDER the car.

I thought I saw someone's old post on here (maybe a year or so ago) where they kept the valves closed during an auto-x or track day and melted their rear fascia. I believe they kept the valves in stealth mode. I'll try and search for it and edit this post if I find it...

To the OP, I know some folks use Laguna Seca pipes, but I don't think that solves your issue as they simply help direct the noise to a certain direction.

However, check out the following thread, the poster in this thread added an additional muffler to reduce sound: https://www.camaro6.com/forums/showthread.php?t=576096

Edit: Found the example of melted fascia with NPP in stealth mode. Post 6 in the following link: https://www.camaro6.com/forums/showthread.php?t=585360

[d15b7]

Hi. Be careful with this; I don’t think it would ever be an issue at a autox (too short a run time to get it overheated) but at track events there have been guys who locked the valves in closed mode and melted the rear bumpers and damaged their cars

[WhiteMale]

Yep we've seen that old thread about valves closed, Chevy says in the manual or the supplement to not do that. Guy melted his rear bumper cover.

[Vigilante375]

As mentioned, DO NOT KEEP THE VALVES CLOSED. It will damage the exhaust and the car. And it is mentioned in the manual to never keep the exhaust valves closed while racing. Do the "laguna" pipe setup and you'll be fine.

These noise restrictions are stupid but I understand why it's there. But a rule should be added that if the vehicle is as it was from the factory, then the noise requirement shouldn't apply to it.

[utekineir]

Originally Posted by Vigilante375

These noise restrictions are stupid but I understand why it's there. But a rule should be added that if the vehicle is as it was from the factory, then the noise requirement shouldn't apply to it.

The issue with that is that the sound carrying isn't announcing to any of the complaining parties wether its a factory or aftermarket exhaust. Gt3 locally generally have to block off the valves as well. The complainers cant do anything about the packs of harleys cruising around putting out as much sound or more the constant planes overhead or the adjacent gun range. But they can cause an issue for us and have made it an issue for years.





Had read through all the melted bumper threads last fall, thanks everyone.

Re the not getting under car bit, i'd happily give up the npp for a consistent level that didnt require ****ery every weekend, It takes no real time to set stealth mode, drop the pins in and then set back to track but blocking the valves feels like a kludge, and for the above mentioned concerns of damage seems not ideal long term, also it would be nice to get the pedal response back. The car has plenty of power either way, but blocked does feel blunted.

Locally an lt4 does not pass sound when driven hard in stock form c7 or camaro6, In past years I've tried to help people with lt4 engines pass sound via modes, fuse pulling and basically whatever was on hand, so i knew what i was getting into off the bat and showed up with a solution that kept it legal and running.

I had hoped something like an awe touring could be the ticket but i'm doubtful based on youtube videos the crowd looking to drop sound levels basically doesnt exist. So its hard to find a good comparison video that doesnt include cat removal, headers, etc.

[CW3SF]

Originally Posted by utekineir

The issue with that is that the sound carrying isn't announcing to any of the complaining parties wether its a factory or aftermarket exhaust. Gt3 locally generally have to block off the valves as well. The complainers cant do anything about the packs of harleys cruising around putting out as much sound or more the constant planes overhead or the adjacent gun range. But they can cause an issue for us and have made it an issue for years.





Had read through all the melted bumper threads last fall, thanks everyone.

Re the not getting under car bit, i'd happily give up the npp for a consistent level that didnt require ****ery every weekend, It takes no real time to set stealth mode, drop the pins in and then set back to track but blocking the valves feels like a kludge, and for the above mentioned concerns of damage seems not ideal long term, also it would be nice to get the pedal response back. The car has plenty of power either way, but blocked does feel blunted.

Locally an lt4 does not pass sound when driven hard in stock form c7 or camaro6, In past years I've tried to help people with lt4 engines pass sound via modes, fuse pulling and basically whatever was on hand, so i knew what i was getting into off the bat and showed up with a solution that kept it legal and running.

I had hoped something like an awe touring could be the ticket but i'm doubtful based on youtube videos the crowd looking to drop sound levels basically doesnt exist. So its hard to find a good comparison video that doesnt include cat removal, headers, etc.

AWE Touring sounds amazing but it is way way louder than the stock suitcase. Resonators are really the only way to bring exhaust noise levels down.

[ST1LE]

Magnaflow makes a resonator that will do what you are looking for. Much cheaper than a axleback exhaust too.

Edit: This is what I was referring to. Cheapest option out there($150 + install), worth a try I think.

https://www.phastekperformance.com/C...hoCcqoQAvD_BwE

[Gunkk]

Originally Posted by utekineir

If i'm not wrong with the npp open the outer pipes are basically a passthrough. So feasably having resonators for all tips should be effective if the resonators are halfway decent.

Yes it's a passthrough. Tip resonators might work if you can fit them and not cook the diffuser. Are laguna pipes are an option?

[utekineir]

Originally Posted by ST1LE

Magnaflow makes a resonator that will do what you are looking for. Much cheaper than a axleback exhaust too.

Edit: This is what I was referring to. Cheapest option out there($150 + install), worth a try I think.

https://www.phastekperformance.com/C...hoCcqoQAvD_BwE

Thanks. Will look into that.

Originally Posted by Gunkk

Yes it's a passthrough. Tip resonators might work if you can fit them and not cook the diffuser. Are laguna pipes are an option?

Turndowns are ok, Laguna pipes are not and are a dick move in this case. Also, since I regularly work sound assignments, talking to people when they go over and explaining the rules are about keeping the site for everyone and then cheating it myself is a bad look.

I've seen the burns an unwrapped turn down can cause when a person in shorts walks around the back of a vehicle close and bumps one. Not anything I want to be a part of.