Muffler suggestions for tracks with sound restrictions??

[Kobie]

Not to be confused with the typical "which muffler sounds/performs best" threads. There is a local track that strictly enforces a 94dB limit for cars/bikes on track. By strict I mean you have to do a test session driving by multiple SPL meters, including one monitored by the city, to receive a sticker certifying compliance. I'm running a supercharger, full length headers, hi flow cats, H pipe and Corsa mufflers and there is no way in hell I'm going to pass. I'd rather not put the stock mufflers back on, but it might be the only option. Is there anyone here running at sound restricted tracks, or even at AMP here in Phoenix and if so what are you running? Thanks!

 

[jmauld]

94db is pretty loud. Can you stop by that track and have them measure it for you?

 

[Norm Peterson]

A number of autocross sites have a 96db limit in place. I also think it's "A-weighted, slow response", which means something to the noise guys.

Anyway, if you can find out what any of the C Prepared autocrossers are doing to quiet those beasts down that might give you something to start with.


Norm

 

[erat]

Similar set up. No way you are passing. I am going to try resonators to tone it down a bit.

 

[DusterRT]

2010 GT500 mufflers, or Cor$a Touring. Although with your setup, stock mufflers might be the best way to beat down the sound (and it won't sound bad either to be honest!).

 

[Chris B.]

I'd say stick with the stock mufflers.

 

[Kobie]

94db is pretty loud. Can you stop by that track and have them measure it for you?

Yeah, they have testing session days. I just know that my setup won't pass so I'd rather have a "safe" solution before trying.

A number of autocross sites have a 96db limit in place. I also think it's "A-weighted, slow response", which means something to the noise guys.



Anyway, if you can find out what any of the C Prepared autocrossers are doing to quiet those beasts down that might give you something to start with.


Norm

A weighting is a measurement for industrial environments at a limited bandwidth of frequencies. Slow is how fast the "needle" swings. C weighting is for A/V environments where you need to measure a full frequency response. Can you guess what I do for a living?

Similar set up. No way you are passing. I am going to try resonators to tone it down a bit.

I thought about using a Pro Chamber, but I don't think that will help the overall SPL. Maybe it might make it sound better, but at $300 it's an investment.

2010 GT500 mufflers, or Cor$a Touring. Although with your setup, stock mufflers might be the best way to beat down the sound (and it won't sound bad either to be honest!).

Will the 2010 GT500's fit on an '07 GT? I thought they would be different on the newer body styles.

I'd say stick with the stock mufflers.

This is kind of where I thought I'd end up at. Those end pipes look pretty wimpy though.

 

[DusterRT]

Will the 2010 GT500's fit on an '07 GT? I thought they would be different on the newer body styles.

Yep, they'll go right on, had them on my '08 and loved them (notably louder than the Corsa Touring I had on before though, I ran them with a high flow cat'd X-pipe). They changed the hangers in '11, so the '10 GT500's are a one year only thing.

Now that I think about it, Collin ran long tubes, off-road X or H and stock GT mufflers on his Griggs car, which they used at Infineon and Laguna. Must have been quiet enough, and I thought it sounded pretty good.

 

[Norm Peterson]

A weighting is a measurement for industrial environments at a limited bandwidth of frequencies. Slow is how fast the "needle" swings. C weighting is for A/V environments where you need to measure a full frequency response. Can you guess what I do for a living?

I guess that makes my next question "are they measuring the sound in a manner appropriate to the activity, or are you getting penalized somehow?" The little that I know about this stuff includes the understanding that extraneous sound either on or off site can/will adversely affect your reading.

Will the 2010 GT500's fit on an '07 GT? I thought they would be different on the newer body styles.

If the mufflers will physically fit into the space provided, there's nearly always a way to get them connected and hung.


Norm

 

[VTXFrank]

Why not just go to the track next time people are racing and ask those who race there? They will be able to best inform you before you go out and spend any $$.

 

[Sam Strano]

Hey Kobie.... One of those things I have a lot of (and decent pricing on for the most part) are exhausts. I also know a little about them too.

Are you running an axle-back or a cat-back now? I ask because not all mufflers will work with all cat-backs. But I've got some ideas/options. You know where to find me.

 

[Kobie]

I guess that makes my next question "are they measuring the sound in a manner appropriate to the activity, or are you getting penalized somehow?" The little that I know about this stuff includes the understanding that extraneous sound either on or off site can/will adversely affect your reading.

Norm

I think it is. Cars don't put out a lot of bass unless you are crankin' the stereo! Since the track is at the end of an Air Force base they can tell the difference between cars and planes, so they take that into account. Apparently the locals don't have a problem with F16's flying over, but cars!! Oh my!!

Why not just go to the track next time people are racing and ask those who race there? They will be able to best inform you before you go out and spend any $$.

Great advice! They don't have anything on the calendar in the foreseeable future so I might have to take a WAG.

Hey Kobie.... One of those things I have a lot of (and decent pricing on for the most part) are exhausts. I also know a little about them too.

Are you running an axle-back or a cat-back now? I ask because not all mufflers will work with all cat-backs. But I've got some ideas/options. You know where to find me.

I have axle backs. I'd love to hear what you have to say about this. You haven't given me bad advice yet! Maybe I'll give a call after the holiday.

 

[Kobie]

I took SPL readings on the car this morning at start up just for the heck of it. 96dB during warmup and 91dB at idle after warmup. That was at about 20ft behind the car. LOUD!!

 

[erat]

Yep, told you. Sounds like a tractor too when it's cold. Try adding cams, it makes it worse.

 

[Kobie]

Crane NSR2's. Forgot to mention.

 

[Mach2burnout]

A set of resonators will help a lot without affecting power or a least a very minimum affect on power. Would probably get you where you want to be and get rid of the trumpeting.

I don't get where your stock mufflers will be that much quieter with the mods you have. When I had mine w/ OR x and H pipes it was loud as hell, especially under acceleration and deceleration. And I didn't even have headers or cams.

 

[Kobie]

What resonators might you suggest? The only thing I've seen is the Mac Pro Chamber and I'm not sure if that even qualifies as a resonator.

 

[Mach2burnout]

There's very little difference between a resonator and a glass pack muffler. Do a search, there are several threads on this subject. IMO you want one that is louvered rather than perforated. I think they sound a little better. I just installed a cheap 1' long louvered glass pack muffler, with my flowmaster axle backs. Now again keep in mind I don't have cams or LTs so really my info may not help you but mine is not nearly as unbearable as it was before with just the FMs.

 

[Mach2burnout]

Check out this thread, it has some good info on resonators

http://www.s197forum.com/forum/showthread.php?t=68569&highlight=resonators

 

[ArizonaGT]

AMP?

Stock mufflers or bullet mufflers with turndown tips. I think any sort of "chambered" muffler would work.