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JMortensen

Too loud for track noise requirement

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Car was too loud at the autox. Sound limit is 96 dB, I went past the meter at 102. 5.3L with 2.5" sidepipes into 18" long mufflers that I made. I tried to ape the Burns Stainless super quiet one by welding angle into the flow path in 2 spots at 90 degree angles to each other. I think the problem is that my muffler is pretty small in diameter at 4". Would have done 6", but there just isn't room for it.

I put V band clamps on both ends of the muffler, so I could just swap it out entirely for something else, or add another muffler, or change the tip. My thought right now is to repack with ss steel wool (the fiberglass I put in has apparently left the muffler). Seeing bulk stainless wool on ebay, is that the best place to get it, or is there something better to use? Then add supertrapp tips and just take plates out until it makes the dB requirement. I really don't like supertrapps in general, but that seems to be the most cost effective solution from what I've seen so far.

There are other bullet mufflers that I could just weld a vband flange to and bolt to the back of this one and that might even be cheaper than the trapp, but I'm kind of worried that I won't get enough out of that and then I'll need the something like the trapps on the end of that.

Better idea?

 

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Definitely not going to run cats on my carbed, side piped V8. I'd think I'd have a pretty good chance of burning the paint off of the rockers. Right now I'm still mulling adding a second muffler (maybe a spiral flow instead of a straight through) or doing Supertrapps on the end. I don't like Supertrapps, generally speaking, but I know I could just take plates out until I hit the number I wanted, so it has that advantage.

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Lift near the meter, then get back on it, working this out is going to steal a lot of quality time from you.  Or start drag racing-we like loud cars!  SCCA is really getting annoying with this politically correct sound stuff.  Try wearing a smoking jacket, a derby, and an ascot, and talk like you have a pickle up your arse, and maybe they will be nicer and let you race.  Better yet, put an old "Obama/Biden 2008" sticker on your car and they won't try to enforce any of their rules.  Or a "Hillary in 2016" and they will be too scared to hassle you.  Or come drag race in God's country and we will welcome you with open arms-wide front tires and all!

Edited by RebekahsZ

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Not worried about the time. We just turned the lights off up here. It will be dark and rainy until May, summer usually starts July 5th. Not sure if I'll run in the spring, depends on if I can find rain tires. Either way, I've got a few months to sort things out.

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Lift near the meter, then get back on it, working this out is going to steal a lot of quality time from you.  Or start drag racing-we like loud cars!  SCCA is really getting annoying with this politically correct sound stuff.  

 

Really?  102dB is really loud, it's not a huge power hit to drop that below that fairly generous 96dB limit.

Edited by SleeperZ

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I have a friend who owns the company that makes the Brunton Stalkers.  The Brunton M-Spec cars come with LS Engines and have side pipe exhaust.  The sound of his cars is very nice, and well below the SCCA dB limit. He uses  catalytic converters in line with the mufflers to keep the exhaust quiet.  If you give him a call (Scott Minehart), he can tell you which mufflers and cats he uses.

 

http://stalkercars.com/

 

Here is his car on track.

 

 

 

post-30-0-97792600-1445813403_thumb.jpg

Edited by 74_5.0L_Z

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spiral flow will help IMO.

Turndowns may help depending on the meter point.. V-band them and rotate to your liking. I had mine turned at 45 degrees on my GTO and it was louder in-cabin but quieter outside. In disappointment, I cut them off and left them straight back and got a noise violation lol
 

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Emailed Scott, didn't want to call and take up his time since I wouldn't likely be buying anything from him. Looking online it appears that they use the Flomaster Hushpower which is too large a diameter to fit under the door of a Z.

 

I'm really torn on this one. I think the Spiral flow will help, but probably won't do it all on its own. I think any number of exhaust tip inserts would also help. Classic chambered mufflers would definitely work but they use pretty restrictive louvered cores. I know Super trapps would work, but I hate the idea behind them. I guess I have 6 months or so to figure it out. Going to go hit up some Cobra forums and see what they're doing.

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Nobody says side pipes need to be under the rocker panels. they fit under the driveshaft  just fine and with a turn-down diffuse noise off the track  surface as well.

 

I run a truck  glasspack that is 4" OD and almost 36" long right under the driveshaft, and it goes to the muffler out back. It's very quiet and no significant dyno impact compared to the 3" pipe I had back there before straight.

 

Putting the  can on the back has a noticeable effect, but I could go with something less restrictive I'm sure.It's quieter than stock with both mufflers in place.

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If it were under the car, wouldn't that make it an under pipe and not a side pipe? ;)

 

The header collector is just in front of the door, so it's not going underneath. Could do that if I had shorties and then a single pipe out to the sides, but that's not the case. I do think you're right that if it dumped under the car it would be fine, and it's probably the reflection of the sound off the side of the car that makes it a problem.

 

Have been looking at longer glasspacks as an option. Classic chambered mufflers have a good rep for sound with the cobra guys, so that's kind of the front runner in my mind right now, but if I put a longer pipe on then I'll have to change the jack point on the side of the car, which is a bummer.

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I hear some people have good results with helmholtz chambers. Some new cars even use them on the intake piping to quiet those down. They are supposed to be for drone, but was reading a post several months back where people said it quieted the car also,  apparently with no hp loss.

Edited by socorob

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You know, just a thought... you could route the exhaust dump into the cabin behind the seats.

 

It would probably make the car really, really quiet outside. You just wear helmet and plugs inside...

 

And you're getting sleepy....

 

Sleeeeeepy....

 

Probably works better on BMW, MB and VW's thoug

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