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Old 05-30-2012, 12:22 PM   #1
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I have been ringing the bell on the sound meter at Thunderhill at 107db. I need to get it under 103db. I currently have a 4" round 2.5"x14" magnaflow. I have room to add another 4" round 6", 14" or 18" long muffler. I want to get under the limits but don't want to go too far and not be able to hear the car.

I am leaning towards the 14" but figured I would ask you guys first. I want to avoid doing it twice if possible.

Rotrex SC with RB header in case that makes a difference.
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Old 05-30-2012, 05:58 PM   #2
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The Magnaflow isn't a straight-through/glasspack-style unit, right?

I'd guess a 14" straight-through design would work. Minimal power loss too. Like thus (random jpg):

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Old 05-30-2012, 06:06 PM   #3
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The current 14" magnaflow is pretty much the same as the one you posted.
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Old 05-30-2012, 06:22 PM   #4
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Fair. I daren't guess then to be honest. I'd lean towards a 6", but it would suck if you still didn't get under 103db.



Edit: I don't know why I thought the existing muffler type made any difference… 107db is 107db. Also, is temporarily attaching the cheapest 6" straight-through muffler you can find to your existing exhaust at the next event an option? I think that trying to tread a really fine line between too loud and too quiet is a bit of a crapshoot without testing.

I'm really interested in this because I'll probably run into the same problem over here when I get mine on track.

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Old 05-30-2012, 06:53 PM   #5
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Put as much turbo muffler under the car as you humanly can. Think 22x11x5 Magnaflow. 107db is serious loud, if you can use a big muffler and get it down to ~97 you'll still be able to hear it just fine.
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Old 05-30-2012, 07:03 PM   #6
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Quote:
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Put as much turbo muffler under the car as you humanly can. Think 22x11x5 Magnaflow. 107db is serious loud, if you can use a big muffler and get it down to ~97 you'll still be able to hear it just fine.
Where the heck are you stuffing that thing? It's huge!

My current exhaust terminates at the diff. I would like to keep the same overall length to leave my options open for undertray work. I have room to add another 5" x 14" or 5" x 18" round can without changing the overall layout. Based on your suggestions I will try to fit that 18" muffler.
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Old 05-30-2012, 07:06 PM   #7
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Isn't a drive by 97db reading stock exhaust territory? Stock S2000s hit 98 on one track over here. Granted, the track undoubtably has very different measuring parameters.

In Thomas' car the wind and road noise must be massive, which is why I'm erring on the smaller muffler size if he still wants to hear it...
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Old 05-30-2012, 07:47 PM   #8
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Quote:
Originally Posted by k24madness View Post
Where the heck are you stuffing that thing? It's huge!

My current exhaust terminates at the diff.
That's your problem. The sound bounces to the ground and reflects onto the underside of your car like a guitar body. Try running it to the rear and then using a "pointable" turn to turn it away from the sound meter.

107! Darn, I just bought that same muffler! It looks like it's back to the Summit oonline order desk.
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Old 05-30-2012, 08:38 PM   #9
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I have a Magnaflow 3x14 that goes into a Flowmaster 3" 44 series. I have yet to get the dB level. But its not loud, has a nice sound to it I think. The Flowmaster has a turn down underneath the car, right before the rear diff.
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Old 05-30-2012, 10:35 PM   #10
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Quote:
Originally Posted by k24madness View Post
Where the heck are you stuffing that thing? It's huge!
I could fit two of them with a little creativity and some tight 3" bends. It's tucked up under the left side of the rear bumper, aiming left and slightly down. It's my Laguna exhaust - I blow ~97-98dB without it, and about 84db with it.
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Old 05-30-2012, 11:38 PM   #11
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22x11x5 crew signing in
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Old 05-31-2012, 01:58 AM   #12
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There is no such thing as too quiet.
With a supercharger, it will never be quiet.
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