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Discussion Starter · #1 ·
So it's an ongoing battle with our little cars. They're small, but they're pretty loud... The short exhaust run, high redline, and our constant desire to shed weight don't help matters. Our tracks up here in the northeast are getting stricter as complaints from neighbors increase.

I've finally come to a compromised solution that I think I can use for awhile. So I wanted to share it in case anyone is having similar issues.

I have the DMC header and running a decat pipe. From my understanding we'd burn right through the cat with track usage...and my car is basically a track car at this point. I also was advised to keep my muffler a straight-thru muffler with my power levels being what they are. My solution is to use a BOE ST muffler on unrestricted or less restrictive tracks. And to piggyback a BOE QS muffler on the more restrictive days. This setup just helped me pass a track that supposedly measures at 92db from 50ft away. Whether or not I was actually that low, or if I just wasn't loud enough to grab their attention is yet to be determined.

The swap between the setup can be done in less than 10 minutes and without removing any other parts really. I did remove my license plate and the two little lights that shine on it. You basically remove the tip off the ST muffler. Install the new u-bend that has a donut gasket (this was important to allow the muffler to move as needed), install the QS muffler with a rigid connection (and it fits perfectly) and then add your tip back on the end of the QS.

See photos. I know others have done similar...I just really like how this turned out since I can do the swap so easily...and it still looks somewhat clean to me. I was even able to fit my license plate back on it. BOE fabbed up the u-bend and brackets for me.

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Discussion Starter · #3 ·
That seems a pretty elegant solution.

Don't they make a phone app for SPL you could test it out on?
Yea there are. Although I'm sure there's so many factors that go into sound testing. One of them being how much dust and dirt build up I just have in my phone's mic haha.

Losing your day due to sound restrictions is just horrible though. Glad I have a fairly easy and quick solution now. Even further, I can eventually add a 90 or two and turn the pipe away from the corner workers that measure.
 

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Looks fantastic. I'm wondering how much heat the second muffler will throw and if you'll have any discoloring issues on the clam. Also, if you'll melt your license plate lights (been there)

I'm looking for quieter, because of local tracks (Laguna) and I like my hearing.

Thanks in advance for the follow up.
 

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Discussion Starter · #5 ·
Looks fantastic. I'm wondering how much heat the second muffler will throw and if you'll have any discoloring issues on the clam. Also, if you'll melt your license plate lights (been there)

I'm looking for quieter, because of local tracks (Laguna) and I like my hearing.

Thanks in advance for the follow up.
Only one hpde event under my belt. (7) 20ish minute sessions. I had the same concerns as you about the heat. I preemptively removed my license plate lights.

I actually took a little bit off my decat pipe to get everything further to the left as my initial install was way too close to the rear clam. See photo below.

My biggest concern was the u bend. It gets extremely hot and it's not insulated. At least the muffler itself has 3 layers of fiberglass. I also preemptively brought some titanium heat wrap with me to wrap the u bend just in case. I monitored it and everything seemed ok. I was new to the track and new to the power levels of the car... So I wasn't necessarily going balls out for 20 minutes straight. Data showed a lot more coasting than I'd usually have. I also thought about wrapping the muffler itself. That of course would keep heat in and likely blow out the fiberglass packing a lot sooner than normal. Although fiberglass packing is a lot cheaper than a fiberglass clamshell.

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Ran the dual muffler in series at Laguna for years. No issues with clam melting or anything, but depends on your clearance. Can also add some gold foil for a little extra shielding.
 

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Ran the dual muffler in series at Laguna for years. No issues with clam melting or anything, but depends on your clearance. Can also add some gold foil for a little extra shielding.
@acslater - I believe you invented this (on the West Coast at least, haha) ...

I have done exactly what @acslater did:

ST + QS and bolt the QS to the diffuser with an OEM hanger setup (rubber isolators and all, although we use only one nut and and bolt and one isolator per side)

We did not use a donut and likely a larger radius u-bend (I do not think the exhaust moves much because the hanger is bolted to the subframe?)
 

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Oh yea, I use a Difflow Railer-JR (and I keep my old TX plate for nostalgia reasons and it did not burn up)


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Great topic!
I use a ST-5 with a small U bend tip, and that passes Laguna 90 db days. No cat, 2.5" header
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Great topic!
I use a ST-5 with a small U bend tip, and that passes Laguna 90 db days. No cat, 2.5" header View attachment 1289751
In my experience, in an S220, running just a u-bend WITH a cat and stock header was hit or miss. ST-5 isn’t recommended for regular track use (per BOE) but is probably okay on an NA or OE supercharged Exige and might be enough to keep you under 90 more consistently… not sure how much variance you’ve seen in ambient conditions with your experience thus far
 

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In my experience, in an S220, running just a u-bend WITH a cat and stock header was hit or miss. ST-5 isn’t recommended for regular track use (per BOE) but is probably okay on an NA or OE supercharged Exige and might be enough to keep you under 90 more consistently… not sure how much variance you’ve seen in ambient conditions with your experience thus far
I’m running NA indeed, and used that setup maybe 10 times in various condition at Laguna without issue. Only time I got flagged was without the U bend (92.1db)
Funny I always thought the ST-5 was especially designed to pass sound at restrictive tracks, and not really recommended for street usage.
From BOE site :
“The ST-5 is engineered specifically to attenuate a few more dB at sound restricted tracks (Some will refer to this muffler as the Laguna muffler). It is not straight-through and will possibly sacrifice a few horsepower on forced inducted cars in exchange for approximately 5 more decibels of sound attenuation. We would typically not recommend this muffler for street use as it will require a little more regular maintenance due to internal complexity”
 

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Thoughts on a down bend after the last muffler if needed? get the exit pointing down towards the ground sorta style
 

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I’m running NA indeed, and used that setup maybe 10 times in various condition at Laguna without issue. Only time I got flagged was without the U bend (92.1db)
Funny I always thought the ST-5 was especially designed to pass sound at restrictive tracks, and not really recommended for street usage.
From BOE site :
“The ST-5 is engineered specifically to attenuate a few more dB at sound restricted tracks (Some will refer to this muffler as the Laguna muffler). It is not straight-through and will possibly sacrifice a few horsepower on forced inducted cars in exchange for approximately 5 more decibels of sound attenuation. We would typically not recommend this muffler for street use as it will require a little more regular maintenance due to internal complexity”
Weather conditions can play a big part of meeting sound. Heavy overcast or fog reflects the sound back down to the ground. Other noise from your car such as induction noise, even gearbox noise will add to the sound produced by your car.
 

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I’m running NA indeed, and used that setup maybe 10 times in various condition at Laguna without issue. Only time I got flagged was without the U bend (92.1db)
Funny I always thought the ST-5 was especially designed to pass sound at restrictive tracks, and not really recommended for street usage.
From BOE site :
“The ST-5 is engineered specifically to attenuate a few more dB at sound restricted tracks (Some will refer to this muffler as the Laguna muffler). It is not straight-through and will possibly sacrifice a few horsepower on forced inducted cars in exchange for approximately 5 more decibels of sound attenuation. We would typically not recommend this muffler for street use as it will require a little more regular maintenance due to internal complexity”
Yes, I should clarify I was at 350 whp and IIRC it was actually not recommended for that much power - street or track. I conflated my circumstances with what the general usage is for the muffler, my mistake.
 

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Discussion Starter · #15 ·
So with that slash tip that comes with those BOE mufflers, I can simply loosen the clamp holding the tip and turn it 90 degrees downward to point at the ground. I was ready for that in case I got flagged. But all went well this past Sunday.
 

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Discussion Starter · #16 ·
Yes, I should clarify I was at 350 whp and IIRC it was actually not recommended for that much power - street or track. I conflated my circumstances with what the general usage is for the muffler, my mistake.
So from what I was told about the st-5. The packing will wear out really fast. But there's also weld points inside the 2 stage muffler design that the heat from the the boosted cars can possibly break down. Then a rebuild isn't simply repacking with fiberglass but also re-welding the interior bits. Horsepower loss was not huge for me. Something like 325 down to 320... Only in the last 500rpm or so.
 

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Does the stock exhaust meet sound regulations?
Maybe it could be re-plumbed to exit above the diffuser.
The weight of two canister style mufflers may weight more
than the OEM boat anchor. Also, the OEM does not have packing
material. It is a chambered design....
Before I went down the modification hole I thought the stock
exhaust wasn't bad. I swapped it primarily for weight savings.

The Sonic Fury from Inokinetic may meet sound regs alone.
It claims to not drone but it does however significantly less than
any exhaust I have ever used and I have been through many.
 

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Discussion Starter · #18 ·
Does the stock exhaust meet sound regulations?
Maybe it could be re-plumbed to exit above the diffuser.
The weight of two canister style mufflers may weight more
than the OEM boat anchor. Also, the OEM does not have packing
material. It is a chambered design....
Before I went down the modification hole I thought the stock
exhaust wasn't bad. I swapped it primarily for weight savings.

The Sonic Fury from Inokinetic may meet sound regs alone.
It claims to not drone but it does however significantly less than
any exhaust I have ever used and I have been through many.
Yea the basic stock one would likely meet sound regulations. Not the stage 2 or others. I think the two mufflers are actually still lighter. The benefit of the two mufflers is the straight through design for higher horsepower setups. And the swap is really easy now. I can go to an unknown track with the single muffler and tack on the 2nd muffler if I get warned.

The drone is one thing. But the high pitch noise that comes out of the 2zz at near redline is what was triggering most of my issues with getting flagged at these events. With all that said, I don't particularly like the sound of these boe mufflers... But I don't really care for all that anymore.
 

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Another data point, I have 2bular headers, mid-pipe with silencer, and 8x22 muffler, with stock intake (no "boot") and SC pulley (basically stock S240 power). This setup has been fine a number of days at Lime Rock, Tremblant, and Club Motorsports. I did get a warning once at Tremblant on an overcast day with a low ceiling, no black flag but they warned me on my way in that I was "marginal". They move their sound meter around which may also have been a factor. Sound-wise, the mid-pipe with silencer falls somewhere between a straight mid-pipe and a mid-pipe with high flow cat, I think it's a good option if you just want to have one setup.
 
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