How can I quiet my exhaust a little (for inspection)?

Failed my inspection at DEQ today due to the noise test. The drivers side registered 95.1 dB, and the passenger side registered 92.9 dB. The max allowable in OR is 93 dB.

My exhaust system is stock except for the Flowmaster muffler.

Is there any way I can quiet it down a little bit without making major modifications to the exhaust system? I don't have my stock muffler anymore, so I can't swap that back in.

Hmm, Good question, maybe someone here has a definate solution on what you can do, what comes to mind to me is my dads 23 ford t-bucket has zoomie headers basically look like a open long tube header, but they have removable baffles in the pipes, maybe you could find a baffle to add in just to pass inspection.

I have a very hard time believing that an LS1 (known for being quiet) is 95 and 92 dB. Are you measuring in A weight or C weight? Most vehicle testing (car magazines) is done in A weight. Rules have always to the best of my knowledge been in A weight.

My L98 with high flow cat and GMMG (one of the louder catbacks) registers at the following:

Car idling in park, outside, fully warmed up, closed loop. Decibel reader at waist level.

5 ft away: 92 dbC or 77 dbA
10 ft away: 88 dbC

My local rules dictate that gas powered cars should be no louder than 83dbA when measured at an inspection shop.

Another thing to keep in mind. My GMMG with cat is louder than the Flowmaster American Thunder was without the cat. There is no possible way than an LS1 with just an aftermarket muffler is failing the noise test.

I have a very hard time believing that an LS1 (known for being quiet) is 95 and 92 dB. Are you measuring in A weight or C weight? Most vehicle testing (car magazines) is done in A weight. Rules have always to the best of my knowledge been in A weight.

My L98 with high flow cat and GMMG (one of the louder catbacks) registers at the following:

Car idling in park, outside, fully warmed up, closed loop. Decibel reader at waist level.

5 ft away: 92 dbC or 77 dbA
10 ft away: 88 dbC

My local rules dictate that gas powered cars should be no louder than 83dbA when measured at an inspection shop.

Another thing to keep in mind. My GMMG with cat is louder than the Flowmaster American Thunder was without the cat. There is no possible way than an LS1 with just an aftermarket muffler is failing the noise test.

the test was performed at 2500 RPM.

noist test results at the bottom:

http://i142.photobucket.com/albums/r98/camaro322hp/CIMG1846.jpg

Hmm, Good question, maybe someone here has a definate solution on what you can do, what comes to mind to me is my dads 23 ford t-bucket has zoomie headers basically look like a open long tube header, but they have removable baffles in the pipes, maybe you could find a baffle to add in just to pass inspection.

thanks, i'll look into that. i was hoping to avoid welding....:cry:

oregan is the last place i want to live now that ive visited this thread

this is a little gay but, we used to use steel wool wadded up in the exhaust tips. it quieted the noise.

this is a little gay but, we used to use steel wool wadded up in the exhaust tips. it quieted the noise.


i thought about that, but he put the sniffer probes up the tail pipes last time. i'm thinking about maybe getting creative with my cutout opening, maybe i can jam something in there. just gotta be careful that it doesn't break lose and get lodged in the muffler.

look here it may help you out http://store.summitracing.com/egnsearch.asp?N=700+4294923429+4294922711+42948654 05+115+4294791510

Well, I guess the DEQ doesn't flag you for return visits. On my third trip through DEQ (I had some other SES problems), they passed me without doing a noise test. I think you just have to keep a soft foot on the gas and clutch as you pull into the inspection bay, as it seems to be totally at the tester's discretion whether or not to do a noise test.

But thanks for the suggestions everybody. Time to open up the cutout again.... ;)

I live in Portland. I hate having to go thru DEQ they are so strict here. I have the Borla exhaust so I just put in the solid restrictor plate and that solves the problem. When I went thru they said my exhaust was at 115db. Nice Z I have a lot of the same suspension mods as you do..

You could get freeze plugs the size of your tips, drill a 2.25" hole in them and pop them into the tips. If needed, pack a little steel wool behind.

Once you pass, it would be easily removed.

I live in CA and when I took my car to one smog place he did not even try to smog it. He said I have a cam and the exhaust was way to loud so he did not want to waste my time. But he did send me to this other guy that charged me $60 and did not say anything just passed me. Maybe you can find a smog guy that will overlook the noise.

Add a bullet muffler in the intermediate pipe just before the over axle bend. Generally, the more muffler volume you have, the quieter your exhaust will be.

Haha, I had the same exact problem, with my loudmouth + bullet muffler on I pipe, stock y pipe, cats, and exhaust manifolds. Except, I was already at 90 db at idle, and was at I believe 108 db at 2500 rpms..

Funny, I was going to do a flowmaster exhaust too, but the exhaust shop said even that was too loud (which I guess they are right!), and ended up with a Dynomax exhaust - which surprisngly sounds good. I needed something quick and cheap to get myself back on the road legally.. If I could do it again, I may consider a Borla with the plates.... But that would be like 3x the cost.

So you didn't get tested on your third try? Blah. :) I can see though though. I got tested twice before with this car, and that was my first time they did the noise check.