View Full Version : Failed sound level check at Autox


z28bryan
04-22-2007, 09:20 PM
Well I need to do something to quiet my exhaust down slightly. I was at 97.something on the decibal meter at the 75 foot away mark. In my local club I need to be under 95. I think its even lower for the NER club and I know they would toss me.

I've only had 3 different setups. 1 was stock, 2 was the corsa exhaust, 3 is what I have now:
Kooks LT's with high flow catted ypipe
corsa catback
avg cam 224/228 .560/.570... something on those lines

So I'm not sure exactly what would be the best balance between not losing too much power yet keeping the sound down. Maybe I only need to toss on an exhaust tip that points downward?

I figured a lot of you guys have heard and compared different setups, especially Slowhawk and crew

ps... I'm f*in pumped because the sox just hit 4 solo hr's in a row from the point where I began typing this until when I posted this thread, lol, completely sick

ace68
04-22-2007, 09:56 PM
that was sweet go SOX"S

Ojustracing
04-22-2007, 10:05 PM
Hey Bryan why not stick a bullet style muffler in the I-pipe. I ran Mac-mids, ory, moroso Sprial flow, and GMMG at Lime Rock and didnt get tossed. If you are looking for it to be toned down a little a a regular bullet muffler should do the trick if you are looking for a bigger noise reduction the sprial flow would be the ticket.

John

z28bryan
04-23-2007, 10:34 AM
Yeah I think the mids help you out there. I have longtubes. I may consider mids, even if it puts me down about 20 horse. Maybe a cutout for the speedway events, with a quiet exhaust closed during autox.

I'm wondering if doing all this will mess up my A/F ratio and will need to be retuned

BlackScreaminMachine
04-23-2007, 10:49 AM
Thats weird, I have a corsa, LT's with dynatech catted Y pipe, my car is a lil louder then stock, its nothing crazy. I think your highflow is looser then most.

z28bryan
04-23-2007, 10:56 AM
I have a cam too though. If you had a cam, you would be a bit louder depending on how big it is.

davered00ss
04-23-2007, 10:57 AM
Go with an SLP Dual Dual cat-back. Flows prety good and probably the quietest cat-back you can put on.

Slowhawk
04-23-2007, 11:52 AM
I agree with Dave. You can try a Magnaflow that is cheaper.Should be quieter than what you got.If all else just throw a bullit on there too.

Forget the midlengths.You have nice headers already.

What some people don't understand is when you add a H/C setup with raised compression the exhaust will get louder and change tone.I hated my Corsa after doing a H/C setup.

BlackScreaminMachine
04-23-2007, 12:05 PM
Welp, I know nothing about the car aside from the post, never saw head work of any sort and saw a small cam. I know tone changes. I know the diff of a corsa with cats and without. My 383 was tooooo loud with no cats and a small hotcam. As for Db level, I would think its how well the cats were working to deaden the sound.

Stock cam, stock heads, with a new catted Y I can honestly say its louder but close to stock.

Eitherway, I hope it gets fixed soon so you can run.

z28bryan
04-23-2007, 02:08 PM
I agree with Dave. You can try a Magnaflow that is cheaper.Should be quieter than what you got.If all else just throw a bullit on there too.

Forget the midlengths.You have nice headers already.

What some people don't understand is when you add a H/C setup with raised compression the exhaust will get louder and change tone.I hated my Corsa after doing a H/C setup.

That sounds like a good solution. If the slp dual dual is quieter, I'll get that over the Magnaflow. Where does the bullit go, between the cats and muffler?

The Corsa performs a pretty obnoxious exhaust belch when you lift the gas after WOT with my cam. Lots of people think its cool, but it gets annoying after a while.

Bowtie Boy
04-23-2007, 02:34 PM
http://store.summitracing.com/partdetail.asp?autofilter=1&part=DTC%2D72%2D32520&N=700+305162+115&autoview=sku

Sound reducer cones for headers/mufflers. There is little or no power loss from these.

ace68
04-23-2007, 06:14 PM
I used the cones they didn't cut me back too bad and did work.

badpewter-z
04-23-2007, 07:32 PM
dual/dual quiet and doesnt hurt power to much untill you start pushing ALOT of compression and power but still quiet :)

Zturd
04-24-2007, 07:18 AM
Just a shot in the dark but something i considered doing to the vette cause its to loud and may help you anyways. Borla has the plate system with reduced size holes in it. They are just a thin sheet of metal that you could put in where your catback comes together somewhere and it would be like a gasket and a smaller size hole. Giving you mroe torque but making the car much quieter and cheap easy in and out??? Just a shot in the dark.

z28bryan
04-24-2007, 08:27 AM
Can you still buy the dual dual these days?

iamsickofitall
04-24-2007, 08:51 AM
Can you still buy the dual dual these days?

only used ones

davered00ss
04-24-2007, 09:06 PM
SLP doesn't sell them anymore?

iamsickofitall
04-24-2007, 09:29 PM
SLP doesn't sell them anymore?

nope, they stopped sometime last summer. when i was looking for one, SLP said speed inc. was pretty much the only shot i had at getting one that might be sitting on a warehouse shelf somewhere, but they were sold out when i called. i just ended up getting a used one from a friend.

F-Bobby
04-24-2007, 10:56 PM
wtf they have a limit as to how loud you can be on autox? i guess im never going to one my car wakes the dead.

z28bryan
04-25-2007, 10:32 AM
wtf they have a limit as to how loud you can be on autox? i guess im never going to one my car wakes the dead.

Some of the residents around Devin's complain I guess. Go figure, what were they thinking when they moved next to a military base and airfield?

In any case, my exhaust is annoying the hell out of me so fixing this is also something I want to do for my ears.

So say I went the Magnaflow/bullet approach how does that get setup? I looked up bullet mufflers and saw that there's two loudmouth types. Would this setup be like combining a Magnaflow and Loudmouth exhaust together? Doesn't the Loudmouth resonators go between the rear axle and the y-pipe?

BillS
04-25-2007, 11:30 AM
I race with the NER and had to comply with the sound rules. My ATR system did not make it. I tried the cones and they did nothing. Directing a turndown away from the meter worked untill the officals wised up and moved the meter a few times during the event. I added an 18 in dynomax bullet muffler in the int pipe after the cat/ypipe and that got me below sound.
The SCCA will be implementing a nation wide sound limit sonn because they are losing sites to noise complaints, NER is stricter, and its even worse if you run up at NHIS

mcG
04-25-2007, 11:53 AM
do you guys think a basicly stock ls1 with slp loudmouth 1 exhaust would fail?

z28bryan
04-25-2007, 01:06 PM
I race with the NER and had to comply with the sound rules. My ATR system did not make it. I tried the cones and they did nothing. Directing a turndown away from the meter worked untill the officals wised up and moved the meter a few times during the event. I added an 18 in dynomax bullet muffler in the int pipe after the cat/ypipe and that got me below sound.
The SCCA will be implementing a nation wide sound limit sonn because they are losing sites to noise complaints, NER is stricter, and its even worse if you run up at NHIS

Yeah I definitely don't want to squeeze by the 95 db limit. I've never gone to the NER events. I'm well known at the BMWCCA ones, so they are easier on me. Id rather clear it by a bit.

So I am on the right track about tossing the bullet on the intermediate pipe. They told me I could put a tip that is turned down, but I didn't see how that would help a lot. It's not really fixing the problem

BillS
04-25-2007, 02:45 PM
Yea any car with the loudmouth will fail. I have seen stock Z06 and lotus' fail sound. I have even seen a guy get failed because he hit his horn by accident in a turn .

z28bryan
04-26-2007, 10:31 AM
I'd like to try the SLP dual/dual with one of those Dynomax bullets in the intermediate pipe to see how that works.

Now, if I could get my hands on any type of SLP non loudmouth setup... anyone know of anyone selling one locally?

Other options I've looked up on random searches were the Hooker muffler. That got some good reviews for being quiet, but again its random people on the forums and I can't always rely on them.

BillS
04-26-2007, 11:12 AM
My car came with a dual-dual and it was super quiet. I switched to a LM1 and it was fine untill the headers and motor work. I switched the the ATR and I liked it but was over the limit, Adding the 18in bullet worked fine. You very well might be fine with just a dual-dual if you can get one. I still have mine and am not letting it go.
Also were you the white camaro at the evo school? If so I saw you, I was there in my wifes WRX, autoxing in the snow sucks on V710's. If that was you, you are loud, there were a few comments about it over in the challenge school

Slowhawk
04-26-2007, 11:52 AM
Hooker sucks and will not pass.

Listen :judge:

All you need is a SLP dual/dual -no bullit

or a Magnaflow with a bullit

Kids never listen do they? :jest:

z28bryan
04-26-2007, 11:55 AM
My car came with a dual-dual and it was super quiet. I switched to a LM1 and it was fine untill the headers and motor work. I switched the the ATR and I liked it but was over the limit, Adding the 18in bullet worked fine. You very well might be fine with just a dual-dual if you can get one. I still have mine and am not letting it go.
Also were you the white camaro at the evo school? If so I saw you, I was there in my wifes WRX, autoxing in the snow sucks on V710's. If that was you, you are loud, there were a few comments about it over in the challenge school

Yes that was me :) That was a pretty rough day. I'm currently probably the loudest car I've ever heard at an autox event. I get a lot of compliments, but it's def not going to stay that way, lol

z28bryan
04-26-2007, 12:05 PM
Hooker sucks and will not pass.

Listen :judge:

All you need is a SLP dual/dual -no bullit

or a Magnaflow with a bullit

Kids never listen do they? :jest:

There it is again. Random people on the internet making suggestions :jest:

So I'll make sure I pick up the Hooker, run mac mids, and swap my cam out for a 210/214 .630/.654 with a 124 LSA...

seriously though that definitely helps. The search is on for a dual/dual

badpewter-z
04-26-2007, 02:03 PM
dual/dual requires no bullit its already piss quiet :judge: