need help w/-110dB Road Race exhaust system 13B n/a bridgeport

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the problem is that I have to get my car down to 110 decibels.
my car now is 113.

my car is a FD brdigeport n/a
I dyno before doing the mod's @225whp and 147torq

I have the "long" exhaust system. RB road race header and I continue both primaries tubes independent til the diferential then the Y collector and megaphone then a Dynomax 3 1/2'' muffler.

since I have to drop bellow the 110dB I got 2 Dynomax bullet muffler and installled them on each of the independent primaries.

I installed them parallel (same length from the header flange)

didn't do any changes and dyno again @216whp and 141 torq
the torq curve became a wave up-down-up-down and huge power drop at high RPM's

I talked to a friend and he said that the bullet muffles had to installed at a different lenghts (not parallel).

any ideas on this?

 

have you tried an angled tip on the exhaust? how about some kind of airbox, lots of noise from the intake too....

i don't know about the presilencer thing, might as well try it

 

Jose, your original setup was very similar to mine except that I run a Borla Race Muffler. I usually run between 102 and 105 db. What I do when I need to drop the decibles a bit lower, is run a Super Trapp off the end of the Borla. Not the best for restriction, but with the adjustablility of all the discs, you can really muffle the beast. It also gives off great flame patterns on over runs, LOL. I have also used a single 3" turn down off the end of the muffler to point the exhaust at the ground. This also works very well and has almost no impact on power.

Another thing I found was that the gauge of exhaust pipe makes a strong difference in sound levels. The thicker the gauge of metal reduced the tinnyness and keeps the car a lot quieter. I would also look at the intake side, as mentioned before. My car was very quiet, but after I added the 4 ITB's, all you can hear is intake noise as the car comes towards you. I need to create a muffled airbox now.

Eric

 

I did a short system about 16'' to the Y and the megaphone and 4'' till the end with 1 bullet and 1 muffler and was still 112db.

How does your inspector checks your db level?

 

our noise levels are all checked on track. at infineon there is a sound guy drivers left at turn 12, we are allowed 103DB there.

at laguna seca the sound guy is between turn 6 and 7, and it depends on the day, they are usually around 92db

if your test is different, then the DB numbers are going to be way different

 

Find out where they measure the sound level at your track (left or right side of the track) then add a 90 degree pipe at the back of your car aiming the exhaust away from the db meter. If you're at the track and are still having issues shift up a gear and/or lift a little when you're passing the db meter.
In the end, everybody has to meet sound so everybody takes a hit in the power when adding mufflers... so welcome to racing.