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?

 

Might want to try rotaflo mufflers...
http://www.rotaflo.com.au/

 

I really must find the video. A company called Anniversary Racing Factory dropped a similar FD down quite a bit with something they called a Swirl Silencer.

I don't make nearly the power you do, but 3 1/2" seems awfully large for the power output. The exhaust energy is a lot lower at the end of the system than at the engine, you can actually drop the size down quite a bit without losing power.

As an example, I have a 1 7/8" diameter restrictor at the end of a 2 1/2" exhaust system (zero baffles, two perf-core mufflers) and it cut noise quite a bit and 1/4mi elapsed times and trap speeds did not change one bit. Neither did AFRs across the board, indicating no discernible VE change. My engines never made more than ~210-215 at the crank, however. But the principle is the same.

 

I have been in racing for a while and this is always a challenge with a Rotary. What I see having the best luck is Borla, Magnaflo and the MFR Lava Rock mufflers. In that order. The Borlas have been in use on the Formula Mazdas on some pretty short systems and are straight through. The Magnaflos are only used at the very rear of the car as their thermal limit is not known around here. The mFR Lava Rock is a great choice, if you like the extra weight. I did my own and it worked, but added almost 30 lbs. But i made it so I could repack it too. The outer case is 11 gauge 304, 18" long and oval in shape. 3" in and out.

GD

 

should of just made it flange to the racing beat fd 3inch exhaust would've helped with sound definitely and probably some power

 

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?

 

florida doesnt have any inspection? or is it more a noise pollution fine u dont want to get?

 

Most racetracks have decibel limits, usually 104 or so. One place where I autocross has a 93db limit. Yes, only 93db.

 

I make 200+ rwhp on my EP 2nd gen with a large streeport. My system is an RB header merged after the flange to an expansion chamber, 3" back to a Magnaflow 4" filled with lavarock and a turn down that I turn away from the sound microphone. I get readings any where from 95-99 db typicall turning 8K plus past the sound location.

 

I made my own mufflers and also did a set for a customer's EP 2nd gen that worked AMAZINGLY. Somebody did a decent write-up for making some a while back, can't remember where or who did it tho... Larger body will cut lower frequency, but jam-packed fine packing material is what will cut the higher frequencies (usually what is so loud on rotaries).