Quieting an Exhaust

Folks, I could use some help here.

I'm trying to determine what options are available to me to quiet my exhaust system. I recently added mufflers to my car and it is just slightly too loud in the cabin for my liking. I am liking the additional MAFv and load generated over the stock mufflers, so I 'd like to find a way to make this work.

The current setup is:

3" Lachute catted DP

3" Perrin mid/y pipes

2.5" AVO mufflers.

 

I'm considering dynamat of the trunk (sedan). I've also seen a slip in baffle used on some marine systems; may try one of these in the midpipe before the resonator. Has anyone tried something similar? Am I missing any other options?

Did the parametric improvements you mention occur solely due to the addition of the mufflers or did they occur when you changed more than one exhaust component?

I'd try a resonator in the mid-pipe.

^ don't Perrin's have one already?

Did the parametric improvements you mention occur solely due to the addition of the mufflers or did they occur when you changed more than one exhaust component?

 

Only one component. With a 20G and TMIC, I'm picking up ~0.25 g/cyl/sec load and 0.05v-0.10v MAFv on the new mufflers vs. the same setup with the old mufflers. The gain is bigger than the AVO intake, which I estimated at 10hp. I still need to try the full exhaust + intake over the weekend to see if there is a higher combined effect.

^ don't Perrin's have one already?

 

Correct, already have a resonator in the Perrin pipe.

Larger diameter resonator or larger diameter mufflers. There is no magic way to get more flow and less noise.

Did you check out Boostjunkie's dyno charts showing the effect of noise silencers?

 

He showed a fairly small performance hit from 2" silencers.

Go back to the stock cans, you'll chase your tail trying for more flow and less noise. Cats are the biggest sound reducers on the car, you have only a tiny one in your DP. Mufflers lower the tone, resonators can change the tone and lower a bit.

I think eventually I'm going to be back to the stock mufflers and intake. I just wanted to be absolutely sure I new how much HP I'm leaving on the table. Something inherent about being an engineer, once I get my cars tuned right where I want them I start getting the itch to swap something else to see the effect. Hopefully I won't take too much of a bath on resale of the parts.

Got ahold of a Radio Shack dB meter and took a few numbers.

 

At warm idle from 3 ft behind the car, the stock mufflers showed 89 dB compared to 96 from the AVO. Inside the car the difference was similar (78 vs. 88). At 50-60 mph in 5th (loudest steady state cruise) the difference in the car was 90 dB vs. 99 dB.

 

For comparison, my wife's stock FXT was 84 dB from the mufflers at idle and 71 dB inside the cabin.