I'm in the process of re-doing my exhaust. I wanted to go 2.75" straight back off the header. I'm not going to have any street/emissions products to stand in the way of flow, so the question remains. What have you done to make your exhaust lower/at the 95 db sound level- I'm thinking about Sears Point's rule here...
My original thoughts were to run two resonators backwards, and then get a 3.5" in/out muffler. Thoughts/Suggestions?

 

Try looking into longer mufflers like tanabe it will not be much quieter but it will be deeper . Maybe knowone will notice

 

any other suggestions?

 

The quietest cars I hear usually have the biggest cans - fine, if you've got the space.

Magnaflow has a pack with the perf tube formed into an "S" - you can't see straight thru it. Heard they work pretty good.

If you can go all the way to the back you might look into the Pete Weber Quiet-Muff. They Really work, and are reputed to be horsepower friendly.

Scott, who thinks someday we will probably all be quieter...it's not the end of the world.

 

I typically use a 2.5 inch straight through on the CRX racecars and a cheap 2.5 inch Dynomax straight through bullet style muffler and that knocks the D16A6 down to about 92 db depending on weather conditions.

If you could have dyno access, the bes thing to do is try some set-ups. A friend of mine is the OE exhaust engineer for Bosal Exhaust and he races a very fast ITS Olds Calais (wins most of his races in CenDiv). We tend to ask a lot of questions of him and his normal response it that many intuitive designs don't prove out on the dyno and some surprising ones do. His Calais is one of the quietest cars at Mid-Ohio but he says he has developed his system to be the most powerful option he can come up with. No need to be super loud if that isn't the most power. I hope to do some real exhaust tuning with him once things get going.

 

Two words.... Supertrapp. Maybe that's only one word

I'm told my car is really loud with the Supertrapp completely uncorked. Putting the right amount of disks in makes all the difference. I have pipe all the way out the back with no other resonators besides the 17" Supertrapp at the end. I make the most peak HP with it uncorked, but only 1HP better than with 12 disks in. I loose almost 3 more HP with 8 disks in, but it's quiet enough to run just about anywhere.

$.02

 

Speaking of things going "down" - what about weight?

I've got a Magnaflow and a Dr. Gas and together with all the flanges I used the whole thing weighs a ton. Granted it's placement is low, but it still sucks.

My local rules require me to exit within 3 inches of the perimeter view from above. If you can get down to where you need to be with a pack in the tunnel, that's hard to beat.

The ground clearance thing is a big deal to me - maybe to you too. It's hard to make one 3.5 - 4 inch pack in the tunnel do the whole job.

Dr Gas is supposed to be making a muffled boom tube (1.5 inches tall). You might be able to use one of those as a final and bring it out in front of the right rear tire.

Scott, who has to do some time on the dyno this winter too...

 

that's an idea... I've not really thought about clearance issues much. I was primarily going for velocity and the least restriction I could muster.... though you all have made good points. I'm not thinking that a 4whp loss is going to make a difference between first and second for me right now, so I may just go with something as suggested. The exit before the rear tire sounds like an interesting place for an exit... I will have to look into that farther.

 

Thats my setup. I put it together before road atlanta.. I was SHOCKED! I was @ 87db all weekend! Its a 2.5" pipe going thru a dynomax 9" round can. It tucks neatly up in my crx and doesnt hang low.. A Kck *** setup and yes its a straight thru design. Manufacturer claims 0hp loss as well!