How many of you guys regret taking off your resonator/muffler?

[dparm1984]

If you want better flow quality without going deaf, go for a bigger (more volume) resonator. More volume typically equates to more sound deadening, it's as simple as that.

 

[MSMS3]

Yes. Completely right. The reso will be a straight through design. You can look in one end and see daylight out the other. What makes it work is small holes in the pipe inside the resonator and then sound deadening material outside the pipe and inside the outer shell. The better the material and the more of it there is, the more effective the sound reduction without affecting the flow volume.

Depending on where you want to put the reso, there is limited space under our cars for anything REALLY BIG. The one I selected was welded in place in the middle of the race pipe because there was room there which had been taken up by the second cat. An oval shaped reso there will be wider but thinner. The width was no problem. But it had to be relatively thin, because there is a cross-member there where there was potential for interference.

I say use the biggest one that will fit. There are a number of companies that make good ones. The 3 inch Vibrant Ultra Quiet seemed the best fit for the construction and sound deadening material I was looking for. There are other good ones out there too.

 

[MSMS3]

O.K. so here is an mp3 exhaust clip.

This was made this morning. It represents normal stop and go driving over a period of about two minutes. There are a couple run ups to 6000 rpm through 1st and 2nd gear and a couple of slow downs in gear taking it back down through the 2000-3000 rpm range where there would normally be drone.

For the obsessive-compulsive, attention to detail and repeatability types among us:

The mike is very sensitive high quality. It is calibrated for high fidelity use. It is attached to a commercial grade Olympus DS-4000 digital recorder. The mike was placed in a fixed position on the right front passenger seat. Base of the mike was pushed between the seat back and seat bottom so that the mike was pointed up at about a 45 degree angle and could not move.

The windows were UP, so as to give a sense of what it is like to drive the car daily for commuting on public streets.

Draw your own conclusions. You can turn your volume up or down and make it sound as loud and soft as you want. But you will notice that you can hear the engine as well as the exhaust and that the exhaust tone is very deep pitched, gurgling, kind of like Flowmasters on a muscle car, and that drone is practically gone. That was my objective.

I do have a calibrated decibel meter and can accurately measure db volume inside or outside the car. However, unless you are being very exact about mike placement, this becomes pretty meaningless.