Hot quiet my Ansa.

Good question.

I have some theoretical ideals, but since I don't have a running car, no way to try any of them.

I think the biggest problem will be finding space to install.

I think the "Mind Train" cross over pipe would helped.

Ear plugs.

quote:

had to shift to a lower gear to avoid drone.

Next time, instead of pressing on the left pedal and moving the shifter, I would suggest you try just pressing on the right pedal. The drone will disappear and you will have saved yourself a step.



Larry

Thanks, Larry. BTW, I got the lights hooked up. Very nice.

Funny, I was just about to create a new thread when I saw this one...
My exhaust is loud and takes away some of the enjoyment, not much quieter with window open or closed. I recently drove back from the SAAC convention in mid-Ohio, 12 hour drive, over 700 miles and it took 18 hours for my ears to stop ringing..
So using David Bell's thread from the tech section in SpaceCity Pantera's, http://www.spacecitypanteras.com/techinfo/mufflers/ with a bit of reverse engineering.
I read about Acousta-fill Boa in some forums, mostly bikes.. http://www.saveguard.com/Downloads/acoustafil.PDF
http://bogiesreviews.webs.com/...uffler%20packing.pdf
I ordered 3 bags of Boa. In the US they do not sell the mat but in the end because of the muffler's small size, the Boa worked out best.
I tried measuring the db of my car before I started with an iPhone app but it kept maxing out at 110db and it would not read higher.
My GTS Ansa muffler cut open with a 2.5" v-band pipe welded on to match up to my Pat Mical headers and pipes.
The "washer" that was at the end of the perforated inlet pipe had been previously removed.
My Ansa GTS muffler is quieter than a stainless muffler that I had tried previously. That was straight through and the fibre-glass matting just kept being blown out, junk. I wanted the stock look and less deafening.

With the Boa being stuffed inside.. I drilled some of the perforated pipe holes to 3/16", some were filled with carbon. I decided to not put anything in the final chamber where the 2 tail pipes exit, as the end of the pipe was open and the Boa would have just blown out. I can weld some mesh in there if I feel that is still necessary.

Fully loaded with Boa. In each bag are 4 lengths, I used 1 in that first section / inlet chamber. 1 and 1/2 lengths of Boa in the middle section.

Fully welded up.
The second muffler I did not cut open the final chamber.
The exhaust is certainly quieter, at 70 mph it is pretty good with the windows up. When I arrived back home, my family mentioned they did not hear the car coming down the road, only when it was in my driveway.
The droning is still there but not so loud.
Not sure if I noticed any hp drop on my short drive, my 393cuin makes 640hp, a stock 351 should make less noise.
I will run as is for a while and see if it does get quieter as they say, I did smell the coating being burnt off during my drive, no Boa is poking through the holes in the muffler.
If I do feel the need to make it quieter, I will weld some mesh, maybe the stuff you see on my bench in some of the pictures, and put in some Boa in that section.

I'm no acoustical engineer, but in my mind the droning could be coming from the last chamber. I know when I drive with the passenger window down at a specific height it starts to oscillate. By moving the window up or down it goes away. So maybe a baffle in the last chamber on one side or the other might counter act that. Inquiring minds want know.
Ken

"helmholtz resonator"

Thanks. This is great info. I might have to have the same done to mine.

So I decided to modify my muffler further as the resonation was still present. It was better and everyone said it was quieter. I purchased a perforated stainless sheet and went about modifying the final "chamber". Before picture.

The first muffler I modified I cut out as much of the perforated pipes as I could. This resulted in more of a straight through system when you look through the inlet pipe. I did not want more noise so I cut the muffler you see here with the inlet pipe at the point where it merges to the solid piece. Welding was not easy as the sheet was quite thin but I wanted to make sure it did not break loose.

The view through the inlet pipe.

"Boa" wadding installed and all welded up. The result is the resonation is now just very slight at 2,000 rpm, so much better than before I started these mods and quite a bit better than the mod of the 2 chambers.. The exhaust note is slightly different, a bit more of a deeper rasp, sounds good. It is certainly not a "stealth" car but it quieter than it has ever been. Your results will vary, smaller dia pipes, lower duration cam, lower compression, etc..

Great stuff! Thank you bdud for posting your project. Good to know!

yea, thanks
make sure, is this what you now have?

Yes that is how they are now. The area outside the perforated tube is packed with Acosta-fill Boa.

I did the hooker/cherry bomb mod in the sticky and I love it. Not bad at all OTR.