Muffler question: Resonance

pmajka · 11-05-2007, 05:45 PM

i just got the B&B headers on and used a Dynomax dual in dual out.

i plumbed it opposing flow, not head on tail out. but right bank goes in top and out top out left goes in bottom out bottom.
so its just about a true dual system.

it resonates between 1750 and 3000 rpm, like shattering teeth resonates.

over 3k, it sounds sweeeeet.

if i put cats (have to) on after the muffler (so on the tail of the exhaust path) will it quiet down the resonance....or

do i have to put cats on before the exhaust gets to the muffler.

sorry no pics yet...
tomorrow.
Oh...butt dyno says WOOHOO.

Zeke · 11-05-2007, 06:03 PM

I don't see how you would put cats on after the muffler. Besides, cats need the heat. I think dual cats would be good for flow and equalization. I've looked at mine a few times with that in mind. But, I'd need to see a pic of what you have so far.

PatrickB · PatrickB's Garage

Which model number Dynomax did you get?
I just picked up the #17276 Ultra Flow Stainless 2 in/2 out.
Post a picture if you can, as I'd love to see how it looks from the back and underneath!

Thanks!

pmajka · 11-05-2007, 06:51 PM

here is a diagram, very rough...

cats will be after the muffler in flow.....

pmajka · 11-05-2007, 07:07 PM

sorry for closeups..but, wife is asleep, cant open garage door.

Lower bumper cover is not on yet...

mb911 · mb911's Garage

I think Tip angle has allot to do with it. The noise is bouncing off of the ground..

Mike Stanko · 11-06-2007, 02:03 PM

pmajka,

Common problem. I can relate.

I have B&B headers + their 2 out muffler on an '83 SC. Acoustical resonance occurs 2000 - 3000 rpm. It's pretty tiresome and a grind on a long trip. Like you, above 3000 rpm, all is great. I called B&B. They said to cap/plug the right side out to eliminate the drone. Cost is a couple hp according to them. I've seen others post that they believe the penalty is 7 hp.

Mike

pmajka · 11-06-2007, 02:08 PM

ok, the dynomax muffler is a parallel tubed muffler, with perferated holes, if i cap one end , the HOT gasses, of one bank, will transverse through the sound deadening material to escape the muffler,

Is that a bad thing or do people do this every day?

pmajka · 11-06-2007, 02:36 PM

Zeke · 11-07-2007, 05:35 PM

I'm sorry, but how can you live with one pipe one way and the other...oh, never mind.

I talked with mb911 (Ben) today and the angle DOES have something to do with it. This guy makes all kinds of mufflers including ones for small aircraft.

Scott R · Scott R's Garage

Quote:

Originally Posted by milt

I'm sorry, but how can you live with one pipe one way and the other...oh, never mind.

I talked with mb911 (Ben) today and the angle DOES have something to do with it. This guy makes all kinds of mufflers including ones for small aircraft.

I have to second this, Ben created a custom muffler for a few of us, now called the "Gen 4" and it gets rid of the resonance issue. I'm sure he can help here as well.

PatrickB · PatrickB's Garage

Quote:

Originally Posted by Scott R

I have to second this, Ben created a custom muffler for a few of us, now called the "Gen 4" and it gets rid of the resonance issue. I'm sure he can help here as well.

Scott~

Can you share a picture of the "Gen 4" Muffler?? Is the exit pipe(s) perpendicular to the ground, or is there some interior design difference compared to Ben's earlier mufflers?

pmajka · 11-08-2007, 03:40 AM

well the muffler is not quite done, notice the left side has a coupling as its final extension. eventually i need to get cats on there, but with the B&B headers , its really tight. I also did all the piping at 2.5".

the left bank might need some custom bending from my Muffy Man. then they will both go straight out the back.

If that fails, i have and X-Pipe idea for cats and resonators.

can anyone tell me the part number for the 2 in 1 out muffler (magnaflow or dynomax)

Off to D.E.