Anyone running the Dynomax turbo mufflers?
I have the 2 1/2" x 19"lg. ones on my truck, with a stock 350.
The problem is that I wanted some cheap/good/quiet mufflers for my work truck,
so the Dynomax was it, but at/around idle (from 700 to about a 1000rpm) the exhaust
resinates pretty bad, but its nice and real quiet when above this - cruising rpm. The
exhaust is block huggers, 2 1/2" pipes to the mufs and dumps before the axle.
At first I thought that it was resinating under the bed, I got the bed off now (body work)
and it still does it. Any ideas on why? or what I can do to fix it?
Could it be the 19" lg mufs resinate and the shorter turbos dont?
Thanks

Any muffler will do that if you have it dump before the axle. Run some tailpipes and the resonation will dissapear.

I run the Summit turbo's on my mildly modified 1986 C10 with a 350, and there is no resonation anywhere, probably because I'm running tailpipes.

I run the Dynomax Super Turbo mufflers (Short) on my 69 Camaro and use Flowmaster exhaust to dump out the very back of the car. I have no resonating issues. Previously the car had dual 40 series Flowmasters dumping before the rear axle and it resonated like crazy

Internal resonance is a real problem with newer GM Trucks. We have been doing some testing on a new muffler that significantly reduces internal resonance. In the 6100 & 8100 series it Chasis Dyno tested to produce 25 additional HP! Problem is they are quite expensive.

67RS, shoot me an e-mail with your combination if you are interested.

I have the Dynomax Ultraflows which don't seem to produce any resonance except just off-idle.

Well I know that Flows would do that, but Dynomax turbos - I thought they would
be quiet all the time. We have a set of the short ones on my buddy's Chevelle and
it doesnt resinate at all. Later I do plan on stickin an X-pipe on it and maybe tailpipes.

He, He!!

I just gotta again!!

Glasspacks don't resonate, but they sure do that "Cop-calling? cackle thing!!

I know, I know, I'm lost in the '60's, He, He!!

pdq67

You might experiment with adding a hangar or two. Sympathetic vibrations might be tuned out if it is in the right frequency. Just a crazy cheap thing to try.

-Mark.

Originally posted by stingr69:
You might experiment with adding a hangar or two. Sympathetic vibrations might be tuned out if it is in the right frequency. Just a crazy cheap thing to try.

-Mark. Actually that's not crazy at all. The military uses strips of metals banded to pipes to eliminate hydraulic resonances. All you are trying to do is alter the pipe's resonant frequency to a pitch that is not excited by whatever is going through (or connected to) the pipe. For example, a pipe that is 20 feet long would be excited by a vibration that has a wavelength of 20'.

Not sure how it would work with an exhaust system, but the principle should be the same. One extra clamp in the middle of an exhaust pipe would double the resonant frequency. If the resonance is truly inside the muffler it probably wouldn't help.

All exhaust systems resonate at some point. A properly engineered and built system will not resonate within an engines normal operating range. Tailpipes affect the point where resonation occurs (I don't remember in which direction though). The problem with a truck is that the bed acts as a big ol' amplifier box. When I had the flowtech terminators on my truck, I hacked the tailpipes off because I hated the megaphones on it. It sounded good, but the bass off those tips caused every loose object in the truck to resonate. With just turndowns before the rear axle, it was much, much worse. So, I changed the mufflers (to aerochambers) and put the tails back on. Now, it sounds awesome and the resonation is gone. graemlins/thumbsup.gif