HELP! The interior resonance is killing me

[boonie]

i just installed two magnaflow mufflers on my 94 vette pt# 15623 it,s beautiful. but! the interior resonance is KILLING me, what can i do about it? would installing two resonators solve the problem? but won,t that hurt performance by creating more exhaust restrictions? what can i do?
boonie

 

[Ken]

You oughta hear mine! I'm workin' on it though; if the stuff I used works out, I'll let y'all know.

 

[afree]

I have the same problem with my 88 Coupe. It has pretty unrestircted flow (no cats) so it's pretty loud. I run Dynomax mufflers (not top of the line but I have been told on more than one occasion it sounds pretty darn good.)
I've been thinking about a crossover at the front or maybe even an X pipe.
Let us know what you guys do to solve the problem since I am pretty sure there are a few of us with the same problem looking for answers.

 

[grapeknutz]

I have dyno max super turbos and a Dr gas X crossover in place of the resonator and I don't have any resonace. Hope that helps.

 

[afree]

grapeknutz,
Excellent news...could you provide me with a little more info? Where did you get it? Easy to install? Welding required? etc..etc...
Thanks

 

[grapeknutz]

grapeknutz,
Excellent news...could you provide me with a little more info? Where did you get it? Easy to install? Welding required? etc..etc...
Thanks

The X cross over was bought from Dr gas $180.00 and had the local muffler shop install it. The stock resonator was cut out and the x cross over was welded in place. I think this quelled the resonace that others keep reporting.

 

[afree]

Thanks for the info...will investigate to see if they have one applicable to my aftermarket system.
Thanks again

 

[Ken]

My "x" is a Spin Tech:

...with Flowmaster 40 series mufflers.

_ken

 

[rrubel]

My god! A garage messier than mine!
[RICHR]

 

[Ken]

That's actually Will's shop Rich. Everybody has their own method of dealing with their work space. :eyerole

Mine's as clean as a whistle. As a matter-of-fact, Nolan, my maintenance man may he rest in peace, said my garage was cleaner than his apartment. But then, I do have what you call an obsessive/compulsive personality. Or is that disorder? :L

 

[rrubel]

It's only a disorder if it becomes a handicap .

I do know where everything is in my garage; if I were to clean it, I'd never find stuff again.

The exhaust is a nice piece of work, but are there no cats on it? The floor end connects straight to the headers, right?
[RICHR]

 

[Hotred94]

I have a 94 with a Flowmaster 40 and no resonator. The resonation was killing me too, but it sounded so beautiful on the outside of the car that I couldn't bring my self to quiet it down any. So instead of attacking the source of the noise, I consentrated on absorbing/muffling the interior noise. I put on four or five layers of insulation all over the middle and rear of the car. This worked out pretty well. Now I have decent noise levels inside with killer sound outside. When I get my new muffler tips, I will extend them further out the back to reduce the noise even more.

 

[Magmotor]

What type of insulation did you use?

 

[Ken]

... no cats on it?

Shhhssshhh!!!!

The floor end connects straight to the headers, right?

Correct.

For everyone's information, I am thinking of getting some Thermo-Tec "clamp-on" exhaust pipe wrap to install on my exhaust from the collectors to the mufflers. (It's too late to wrap the headers because they're on the car already, and I'll be damned if I'm gonna pull them again just to wrap 'em - I've had just about enough of having to do things two, three, or even four times while doing this project phase of mine.) :L

When I do that modification, I'll be sure to let y'all know how it turns out. It makes sense in the it would trap the heat in the pipes, as well as route the noise through the pipes and out the rear without causing a lot of interior resonance.

_ken

 

[rrubel]

Shhhssshhh!!!!

No worries, mate. Just thought it looked awfully LONG for a catback exhaust... or those are 1/2" pipes!

Be interested to hear about the insulation; I get more resonance than I'd like with my setup as well, but it's liveable.

[RICHR]

 

[regalniz]

what is the size of m 94's exhaust pipes? im gonna get one of those x pipes.

 

[Ken]

what is the size of m 94's exhaust pipes?

If it's stock, it's got:

• ENGINE, EXHAUST SYSTEM:
• Type: Dual
• Muffler number and type: Two, tri-flow (straight-thru for LT-5), aluminized stainless steel
• Muffler weight: 62.98 lbs (LT1), 62.5 lbs (LT5)
• Resonator number and type: One, cross-flow
• Exhaust pipe branch o.d. & wall thickness: 2.75" x .054"
• Exhaust pipe material: Aluminumized stainless steel
• Intermediate pipe o.d. & wall thickness: 2.75" x .04"
• Intermediate pipe material: Aluminumized stainless steel
• Tailpipe o.d. & wall thickness: Single wide wall 0.54" (LT1) , 2.75" x .05" (LT5)
• Tailpipe material: Aluminumized stainless steel

_ken

 

[regalniz]

wow. that was a wealth of info. one question though. if the resonator is "cross flow" why put on an x pipe? wouldnt it be louder? i have borlas and headers and the interior is loud.

 

[Ken]

You have two camps in regards the "x" pipe and its value in added exhaust flow and its supposed horsepower increases. Some say its worth it while others deny any benefit from its installation. I happen to fall into the former catagory; I believe the crossover helps exhaust flow by its scavenging effect, that is, one bank will help pull the exhaust from the other bank.

I started putting that stuff I have from Gulfstream (it's used to isolate, and partially insulate, the cabin area) into my interior and I believe it is going to be a great sound deadener. I only have a couple of pieces in so far, but I can tell simply by pounding on the areas where I have it installed that it removes a lot of the "drumming" you usually associate with floor panels. Once I get the carpeting back over it, I should have a noticeable difference in interior resonation.

_ken

 

[regalniz]

hey ken congrats on your 10500 post. your x pipe info is invaluable but does it reduce resonance?