Resonance

[Alfonso Gomez]

My 87 Coupe was in dire need of new mufflers and rear Y-pipe. The passenger's side muffler had a big hole in it and the Y-pipe had numerous holes in it. It sounded like a muffler-less Harley. BUT NO RESONANCE!!!!!!!

I ordered from Mid America Motorworks a Dynomax
Y-pipe with balance tube and a set of Dynomax Performance Mufflers (Part Number 603-406). It was easy to install and they sound good. BUT.......the resonance is killing me. From 1600 to about 2200 rpm it is unbearable.

My car is practically stock with only a few mods: KN filter, cut lid, coolant bypass, Hypertech Thermomaster chip, TB airfoil, no cats, 3:07 rear end. It is an automatic, by the way.

What can be done to reduce this nasty resonance?

 

[SPANISHVETTS]

Try extending the tail pipes about 2¨past the back bumper. How far back is the balance tube?

 

[sothpaw]

CAts

Put some Cats on there. Cats reduce the sound as much as mufflers.

 

[Vettelt193]

Many times performance mufflers make more resonance inside the car than just straight pipe. The problem is the sound bounces around inside the muffler, and instead of going out the tail pipe, it tends to bounce up and down (up into the interior and down into the ground).

You can either dump the mufflers for straight pipe or a different set of mufflers... or you can pad the interior with sound deadening material.

I have used a roll of stuff from home depot before, very cheap, and fairly effective. not as good as Dynamat, but good for the price. It was a silver foil looking roll of stuff, good for heat and sound deadening.

On my '93, I layered the whole interior with it. My right leg used to get hot (and still does on my '96 because i haven't done it yet) from heat from the tranny and engine. after I put the stuff under the carpet, it was much better. (although, I never really had a problem with resonance unless I was (or am) cruising in a gear too high for the speed... ie, 6th gear at 40 MPH while accelerating)

 

[vetteboy86]

I happen to like it, I guess my age is the main reason. I usually have ACDC so loud I cant think anyways. Maybe when I get older and have to turn the tunes down I will not like the resonance. But until then I love it.


Good Luck
Craig

 

[EttevroC]

Please forgive my ignorance but what does this resonance sound like?

I own a 1989 convertible and I’ve read that resonance is a big problem with the convertible. I would like to purchase some throaty deep sounding exhausts but am worried that I will end up finding out I just blew buegue bucks on a system and find out that I hate this resonance thing you all speak of.

Does anyone have a suggestion of what brand and model exhaust would full fill my criteria but will not produce this resonance problem?

Thank!

 

[drags1998]

You gotta promise not to laugh at this idea!!!! !! A friend of mine has an 87 coupe, bought the same system as you did, Noise was also KILLING him!!!!! He took some pink fiberglass insulation & stuffed the INSIDE tailpipe on each muffler and it cured his problem!!!!!! And, he claims NO loss of performance!!! JUST an idea!!!!!

 

[jgmotto]

I ran Dynomax mufflers with their Y-pipe for a few years, too, and had the same problem with resonance. I tried everything, including packing insulation in the body cavities around the mufflers. I finally replaced them with a Flowmaster Force II kit (mufflers and Y-pipe) from Summit. Problem solved. Now it sounds great, gives good performance and absolutely no resonance. They claim that they stagger the sound waves to cancel out instead of multiplying them. I don't know but it seems to work.

 

[NT Vettman]

I just installed a Flowmaster Force II exhaust system this past week end. Sound great! Yes they have a small resonace at about 40 MPH under light load, but other wise not that loud at highway speeds. thay have nice low roar when accelerating. The polished round stainless tips look great to, and installation was a snap. Beside these are performance exhausts if you want quiet, drive your dad's Buick

 

[WhalePirot]

Second set of Flowmasters, too; different motor. What IS resonance???

BTW, there was quite a long thread about mufflers a while back Try a search for more poop. It was started by a Chicagoland green '93 (I think) owner.

Actually, the first pair is sitting, available, in SoCal, attached to the stock rear Y-pipe.

 

[froggy47]

Corsa.

 

[Vettefan87]

Maybe it is just because I am young, but I love the resonance my Monza Mufflers put out. Usually I've got the radio up to loud cranking ACDC or Ozzy to hear it . But for now I love it


Justin

 

[ShaneL]

I just took off my cats and mufflers and experienced a very big increase in resonance. This noise sounds like you have a window down in an SUV (sort of a booming). I used Dynamat and Extremeliner as well as the factory sound deading mesh. I can pull back the carpet and show you all a picture of the install if you are interested.

Let me know,

-Shane

 

[Vettelt193]

Maybe it is just because I am young, but I love the resonance my Monza Mufflers put out. Usually I've got the radio up to loud cranking ACDC or Ozzy to hear it . But for now I love it


Justin

I had monzas on my '87 vert, and it didn't have resonance... The sound we are talking about isn't sound coming out of the tips of the tail pipes (ie, the good sound ), rather, a sound that is booming, to the point where it feels almost pressurized in your head. I love loud exhaust, but do not like resonance.

My Dad's 98 pace car sounds fantastic... that is, until you hit certain speeds with the top up... it is horrible at 73-75MPH and at 90 mph. At 90, you can't hear the radio over the resonance because it is so bad! It is actually less noisy with the top down. What does he do? either goes 77, or goes slower than 73.... or the best option, just drop the top.

 

[wilezcoyote]

I just put the TPIS cat-back Flowmaster setup on mine. The system has no resonance and nice deep sound. I actually wish it were a bit louder.

The only thing I'm not crazy about is the muffler tips stick out about 2" past the bumper. I called and asked them about it and they told me that that's what they had to do to fix the resonance problem.

 

[Rogue]

Corsa.

I would dearly love to get the Corsa's but the company seems to believe that us L98 owners don't exist!

They only make the exhaust for the LT1's and ZR1's.

 

[Green LT1]

I had great luck with my Magnaflows. Great sound, polished stainless steel, very good price. They make a cat back for L-98s, and mufflers only for LT1's. I had a pretty long thread late last year regarding my search for mufflers. Good luck!

 

[EttevroC]

Thanks Shane and others for the definition of resonance; I now know what that sounds like now. I own a PT Cruiser and if I open just one window and leave the other 3 up, I get a sound that can almost be described as a low pounding noise.:duh



Shane, I would very much like to see the pictures you took of installing sound insulation. What it hard to remove the carpet and get it back into place?

 

[ShaneL]

To remove all of the carpeting in the rear area I had to remove the trim peices around the hood weatherstriping, the speaker grills, speaker assemblies (I put it in there also), Hard top hanger covers and the brackets themselves. and you have to remove the latch on the passenger side storage compartment. I also removed the storage door assembly and put sound proofing in the passenger's side but I left the driver's side alone. All of the carpet peices should lift out as well as the factory sound proofing.

I will be back in a minute to post pics.

-Shane

 

[WhalePirot]

Coyote- My Flows got louder with age, so you might get UR wish.

I wonder if I can get the 4 tips chromed. The Green LT1 was the thread I referred to earlier.