But for most folks using packed vs chambered mufflers, resonance is an uncommon issue. I won't suggest using resonators as a band aid just yet. Though they would probably take care of the symptom, it would be nice to find the root cause of the problem. Devon
I agree dump the Flowmasters. I went from 3" to 2.5" with Dynamax mufflers on my 53 and got rid of the drone. It is still 3" until after the cross over. The 70 is 2.5" all the way with Dynamax but I won't know how it sounds until I get the tailpipes from TA and get them on the car. Bob H.
I understand that a lot of people dislike Flowmasters, totally ok and everyone is entitled to what kind of sound they prefer. However my drone issue was there (before) I installed the Flowmasters. And was there while I was even using two different sets of Dynomax mufflers (straight through design and a super turbo with matting) and even a standard generic muffler.
Did everyone just bypass Davy's first post without reading it? Come on guys, he's already past the difference in mufflers at this point. Get your collective brains on and think of what could cause a 2000 rpm resonance after all he's been through. I'm having trouble thinking that the short headers could be a factor, but you guys need to think about the whole thing, too. Devon
Ok Devon here my 2cents... 1. Small cam and gears that like to cruise highway rpms at 2k +or- 2. Now maybe it is in his non mandrel bent pipes 3. Or the length of pipe after the mufflers 4. The fact that the open muffler is up under the car and not out back. Idk I've always had some drone unless I had a reso.
Thanks Devon. And thanks to everyone who has been gracious with their time. I would hate to give up any performance but I think I am at the point of where I would rather the car sounded really well without the drone. Meaning this summer after I pull the car out from hibernation I think I am going to cut off the tail pipes again. Then somehow direct some shorter pipes out to the side before the axle to get rid of the fumes. Hopefully the (seat of the pants) power loss I felt was nothing but a figment of my imagination.
Any chance the exhaust system is over restrained? Were any hangers added (even deleted for that matter) that weren't originally there? On my GS I ran 2.5" exhaust from the exhaust manifolds back into an X with DynoMax 17749 long case mufflers into 24215 Bullets behind the axle. The car was quiet, no drone, no loss in performance. With that combination my GS ran 11.7x's and as I said, very quiet. Seat of the pants can be very misleading. You could add a pressure gauge before the muffler and check your pressure at WOT with any and all exhaust combinations. If you do this, you'll need a section of hard line from the exhaust otherwise vacuum line may melt. You can use 1/8 NPT fitting in the pipe connected to hard line, then hose clamp vacuum hose to the gauge. The gauge doesn't need to read very high. Are you running a package tray with factory type sound deadener? Another thing that will affect exhaust NVH is temperature of the exhaust isolators, when fully warm the system will have better NVH vs. cold. Open element air cleaners may add to your condition. Try swapping back to a stock one to see what changes, you may have more than one issue confounding the situation.
My son had a 5.3L in Tahoe. He installed a Corsa muffler that had no drone UNTIL he also installed a K&N cone air filter. It was almost not a drone, but the intake definitely added to the audible mix at particular RPMs at highway speeds.
I have shortys on my 53 with no drone. They are the same shortys from TA that fit the Rivvys. Metal to metal hangers could cause a droning sound. Bob H.
Perhaps there is a resonant frequency in the chassis and body of his vehicle the the exhaust excites. Perhaps flowmasters cause a lot of drone because they amplify a spectrum of sound waves that are in tune with most vehicles chassis/body system. If that were the case, it would be likely that unless a drastically different exhaust setup was used, the drone or resonant frequency would still exist because it is excited by the tail pipe section and flowmasters (reference lack of drone without tailpipes). He might have had issues with other mufflers just because of the way his specific vehicle reacts to the spectrum of sound waves emitted by his exhaust system. I would reckon that each vehicle would be slightly different due to variances in manufacturing, body work, etc. I would say that minimizing the transfer of exhaust vibration would likely help a problem like that. Make sure that all the exhaust hangers are the rubber isolated mount type and maybe you could even try using dynomat in the trunk and back seat floor areas. Other than that, finding a muffler that least amplifies that spectrum sound waves is going to be your solution. I run long tube headers, a 3.5" to 3" x-pipe, and 3" mandrel bent pipes all the way back with Spintech mufflers. They sound great and do not have what I would consider 'drone' while driving. They are loud, but there is no resonant frequency drone that makes me want to puke like you describe. I know what you are talking about though as I had a flowmaster on my old truck and it made me want to crap my pants on the highway.
its not the exhaust system its the buick motor nothing drones like they do when i was in highschool my buddy (my car now) wasnt allowed in the carport with his car cause it rattled pictures off the wall everytime this was with manifolds and single 2" stock exhaust but if you held it at abouth 2000 it droned more than anything ive ever heard now that i put headers and full dual 3" and 40 flowmasters out the back it drones waaay less lots louder but the wall shaking drone is basically gone dont listen to what they say their exhaust did to an old corvette or whatever unless it has a buick in it our motors have a sound of their own
for smooth and quite," stock rocks" other than that you have to cancel the resonance wave in the pipe behind the muffler or it will not go away.
You might try Hogans mandrel bent tailpipes, since it only happens with tailpipes. Just a guess like everyone else. The for sure cure is just run open headers :idea2:
