Go electric, no performance sound at all ... Yep like Mark said^^^, Most like some racket & raspy music coming out of the pipes!
At this point I really wonder what the OP's definition/tolerance of a drone consists of. It's subjective at best, but I can't imagine all those different combinations and six mufflers could not solve it for the satisfaction of the rest of the world's population!
For sure. My post isn't intended to be a dig on the OP, and he's certainly trying to solve the problem. I can't help but wonder if its just the nature of the beast- a V8 convertible is going to be loud.
Bingo!! He should put dual cats on it then some mufflers from a Silverado or Tahoe ( suitcase sized) then dual resonators.
I have a 1968 GS 400 convertible with side pipes. Definitely no drone, and it sounds like a four-cylinder on my side of the car. I think it goes like this, puh, puh, puh. I did drive around with the side pipes off, and just the chrome piece coming out from under the car by the front fender. That was pretty fun! Definitely didn’t have a drone though.
I think I may have eliminated about 90% of the drone. What’s left is not at an amplitude that resonates the whole car or dominates what you hear. Perhaps it’s really just the exhaust note at 1700-1800 rpm. What’s left of the exhaust sound is really quiet. The dynomax race bullet resonators up front, and then the 17749s, and way at the back… using the tees from the h-pipe kit, I ran two 31.5” lengths of pipe toward each other between the two tailpipes, along the rear of the tank inside the bumper. The tee outlets are now where tailpipe tips ought to be. So these quarter-wave resonators are at most 6” from the exhaust outlets. And they eliminated some really loud drone I had between 1450-1700 RPM. Now that I’ve experimented with this idea, I might see what adding or taking away and inch or so does. I put them together from a few lengths of pipe I had along with some short segments I can swap in or out. These pipes are currently capped off by… ready? the cut off bottoms of two 12oz aluminum cans. And this hodgepodge of things works. Even though the can bottoms are domed on the side meant to reflect the waves. The tailpipes are currently not connected to their hangers so it’s sitting a little lower than it will when complete. Once I’ve got them tuned the way I want them I’ll make a more permanent setup and some real caps (not cans) for the ends. If they’re too visible I’ll hit them with some hi-temp black paint. Exhaust doesn’t go into them, only sound. Because the ends are capped there’s no flow through it and no more room in it for gasses so the pressure keeps it out. They probably won’t get very hot. Because I’m sure you’ll ask, here is a picture!
I have a particular sensitivity to sound, and I have a bad case of tinnitus. I sleep with a sound app that makes “brown noise” which is lower and bassier than white or pink noise. I can’t tolerate the combo of the high pitched whine in my head and intermittent sounds from outside or the house settling. Up until I added the new quarter wave resonator pipes this evening, the car made an unnatural drone that did not go away regardless of how many sound attenuating things I threw at it. My other car has an aftermarket exhaust, which I expected and wanted to be louder than stock. But that car does not drone, though there are some infrequent times that it booms a little. If something I own buzzes, creaks, vibrates, and makes noises that are unpleasant I have to do something about it. Sounding like the ‘72 V8 powered car that it is would be fine. I think if you’d experienced this level of drone you’d agree it was unacceptable.
Almost went with cats, mostly because of the smell. It’d be nice to get where we’re going without smelling like exhaust. The EFI is running fairly clean and has reduced the smell a lot.
Hmmm...never seen or heard of anyone putting an H-pipe at the tailpipe of the system. The H-pipe is meant to go closer to the engine, generally just behind the trans mount. I don't really think it's going to do anything where you've got it installed. I'd be really surprised if it did.
The h-pipe kit is not being used as one. I did briefly try it as one, and if anything it made the drone worse. I’m using the tees in the kit for for another purpose described in another post. Two separate pipes than cancel the drone. And it works.
when i talked with the tech at walker about the drone in the dynomax mufflers he said to do what you did and add the race bullet mufflers to the system and that would cure the drone. i remember talking to someone or reading that using no larger than 2.25 pipes after the mufflers would also help drone. Chrysler muscle cars like the GTX and RT would come from the factory with 2.5 off the exhaust manifolds to the mufflers and then 2.25 tail pipes coming out the mufflers. looks like your on the right track now anyways.
Not yet, I wanted to try them without having to cut anything. I’m looking at putting them ahead of the mufflers but would need a pair of 90° elbows. I welded up some steel caps today. Next I’ll try to address the tailpipe that’s not far enough into the drivers side muffler, then I’ll see about situating the new pipes in a more permanent but less obvious way.
Your exasperating the issue by adding volume ( more pipes ) You’re creating an echo chamber. Go back to 2” head pipes and 1 7/8” tail pipes using the 17749 mufflers
Hi Mark, I can appreciate what you’re saying, but these tubes I added are doing something. And I don’t know that I want to buy a smaller diameter pipe set until I’ve tried everything (because I’m that stubborn). If they’re set to the right length the sound goes in and bounces off the inside of the end cap and then the sound is put back into the exhaust stream in reverse, cancelling the unwanted frequencies. So yes, an echo chamber of sorts. But on purpose with a specific goal. The length of the tube determines the wave that’s put back. Noise cancelling headphones are doing the same thing. They’re playing noise in a reverse phase of what the mics in the headphones pic up. There are plenty of cars with this tech, and plenty of cars that have as standard equipment one or more tubes on the exhaust or even the intake to tune out unpleasant noise. Yesterday I had the tubes set to a good length but today I changed it when I added the caps I welded and some drone came back. I’ll have to set them to 32.5”. I know, I’ve gone off the deep end, but there’s a method to my madness.
I had annoying drone issues with Flowmasters and the short case Super Turbo mufflers on my car. I switched to Dynomax VT mufflers and completely eliminated the problem. No drone at all. I'm not sure if they're still available.
I will say you have determination! Your obsessed, but I understand, I have gotten that way with car stuff too!
I understand the noise thing as after listening to printing equipment my whole life I get high pitch sounds in my ears, I mostly hear it when it is very quiet in the room. I always went to sleep with the TV on or the radio and never really noticed until the last 10 yrs or so. Recently I was shooting a shotgun and my earplug was not in tight enough now I have a fan running in my ear all the time. It has gotten better in the last 6 months but can still hear it. When you get this figured out you will have one hell of a recipe for a quiet exhaust. would have been interesting to have put this on a dyno and see if getting it real quiet would alter the Hp or TQ of the car.
