Fixed My Exhaust Drone

[Some Car Guy]

So if you don’t get the length just right, do you just end up moving the drone around?

 

[Charlie Brown]

So if you don’t get the length just right, do you just end up moving the drone around?

No. You are trying to reduce drone from 100% to 0% at the same rpm.

 

[Moparfever65]

Just when I thought I'd seen everything...

 

[Krooser]

I dislike the sound of those chambered mufflers. They don't anything like a muscle car when new.

Give me a good set of glass packs any day. Cheap, effective and throaty...not tinny.

The State Patrol even stopped me a few times to tell me he could hear my glass packs! Nice of him...

 

[Bird 426]

So they don't stop all drone, just at a certain rpm, say 2,500rpm at 55mph?

 

[khryslerkid]

No thank you.

 

[Charlie Brown]

So they don't stop all drone, just at a certain rpm, say 2,500rpm at 55mph?

It can cancel all drone if you get the right combo. In my 62, I've been able to get 100% elimination, my 64 is at about 90% - that's why I haven't finished the final permanent weld. I need to drive the 64 a bit more to fine tune it. I will get it to 100%.

 

[33 IMP]

So they don't stop all drone, just at a certain rpm, say 2,500rpm at 55mph?

They will stop all drone, if the tuned length is correct.
There is math involved if you are comfortable with that, or you can make it adjustable till you get the right length. Like Charlie Brown is doing.

 

[Bird 426]

Okay, thank you!

 

[j-c-c-62]

I'm thinking the dead pipe gets just as hot as the regular exhaust does?

plus, they're directly next to the regular pipes, so they'll get pretty warm. Never IR gun temp measured them though.

"warm " is rather subjective. Without any internal flow at speed and with normal ambient exterior air flow, they are IMO likely never to get close to the heat of the regular exhaust.

What's the thinking on the pre or post muffler location for the 1/4 wave traps? I see both locations shown here.

Why not plumb the 1/4 wave trap with the idea of having proper airflow, pre muffler, locate electric cut outs at the needed distance, and plumb the exit of the cutouts where needed, and kill two birds at once?
Nobody cares about drone with an open cutout.

 

[j-c-c-62]

They will stop all drone, if the tuned length is correct.
There is math involved if you are comfortable with that, or you can make it adjustable till you get the right length. Like Charlie Brown is doing.

That is if your drone is a single frequency and only at one frequency (not a given). This solution here is tuned to 1/4 wave, which means it will also cancel other frequencies but maybe not as much, or wanted to or not, in 1/2? octaves. Nothing is 100% canceled, but enough to likely be masked by all the other frequencies at play.
FWIW, 120 Hz to 240Hz is one octave, 240 to 480hz, another, 480 to 960hz another and so on.

 

[Charlie Brown]

"warm " is rather subjective. Without any internal flow at speed and with normal ambient exterior air flow, they are IMO likely never to get close to the heat of the regular exhaust.

What's the thinking on the pre or post muffler location for the 1/4 wave traps? I see both locations shown here.

Why not plumb the 1/4 wave trap with the idea of having proper airflow, pre muffler, locate electric cut outs at the needed distance, and plumb the exit of the cutouts where needed, and kill two birds at once?
Nobody cares about drone with an open cutout.

It does not matter where the 1/4 wave resonators are placed in the system - before or after mufflers - makes no difference. The added pipe length may differ though. Location is mostly a function of where it fits the best.

 

[68 Sport Satellite]

And just to clarify - on my car I'm not running chambered mufflers. I run Dynamax Ultraflow Welded, which are a straight through design. Had some pretty annoying drone. I love a tough muscular rumble, but drone at speed for a long drive can get pretty annoying.