Sure there's quite a few here olde enough to remember the days that most vehicles just ran mufflers, and no resonators? My neighbor asked me that the other day,and I couldn't come up with an answer. Back in those days, most, if not all vehicles, didn't have cats either, don't know if that's related. I'm no bean counter, but seems like it would be cheaper to just run an appropriate sized muffler. Dumb question? Maybe.

 

Kinda wondered that myself. Actually, many vehicles didn't have resonators even 10-ish years ago? My 2005 Mustang had no resonators, just cats and mufflers, but the 2015 Mustang has a resonator.

Maybe it has something to do with factory mufflers now being more free-flowing than they used to be?

 

I think you are probably right. With factory setups flowing better, it is probably harder to control the noises. So, rather that install a giant muffler (heavy, large, and would just be removed by most owners), they have this 2-prong approach. Now they can give the sound you want in a package that will fit under the car.

I found this and it was an interesting read:
https://www.americanmuscle.com/musta...ifference.html

 

Good point there, could be. I very much remember on the higher performance Mopars, they had what they called a "reverse flow" muffler. I can't recall if they were packed or not, but I seem to remember the inlet would run close to the back of the casing them open up, and on the other side of the casing, the gas entered at the front, and out the back of the muffler to the tailpipes. I also remember how good those sounded after being burned in.
I guess you couldn't call that a straight flow by todays standards.

 

Thanks for the link. So, in the larger picture, maybe it is cheaper to run both, instead of the combination, resonated-muffler, or muffled-resonator of olde. Interesting.
I know traditionally we run the resonator in front of the muffler, wonder what the results would be if we did it the opposite?

 

Have you noticed how the Ram has resonators near the end of the exhaust? Has been that way for awhile now. Not sure about the Silverado but Chevy does that with the Tahoe too.

So I got to looking, talking about this stuff and thinking about my mention of the 2005 vs. 2015 Mustang. The 2005 Mustang came factory with a sort of "chambered" style axle back, and I heard that at the time it was one of the loudest factory exhausts in production. Yet these mufflers are known for not droning, even when the car is run with headers and no cats.

Looking at the 2015 factory mufflers they're similar in size, maybe even bigger, so it makes me wonder why they would need a separate resonator? Or maybe it's just further reductions in NVH.

 

I Guess I'm too brand loyal, LOL, never noticed that on the other trucks.
Odd you mention those "exhaust chambers". Back about '73, I had a '72 Comet GT, 302. I kinda knew a guy that had a Maverick, same thing, and we got to modding both of them. I used a pair of exhaust chambers for a Z28, went over the axle, and exited at both rear corners with cherry bombs that had down turned tailpipes. Like yourself, zero drone, but sounded great, turned a lot of heads.
Anyway, on my '12 150, I stuck a Roush on there, huge mistake, over the top noise, and mega drone. No matter what I stuck downstream of the Roush "muffler" I couldn't get the drone out of it. Looking at the Roush muffler, and the OEM resonator, they looked identical.
In that article, it mentioned the engineers figured this out, I guess that's what they get paid for.

 

From my reading, a lot of the drone is from the rear wall of the muffler being too far forward. (at least on pickup trucks) I've heard of people sliding a droning muffler back so that the muffler outlet is well behind the back of the cab and drone being greatly reduced...

IDK, but it would kinda make sense on the mustang as well to have the mufflers as far back as possible (behind axle)

 

The best sounding system I ever had was on a 460 converted F150. It had a typical old-school dual system (2.5") with a balance tube about 18" back from the collectors and 40" (yes, 40) Walker glass-packs. I think they were called blue bullets. It had a subdued thump at idle, undetectable at cruise and a nice roar when you'd hammer it down. Ah, the good old days! I AM one of the old fats previously referred to. ......

 

Well, I've also heard that having the mufflers at the rear of the car exacerbates drone. Example, Corvettes have the mufflers at the rear of the car and I've heard drone on them is terrible with aftermarket exhaust, and that's where Corsa got their start was with Corvette exhaust systems.

I know it's resonance but I still don't understand how it's affected by muffler placement or anything else. I put some chambered mufflers on my car a couple months ago, terrible resonance at low RPM's (under 2000 RPM). Put on this other axle back I have (Borla Touring), which has straight through, perforated core mufflers with a big case, and the low RPM resonance is practically gone.