FAQ: The Exhaust Thread

well at the moment, thats not even on my agenda. the exhaust is fully functional as is and it's not too loud for me. The hissing sound annoys me more than the tone coming out the back.
Right now i'm working on getting ready for an XP cam but I think i'm gonna buy a bike first actually

yeah the bike deals start at this time of the year

The resonators you describe as using reflection also are packed with sound deadening material (like fiberglass). They use reflection and absorption.

A lot of resonators are basically just a glasspack too (the ones I am putting on my riviera are like this... dynomax p/n 24225/24226). They use absorption an reflection.
You're right when you say that a true Helmoltz resonators don't use absorption. I'm just saying I don't know of any "mufflers" that are JUST a Helmholtz resonator.

I'm going to cut open the stock resonator from the riviera to see what is inside it.

never said mufflers, I said resonators. There is a difference. Look it up if you want to.

The resonators you speak of are designed not to impede flow and deliver more sound than a normal one, but quieter than not having one at all. Hence the combined reflection and absorption you speak of. Most true resonators are only there to tune out some sound frequencies, make the exhaust sound cleaner.

An easy way to tell the difference between a glasspack and a true Helmholtz Resonator is to "ping" one with your finger. A glasspack will make a dull thud, and a true Resonator will make a clear "ping!" sound.

But while youre cutting stuff open try cutting open a flowmaster deltaflow "muffler" and see if you see anything in the chambers.

But like I typed earlier, I'm not here to argue. I didn't want to prove anyone wrong, I just wanted to give input. Let's just leave it at that.

I don't mind being wrong, as I very well may be in this case. There is certainly nothing wrong with discussing something. That's why I like forums like this one. We're on the same page. We're both saying basically the same thing. I think I just misinterpreted what you meant by a "true" Helmholtz resonator. A lot of silencers (both resonators and mufflers) use the principle of Helmholtz resonance, but I thought that by "true". you meant a simple cavity that uses nothing other than that, sort of like the one we have on the stock intake pipe.

Even if that IS what you meant, just because I haven't seen any silencers that use only Helmholtz resonance doesn't mean they don't exist.

I went to check out one of the resonators I have lying around. It is a dynomax 24225. I flicked it with my finger and it does "ping". I don't want to cut it open (for obvious reasons), but this would mean that its insulation is found sandwiched between two layers of its outer shell, like most other "true" resonators as you call them. It uses mainly Helmholtz resonance to tune out a specific frequency, but that little added insulation allows its body to absorb some of the pulses, but not in the way a glasspack would. <- so there would be the answer to turtleman's question.

On a related note, the magnaflow mufflers that a lot of people use on regalgs.org and clubgp are not "true" resonators. They are circular mufflers. They work pretty well thought. Length and diameter will make a substantial difference between them.

turtleman: what do you mean by hissing?

About the flowmasters: I know they don't have any packing in them.


People either love flowmasters or they hate them. I am not a fan. They get their signature sound by bottling up the exhaust and slamming the exhaust pulses back into each other. While they certainly flow more than our OEM pieces of crap, they aren't the best choice on a performance application.

the hissing comes from the front-ish of the car and increases with throttle/load. You hear it whenever you drive by something like a close wall or a car. But when that happens, it's pretty loud and unattractive. I looked at the welds and stuff of the pipe and there are no leaks there. I'm guessing it's the downpipe flex which kind of makes me irritated because I tried to get the best downpipe i could to prevent that. It sounds like a malfunctioning turbo or something, just not nice

There is very minimal clearance to wrap it

My headers made the same noise until I wrapped the flex-braided area.

Same here. Wrapping it didn't make it go away completely but it made a big difference.

I have 3" into 2.5" with Magnaflows (no resonator) and I am happy with the exhaust note. It is raspy and pops a little if you rev it iout of gear but with the engine in gear and under load it sounds much more mello.

I would like to compile information on exhaust for everyones reference

Would everyone please submit information about exhaust components, pictures of installs, sound clips, other relavent threads just anything at all here.

The goal of the thread is to understand the Riviera exhaust strengths, its flaws and when it becomes a bottle neck (if ever). And when is a good time to upgrade. Also to show diffrent exhaust steups and info for others to use as reference.

Here's a link to a photo of our stock exhaust system:

https://rivperformance.editboard.com/series-ii-engine-transmission-f4/what-s-my-exhaust-system-look-like-t70.htm

My current exhaust consists of headers (3" down pipe included), deleted cat converter; entirely stock from there back. It is still very quiet, and have recorded 248 WHP (300 HP) on the dyno using a 3.4" pulley at 80ºF.

My current exhaust consists of pacesetter headers, 3" downpipe, Deleted cat converter , and stock exhaust . I would say the sound went up 5% at most.

It should be noted that Rivieras do not have a U-Bend like the GS and GTP.

I know there are not supposed to be any dumb questions and this group has enough class not to blow this question off so I'll just solicit the opinion of my fellow Riviera friends:

what would happen if...I modified my exhaust system by eliminating both the resonator and cat and replacing both mufflers with just one located where the old resonator was previously located, I would then have a nice gentle "Y" pipe and two short tailpipes with some nice tips...and what i would hope to be a nice free flow and rumble.

I've only owned one 6 cylinder in the past (66Rambler American) and that's all it had as stock from the factory, it ended up with a cherry bomb but that was a different time...

I don't see why your idea wouldn't work, but it would be loud, and unless the muffler was large enough, more restrictive than a pair of smaller mufflers.

I've heard that mufflers do the best job farther away from the engine, so moving it closer to the hotter, fast-moving flow might have some negative effects. Probably just louder, though.

that 5% increase in sound is about what i see with the 3" DP and cat delete, so i'm guessing headers dont make it much loouder at all.
i do know the riv w/out a resonator sounds nasty (and not in a good way) but thats an opinion.
i'd like to know how restrictive the T pipe is vs. a Y in its place. worth the effort/money?

I have slp knock-off headers with a 3" magnaflow where the resonator used to be. It turns out that most commecially available y-pipes have too narrow an angle between the Y to make a decent dual exhaust. Also, you can't find a T pipe, unless you buy a complete H pipe kit (which means that the ID = OD)

Therefore I went a single 3" all the way to the where the T used to be, followed by 2 90 degree mandrel bends and a 3" to 2.5" reducer into a single 2.5" hooker maxflow with a turndown tip.

I haven't fired it up yet with the new exhaust, but photos are comming to show the rediculously small stock stuff.

Also, straight headers is loooooud.

Quote :

that 5% increase in sound is about what i see with the 3" DP and cat delete so i'm guessing headers dont make it much loouder at all.

Your 5% and someone else's 5% are going to be totally different without actually measuring. I have a sound level meter that I can use to get in-car measurements. I can send to meter out to whomever wants to do the same test.

Headers may not make the exhaust note much louder, but being thinner/lighter steel, they let engine noise escape that would otherwise be absorbed by a heavy, cast iron manifold. I would say at least a 10% if not a 20% perceived increase at WOT, just from adding headers. And much of that change is "felt" through vibration rather than heard by ear.

One item to note would be that if you don't have a bad cat, upgrading to a high flow will not net you much gain at all.

I'm very interested in noise with aftermarket setups. I will probably be replacing the back half of my exhaust this summer and want to increase flow as much as I can without making a loud car.

Right now I'm thinking I'd get a zzp 3" whisper resonator, then after the Y have 2 2" regular old heavy duty mufflers.

Here's another thought to consider about exhaust flow:
the big old Buick V8 455 cid does nicely with dual 2.5" pipes. It's 7.4 l displacement. Compare that to a 3.8 l running at 2 atmospheres of boost (200 KPa) and you are talking about the almost the same CFM of airflow (give or take a little), pushing through 1 3" pipe after the front and rear header come together. I haven't done any math to back this up, but it sure seems like a 3800 flowing twice as much air would be about as much as a 455. (I bring up this reference mainly because we have been playing with 455s for many more years than 3800s)

I have SLP headers running into a Magnaflow High-flow cat leading back to two Ravin mufflers with Ractive chrome tips. It's honestly not much louder in the cabin than when i first bought it. There's a little drone, but nothing that will really get on your nerves. It sounds a hell of a lot better than my friends GTP.

nothincame2mind wrote:

I have SLP headers running into a Magnaflow High-flow cat leading back to two Ravin mufflers with Ractive chrome tips. It's honestly not much louder in the cabin than when i first bought it. There's a little drone, but nothing that will really get on your nerves. It sounds a hell of a lot better than my friends GTP.

Edit: just looked at sig.


I love where this thread is going keep it up guys.

In my personal experience, the resonator primarily takes care of the 1800 to 2200rpm drone. The Riv has a quiet cabin compared to the W bodies so it can be tolerable. Of course this is while still running a real cat, which I have been told acts as a resonator of sorts. YMMV


I know nothing about 455s, but I do know that NA cars rely on some amount of back preassure for exhaust scavenging. This is not the case for an engine with forced induction. So comparing displacement and pipe diameters, might not be a good comparison. O' course I could be wrong.

I noticed very little drone, if any, when adding headers and deleting cat, leaving the rest in place.

what set up should i get to get the most drone, i love drone,i got it from driving the titan with straight pipes(long tubes, no cats no res no mufflers)

so i want drone with my car drone is good rasp isnt