FAQ: Mufflers?

I've tried a sound recording from inside with the widows down but had too much wind noise. I will try with windows up at idle, 70 mph cruise, and uphill making boost

You might want to get that cat out of your back dash first. The clawing into the leather to keep from splattering might ruin it.

What size is the stock exhuast pipe before and after the mufflers?

I have a vid of my stock exhaust too if anyone wants to compare

shes just so HOT!!!

kevin, why does your "stock" exhaust have angled tips? or am i missing something?

1wickedninja wrote:

1wickedninja wrote:

What size is the stock exhuast pipe before and after the mufflers?

1 7/8"

thanks man!

Okay, a couple of questions.... First, what are the headers for, are they for the Rivi or for a Pontiac, and second, does anyone know of some mufflers that will sound good on the Rivi...I don't want it to sound like a bumble bee, just a lil tone to it. Thanks

well the headers fit the l67, (series 2 supercharged) and good mufflers are borla mini turbos, and my personal favorites flowmasters

kingfam95 wrote:

Okay, a couple of questions.... First, what are the headers for, are they for the Rivi or for a Pontiac, and second, does anyone know of some mufflers that will sound good on the Rivi...I don't want it to sound like a bumble bee, just a lil tone to it. Thanks

General consensus in the 3800 community would be that they sound best with borla or magnaflows , with a lot of people also liking dynomax.

Thanks... If running the Flows do/would you use the 40 series or the 60 series which are designed for 4/6 cylinders. Also is it ok to decat it, will it still have enough back pressure.....Thanks again

you should go with the 40, and the decat doesn't really affect anything other than dead weight imo. and if i'm wrong im sure someone else will chime in

kingfam95 wrote:

, does anyone know of some mufflers that will sound good on the Rivi...I don't want it to sound like a bumble bee, just a lil tone to it.

Flowmasters are not the masters of flow.

Backpressure is widely misunderstood. You don't need backpressure. If you're that concerned by it, you won't want to run flowmasters. Unless you LOVE the sound of flowmasters (and that's fine), there is no reason to run them.

yes you can ditch the cat, but your car will throw a SES light. You need to tune for it or get an 02 simulator.

Jason wrote:

Backpressure is widely misunderstood. You don't need backpressure. If you're that concerned by it, you won't want to run flowmasters. Unless you LOVE the sound of flowmasters (and that's fine), there is no reason to run them.

yes you can ditch the cat, but your car will throw a SES light. You need to tune for it or get an 02 simulator.

Just to back this up - if you think you need backpressure look at this:


This engine clearly makes it's power just fine with no backpressure. Backpressure is misunderstood, and it does have purpose. If you get rid of your cat and mufflers, you will need a retune but it won't hurt anything besides your ears... This is a forced induction engine, with off-the-line forced air input. Backpressure is not nearly as significant to our engines.

Jason,
What mufflers are you using.?
I'm paralyzed trying to decide. I want to enable flow but don't want a lot of noise.
I'll sacrifice some HP for a mellow tone.
I'll be installing headers and a 3" high flow cat, plan on leaving the stock resonator and would like to change mufflers. Just don't know what to buy. Have read everything I can possibly find regarding mufflers for these engines and have received many differing views.

Quote :

Have read everything I can possibly find regarding mufflers for these engines and have received many differing views.

Rick, if you want to read even more, here's a collection of good exhaust articles. Everyone has a slightly different point of view. I tend to side with the idea that louder means better flow, but at what cost? You can give up a little bit of power in order to have a lower noise level, and still have a relatively fast car. It's my firm opinion that the differences in muffler design make a bigger impact to noise levels than they do flow and power output, as long as the correct size is used for the application.

https://rivperformance.editboard.com/series-ii-engine-transmission-f4/great-exhaust-articles-t1680.htm#67527

i run 2.5 magnaflows with a deleted resanator its not that loud and they sound nice! if u pick up the magnaflow and hold it right u can see right threw them. much better flow than flowmaster. i had flowmaster 40s on my 86 monte and i swaped them for magnaflows. if u ask me they have better flow and a nicer sound.

i will try 2 make a sound clip this weekend if i have time or remember lol

Jason wrote:

Flowmasters are not the masters of flow.

Are they less restrictive than stock mufflers, yet produce a mellow tone.??

I've been thinking about ways to quiet my exhaust down (even though I really don't want to) so I can shake the attention of the police. It's the only thing that gives me away.

I was looking at a pair of 2.5" Thrush turbos as a cheap and certainly quieter alternative to my current Dynomax superturbos. After looking at one of those exhaust articles that basically said the superturbos I have no are about as best flowing as you can garentee yourself without knowing anything else and that the Thrush turbos are horribly restrictive. Damn so that plan is shot to hell. I will not give up that much flow.

Secondly, would it be quieter to run one muffler from my 3" catless system or two (theory being less pressure on each muffler so less noise with two). Right now, I have a jiggy riggy Y split that's really one pipe with a hole cut in it and another pipe welded to it. If I decide for sure to run two mufflers, I'm going to first replace that section with a true Y. I think that alone will make a difference as I can clearly tell a very noticable difference in pressure between the left and right exhaust exits.

I don't really feel that I need to maintain dual exhaust - would be fine with single - but I want the setup that will give me flow and quietness. Again, I am very happy with how it sounds now so I'm really not trying to manipulate it any more than simply quieting it down enough so I feel comfortable driving the car late at night with cops on the street.

PS I also have a 3" piped dynomax race bullet resonator about where the cat was so If you think that plays into anything that would affect my best setup (dual or single muffler / alternate muffler)

this very thread wrote:

The formula for required exhaust flow is: horsepower times 2.2.
So
if your car makes 400 hp, you will need a total of 880 cfm muffler
capacity for an unrestrictive exhaust system. So for dual exhaust, you
would need mufflers that flow 440 cfm.

I probably should have put the above in bold. If you want an unrestrictive exhaust, you should strive to have flow approximately equal to hp * 2.2. Some people express the hp figure as the amount of loss-free hp the exhaust can sustain. You don't need 1000 cfm for a stock riviera.
Let's ASSume that your car makes 300 hp. Your muffler combo should flow 660 CFM for your exhaust not to be "holding you back." You can run one 660 cfm muffler or two 330 cfm mufflers. Anything more, and you won't gain anything. Anything less, and your exhaust will be costing you hp. Arguably not much if you're very close, but it's still a couple hp that are "easy" to find. My educated guess on how much the stock riviera's exhaust costs the car would be 7-15 hp (depending on mod level).

Rickw wrote:

Jason,
What mufflers are you using.?
I'm paralyzed trying to decide. I want to enable flow but don't want a lot of noise.
I'll sacrifice some HP for a mellow tone.
I'll be installing headers and a 3" high flow cat, plan on leaving the stock resonator and would like to change mufflers. Just don't know what to buy.

To answer your question Rick, My exhaust consists of ss autochrome type headesr, a 3" magnaflow round muffler that I use as a resonator of sorts, 3" all the way to the back where it tapers down to one 2.5" hooker max flow muffler. It's quiet at idle but screams at WOT. Practically no drone. I should have gone with the longest "resonator" I could find but I bought a used one for cheap.

As to which mufflers you should run, I can only say run the ones whose sound YOU will enjoy. With most modern aftermarket mufflers on a "low" hp car, it mostly boils down to sound (other factors would be price and corrosion resistance). My overall recommendation for your exhaust setup would be:
Don't use the stock resonator. If you're taking the time to add headers and are concerned with your exhaust enough to buy mufflers, why would you leave a muffler whose diameter is no greater than 2" (which is preceded and followed by 2.25" crush bent pipe) ?
I'm going to ASSume that you want to keep your system as a "dual" exhaust and that you're concerned with corrosion. I recommend stepping up to a 2.5" or 3" resonator. A lot of people have had great success with the magnaflow round mufflers. Go with the longest one you can afford. For your mufflers, based on what you've said above, I would recommend a pair of dynomax super turbos in 2 1/4" (p/n 17748...the longer the case, the quieter the muffler). This will be more than enough for a car with respectable mods. Both the magnaflows and super turbos are guaranteed for life. If rust isn't an issue for you, you may want to consider summit turbo mufflers for the rear. They are similar to the super turbos at a fraction of the cost. While installing my setup, I temporarily put on a pair of dynomax super turbo 17749's that I had lying around. I actually really liked the sound and tone, but they are offset/offset and it was not really practical to use them.

edit

Quote :

Are they less restrictive than stock mufflers, yet produce a mellow tone.??

yes, practically anything flows better than a 1 7/8" oem muffler. I think the smallest flowmaster you could get would be 2". I still think the flow results above have a typo wrt the 2.25" flowmaster. There's no way a 2.25" muffler is going to flow 90 cfm more that a 3" muffler of the same "series". I think 2x 2.25 flowmasters would be adequate for a stockish riv.
No they don't produce a mellow tone, especially not on the 3800. I personally don't like the sound, but you shouldn't take my word for it. Try to find a clip of a gtp or regal GS with flowmasters and see if YOU like the sound. If you do, go for them. A sound you enjoy will certainly be worth the 1-2 hp it might cost you (probably none if you were to use 2x 2.5"). I'm not saying you should avoid them at all costs, just that there are better options out there for your money.

the simple of it: I believe I found a muffler for people running full 3" systems without a cat or resonator and with headers and everything if you want it all to be quiet and DRONE FREE!

Ok so I was at work today and I was just glancing at the muffler section since we got converted to an O'Reilly store now and I decided to look in some more. I came to a large Sound FX muffler by Walker on the shelf. Part number 18223. It's a big boy - 7"x9"x20" body with an OAL of 24" Pipe is offset on both ends 3" on one side and 2.5" on the other side. It basically looks just like a turbo design from what I can tell by looking inside it. I had already decided that I needed to do something with my exhaust because it was a duece too loud to drive around at night (especially after parties and stuff when there is 1 cop for every 2 cars out) so I said "why the f not?" It costed something like $36 for the muffler and I got some other stuff for installation. Retail price puts it right with a dynomax superturbo and on that note, its construction quality and design are comparable.

I cut both my 2.5" superturbos off and clamped this onto the side that it seemed to fit more easily in. I don't think the way I have it is quite permanent but It can be, funtionally. I'll take some pictures and post them tomorrow night, hopefully.

I drove the car for a few minutes with the muffler on. It's quiet but not factory quiet. Much to my amazement, all of the 1550-2100rpm drone is totally gone. It's freaking amazing! It still lets out the nice idle sound this motor has too. I haven't gone WOT with it yet because when I drove it today, it was raining and dark out but I will play a little bit tomorrow, assuming it doesn't rain or snow all day.

I have a short video of it in a closed garage. I'll make an outside video maybe tomorrow.

Interesting. More please.