FAQ: Mufflers?

This shows exactly why it's so difficult to build a custom free-flowing exhaust that's also whisper quiet. It also shows that it's quite possible to do with research, design and proper execution (there is a belief that you MUST have noise to make power - this is not so). As albertj indicated, the chambers are tuned. This has to do with the relationships between the length & widtch of each tube, and the volumes of air each chamber. It's a type of bandpass helmholtz resonator, and it must be specifically tuned to match the resonant frequency of the system, or the drone frequency.

I believe the OEMs are tuned specifically for our cars, whereas the aftermarket super turbo style mufflers are tuned for a range of probable frequency. That explains why you gain sound level (drone) with the aftermarkets, and it explains why one model may sound quieter than another on a specific car. While flow is increased, so is the sound, but it's not a result of more flow, imo. It's the result of the tuning being off - because it's made for an average target, and that target is likely a V-8.

Here's a really good idea that lets you tune the muffler on the car while running: link

AA wrote:

This shows exactly why it's so difficult to build a custom free-flowing exhaust that's also whisper quiet. It also shows that it's quite possible to do with research, design and proper execution (there is a belief that you MUST have noise to make power - this is not so). As albertj indicated, the chambers are tuned. This has to do with the relationships between the length & diameter of each tube, and the volumes of air each chamber. It's a type of bandpass Helmholtz resonator, and it must be specifically tuned to match the resonant frequency of the system, or the drone frequency.

I believe the OEMs are tuned specifically for our cars, whereas the aftermarket super turbo style mufflers are tuned for a range of probable frequency. That explains why you gain sound level (drone) with the aftermarkets, and it explains why one model may sound quieter than another on a specific car. While flow is increased, so is the sound, but it's not a result of more flow, imo. It's the result of the tuning being off - because it's made for an average target, and that target is likely a V-8.

Here's a really good idea that lets you tune the muffler on the car while running: link

The 'cool' thing for me is it looks like speaker enclosure tuning, which I know how to do - but also involves fluid flow (exhaust gas) tuning which I do not really know how to do. However, looking at the cutaways, I see what's going on. The Corsa exhaust, for instance, uses a more complex Helmholtz adding cost (albeit modest) and weight (which might not have been a bad thing except for the fuel economy implications). Again, thank you Robo.

A side note - this also explains to me why my retrofitted OE PA exhaust has bigger mufflers than the OE Riv does, and why it does not seem to have that "flat spot" around 2000 - 2500 RPM like my original Riv mufflers had. The PA internals are probably a similar setup to the Riv but tuned to pass all the gas and then some without making any sound worth a darn. The necking inside the muffler inlet on the Riv exhaust is a modest restriction but they probably *had* to do it to get the sound right and for just about everything but racing it would not matter. On the PA exhaust they used very heavy end plates on the mufflers and put ribs in those plates, I suspect to get rid of (via conversion to heat) that last little bit of sound from the inlet pipes.

I can also see that on a less expensive car, cost would dominate performance and hence a "Tuner" who does not care about drone and noise within legal limits can likely get more whizz and boom out of certain 4-banger cars with almost any exhaust upgrade.

Albertj

AA wrote:

This shows exactly why it's so difficult to build a custom free-flowing exhaust that's also whisper quiet. It also shows that it's quite possible to do with research, design and proper execution (there is a belief that you MUST have noise to make power - this is not so).

I can't tell you how true this is. The biggest challenge we face with the 455 in my brother's Buick is keeping it quiet. We tried several different mufflers, unfortunately gave up before we found a satisfactory sound level. It's very very hard to keep quiet when you have 455 cubes, a big cam, long headers, running crisp and a little lumpy... but what we've done is not too shabby.

It's annoying how many people prefer the noise.

Thanks for the pics robo, very interesting.

Welcome!I kept the right side muff.Really all I have to do is weld on 3" Inlet/outlet tubes,enlarge the stock perforations,and ill have a stainless steel/OEM modded muff! for free.

robotennis61 wrote:

Welcome!I kept the right side muff.Really all I have to do is weld on 3" Inlet/outlet tubes,enlarge the stock perforations,and ill have a stainless steel/OEM modded muff! for free.

if you enlarge the stock perforation you maybe might want to wrap the tubes in stainless wool (won't pack) or a mix of rock wool and stainless (wrap tubes in stainless so the rock wool does not blow out although it will matt down somewhat)

just sayin...

Albertj

I might do that,but with the Thrush super turbo being only $35,I might just get one.And I just remembered,my welder wont do stainless steel.I have a basic wire feed lincoln. Oh well...

Anyone have experience with Magnaflows on a Series I Riv? Just curious...I'm thinking about upgrading my exhaust.

This is what I'm installing on my Riv. Of course, I'm more concerned with appearance rather than performance.

ghpcnm wrote:

This is what I'm installing on my Riv. Of course, I'm more concerned with appearance rather than performance.

If you're connecting those mufflers to an otherwise factory exhaust, a 2" or 2 1/4" inlet would be easier to deal with. Those pipes entering the OEM mufflers are pretty tiny.

Yeah, I'm doing new pipes from the cat back

ghpcnm wrote:

This is what I'm installing on my Riv. Of course, I'm more concerned with appearance rather than performance.

That should look very nice, similar to the stock tips. Can't wait to see them on the car!

okay, ordered two magaflow 11225's and two magnaflow chrome tips

2 1/4 inlet and outlet. will have y-pipe redone to make whole system 2 1/4. Not huge, but bigger than the 2" which runs from the y-pipe

taking her to meineke for a/c work,muffler and suspension work


then she's just about 100%

Natesriv wrote:

okay, ordered two magaflow 11225's and two magnaflow chrome tips

2 1/4 inlet and outlet. will have y-pipe redone to make whole system 2 1/4. Not huge, but bigger than the 2" which runs from the y-pipe

taking her to meineke for a/c work,muffler and suspension work


then she's just about 100%

making the pipes bigger is likely to give you a certain drone.

just from the y-pipe to mufflers... 1/4 inch bigger than what's there now...

was thiking the main pipe was 3"...but it's 2 1/4... so the system should be all the same size..

these are "performance" mufflers... bought them to add a little noise...not too much...not too little.

we'll see!

Natesriv wrote:

just from the y-pipe to mufflers... 1/4 inch bigger than what's there now...

was thiking the main pipe was 3"...but it's 2 1/4... so the system should be all the same size..

these are "performance" mufflers... bought them to add a little noise...not too much...not too little.

we'll see!

"noise" yeah but drone is going to make you angry.... I mean it's your car not mine so knock yourself out... I think to get the sound you want you're at the stock pipe sizes but putting on a pair of Magnaflows or Hooker Maximum Flows. I'd suggest the Hookers.

hard to believe ijust read every page. ok soooo. 3 inch down pipe to cat, then what to get the best performance yet quietest sound. will be mofifying the car later. or just get the downpipe and plog and keep stock mufflers for now.. I tell ya off topic that ilve the way these cars pull silently lol

well, I wil keep the OEM mufflers! But I don't know about a drone. I'm not going from a small pipe to a larger,or from a larger to a smaller. It's all 2.25"

Won't know until they're on next week.

BTW...I'm in KCMO

106 next three days...it's F'ing HOT!!!!!

has anyone tried a muffler similar to the Firebirds and camaros exhaust? the on n 2 out of a single muffler

My opinion is that mufflers don't matter on these cars unless you want to be able to hear the 3800 V-6 sound. The OEM muffs aren't that restrictive, and have been retained in builds up to the 300-400 HP range.

If you want the quietest sound, keep it stock cat-back. The performance is already there from the factory, and our exhaust is a quality stainless system that will last. You won't gain much replacing mufflers until you are at an advanced modding stage (heads, cam, etc.)

Okay had the two magnaflow 11225's installed.

They are 2.25" mufflers with the same inlet/outlet pattern we use on our Rivs'.

They sound great. Not too loud, no highway drone and when they do make noise, it's at the rear and a mid bass sound...it doesn't reverberate thoughout the cabin.

I love it!!!!, had some chrome tips welded on as well..

Meineke did it for me, with the a/c fix and the alignment, (I bought the mufflers first)..it was a very low cost mod!

At the y-pipe...all OEM from here to engine...but all new from y-pipe back. Guy did a great welding job!


with the new chrome tip


stainless stell Magnaflows...


Chrome tips I ordered too...better than I thought!




Overall, not 100% symmetrical, but damned close....


I'm totally happy with the results!!!...did NOT set off the car alarm you hear..

wow! those sound really good

They look good too!

I have those same tips!

thanks! I think that's the last mod I wanted to do to the Riv...so she's all set for another few years!