FAQ: The Exhaust Thread

I''ll have is sorted out in a day or three. A friend claims to have some sound deadener sheeting that has no cement on it - that is, it's intended to be used by car builders with hitemp contact cement or some sort of mastic.

The thing is, what you want for sound deadening is a combination of eliminating the resonance in the panel and a sheet of lead between two layers of closed-cell foam. That failing, a sheet of plastic sound dampener betwen a couple layers of foam. The lead or plastic layer sucks up an awful lot of sound.

see http://www.jcwhitney.com/autoparts/Product/showCustom-0/Pr-p_Product.CATENTRY_ID:2010475/c-10101/Nty-1/p-2010475/Ntx-mode+matchallpartial/N-10101/tf-Browse/s-10101/Ntk-AllTextSearchGroup?Ntt=heat+sound --for the non-lead version.

Dynamat eliminates sound by turning it into heat. It is a tarry mastic loaded with little particles (not sure what, would not surprise me if it was fly ash or some such) with a layer of aluminum on top. Sound hits it and tries to move it, and generally fails. Point is it is not rubber and is not homogenous.

As for the where, I'm going to take a Saturday and remove (most of) the interior, put the dynamat (or whatever) over the center tunnel and on the floor. I'm going to thump the body pan with a sharpie to find our where it is drummy, and put the dynamat there. I'd like to get a roll of the Whitney stuff to put down as well.

Albertj

Thanks again.
Choices....choices...choices.

The choices are constrained by practical matters.

There are three things I have to do.

1) stop resonance. That goes by putting Dynamat on resonating panels. It does no good on panels that have patterns stamped in - they don't resonate. Panels with Dynamat will still pass sound.

2) stop sound transmission. This is hard - have to hear what's going on outside the car for safety reasons. But noise from the ground (tires, exhaust) is fair target for elimination. This requires padding. Closed cell foam with a 1/16" or so layer of lead on top would be ideal. Almost as good as lead is "mass loaded vinyl" which is the material in the middle of the JCWhitney 'sandwich' material. I already have foam and fiber padding, just need some of that vinyl stuff to go on top. This will suck up the sound that passes the Dynamat.

3) I need to take another look at the exhaust hangers and figure if I can make any changes there. I wonder if a different style of rubber hanger might communicate more or less vibration? This could be as simple as a trip to a Lexus or Volvo dealer...

The constraint is the whole 'system' has to be installable. that is the sound deadening can't be too thick and the replacement rubber hangers have to be a dimensional match. And there is probably a weight/gas mileage trade off.

For more on the sound barrier topic see http://www.sounddeadenershowdown.com/cgi-bin/index.cgi. I don't know where to look for exhaust hanger silencers - I think I am turning this into a snipe hunt...

Albertj

Do any of you happen to know if the factory exhaust off the DTS would fit our cars? I looked on monsterpartsonline.com andit looks almost identical except the tips. Look at the picture for the 2006 or 2007 DTS exhaust - they call it "muffler and pipe with engine code Y" about $651 from GM, all one piece ($110 freight!). GMPD has them too same price but $30 or $40 more freight.

any comments? any way to measure one (this is kind of asking a bit much BUT could work)?

Albertj

PS "Perfect Exhaust" content - friend of mine has some butyl/aluminum sheet I plan to use to get rid of resonances. Required I use contact cement or 3M spray to glue it on, I guess I need a wooden roller too - More later, I get a sample Wednesday.

I'm going full-bore with this car. Put the DS door boost gauge in. Looks great, btw. Pic below. At some point, I will be repainting this car professionally with brand new black paint (in about a month). There's a few other things I want to do but those will have to hold for the moment.

Looking to give this car a little snarl with exhaust. What's the cheapest route to go? I know my year Riv doesn't have a U-bend so I'm thinking of either hacking out the resonator or putting a more free-flowing muffler in there. Maybe GTP muffs?

Suggestions?

All you really need to do is change teh mufflers. GTP mufflers will work. Flowmasters (yuck) will work. I suggest Hooker "Maximum Flow" mufflers, actually. BUT Leave the resonator in.

Albertj

from a 3" DP can i stick with the stock converter or do i need to get a high flow cat because of the fact theyll be welded together?? i want to get a full 3" exhaust pretty soon suggestions would be appreciated..

esquire23 wrote:

from a 3" DP can i stick with the stock converter or do i need to get a high flow cat because of the fact theyll be welded together?? i want to get a full 3" exhaust pretty soon suggestions would be appreciated..

You can use the stock cat.

as i think about it should i go with 3" or 2.5" from cat back..would there be a dramatic sound difference between the two..i have 2.5 magnaflow mufflers and tips so what diameter should i go with after the Y

From reports I've heard, a 2.5" will be louder than stock, and 3" will be a lot louder than stock. The bigger diameter you go, the higher the drone and more raspy the exhaust sound.

Is there a need to go 3"? That's just huge unless you have an 11 sec car.

that makes alot of sense A DUB..idk i thought i read somewhere that supercharged cars benefit more from a 3" exhaust but i think ill go with the 2.5

You benefit from 3" if you've done some other mods to push more air into and through the engine. Until you're very heavily modded, the 3" won't give you much of anything, but you'll get plenty of noise.

More on engine air flow: https://rivperformance.editboard.com/series-ii-engine-transmission-f4/why-is-engine-air-flow-important-t194.htm

DEMonte1997 wrote:

I'm going full-bore with this car. Put the DS door boost gauge in. Looks great, btw. Pic below. At some point, I will be repainting this car professionally with brand new black paint (in about a month). There's a few other things I want to do but those will have to hold for the moment.

Looking to give this car a little snarl with exhaust. What's the cheapest route to go? I know my year Riv doesn't have a U-bend so I'm thinking of either hacking out the resonator or putting a more free-flowing muffler in there. Maybe GTP muffs?

Suggestions?

I might be convinced to sell you my custom exhaust when I have installed its replcement later this month (GM RPO is builidng it for a Park Avenue that they and I know I do not own... long story...) arrives. Look earlier on this thread, you'll find the YouTube videos. ATM I am planning to keep it as a "guy" decoration for the garage, and maybe reinstall it at some point. If interested PM me.

Albertj


Albertj

AA wrote:

From reports I've heard, a 2.5" will be louder than stock, and 3" will be a lot louder than stock. The bigger diameter you go, the higher the drone and more raspy the exhaust sound.

Is there a need to go 3"? That's just huge unless you have an 11 sec car.

I went to 2 1/4 from the Y back to a pair of custom made SS mufflers. It snarls nice, but I doubt going bigger buys anything.

Albertj

L67 wrote:

esquire23 wrote:

from a 3" DP can i stick with the stock converter or do i need to get a high flow cat because of the fact theyll be welded together?? i want to get a full 3" exhaust pretty soon suggestions would be appreciated..

You can use the stock cat.

Yes, stick with the stock cat. I used to work for the company that made the substrates for that cat - it's a fine technology and as GM has installed it, is very free-flowing. If you do change consider getting the Walker cat, same technology for the substrate and as well, enough platinum inteh converter's washcoat to actually work as OE intended.

Albertj

albertj wrote:

turtleman wrote:

AA wrote:

I would suspect the attenuation in sound above 3000 RPM means your engine's output pulses have raised above the exhaust system's resonant frequency range. It doesn't mean it's flowing any more or less exhaust. Based on your exhaust system diameter vs. length as a whole (including mufflers), the resonant frequency is the exact point at which you hear the drone. The reason our stock system has no drone is simple - its point of resonance is below the frequency range that we can hear.

I was thinking about this and it confused me here. How does that whole resonance-pipe concept not go out the window once you put in something totally irregular like a muffler.

So far I've only heard one non-original muffler that cancels virtually all detectable resonance and thats the walker muffler I'm using now that's designed for the 4.3L v6 motor. That muffler was the only thing on the exhaust that was really changed from the previous highly-resonant set-up using the dynomax superturbo.

just comments...

1) the whole resonance pipe concept stays in (does not go out window) with a muffler because from a physics point of view the muffler modifies the length and diameter of the pipe BUT does not make it suddenly be not a pipe.

2) I am thinking some of this 'drone' comes from how Rob hung the muffler at the stock points - changed the stock rubber hangers. I will take a closer look one day when I have time on my hands. The other thing is I think I can improve things with a layer of dynama, somethign I'd been meaning to do.

3) I also wonder if I have a wheel bearing that's dying, and so some of the noise has nothing to do with exhaust.

Albertj

I put eDead (a dynamat clone) in the trunk, 1 layer, and on the floor pan under the back seat and the back edge fo teh carpet (also just under the back seat). I made a deadening pad out of some mass loaded vinyl and a flameretardant carpet pad, and fitted that under the back seat. I added a layer of the flameretard pad to the auto board panel behind the back seat. Bottom line is the combination took care of the noise problem, although i'm still replacing the exhaust (again) at some point (I will miss it). For someone who does less highway driving than I do, this exhaust would be the cat's pajamas. For me, the exhaust is fun until after 5 hours or so straight... does sound sweet though...

Albertj

albertj wrote:

DEMonte1997 wrote:

I'm going full-bore with this car. Put the DS door boost gauge in. Looks great, btw. Pic below. At some point, I will be repainting this car professionally with brand new black paint (in about a month). There's a few other things I want to do but those will have to hold for the moment.

Looking to give this car a little snarl with exhaust. What's the cheapest route to go? I know my year Riv doesn't have a U-bend so I'm thinking of either hacking out the resonator or putting a more free-flowing muffler in there. Maybe GTP muffs?

Suggestions?

I might be convinced to sell you my custom exhaust when I have installed its replcement later this month (GM RPO is builidng it for a Park Avenue that they and I know I do not own... long story...) arrives. Look earlier on this thread, you'll find the YouTube videos. ATM I am planning to keep it as a "guy" decoration for the garage, and maybe reinstall it at some point. If interested PM me.

Albertj


Albertj

I'm probably going to just go with GTP mufflers. Was supposed to have them installed today but looks like that will have to wait until Weds. I don't really want much performance from this car so the only other thing I might add is a 3.6" press-on pulley. Thanks for the offer though. Your exhaust sounds really good.

Tentatively, this is my next exhaust plan. These are really not just parts thrown together. I definitely went under and measured shit and the plan evolved a bit since its conception. I plan to do some experimenting with this at the very least to see about how loud it will be so I know if I'm way off base with the muffler setup or not. Obviously that drawing is not to scale and a lot of things look unrealistic but it serves as a parts map anyways.

Will update with more later

i think the spare tire well is in your way.

Albertj

Just a friendly reminder to the folks who haven't yet messed with their exhaust systems, but are thinking about it. As Aaron noted earlier, you don't need major reconstruction unless you've done some heavy modding to your motor. My comment is that more sound from a Buick V6 is usually not better sound...

I've heard Slant 6 Mopars with headers that sounded very V8-like. On the other hand, Buick may have cleaned up the vibrations of this engine with the split-pin crank and the balance shaft, but when it comes to the exhaust note, you just can't get around a 120-degree firing order bent into a 90-degree V. Even our Turbo Regal had a quiet exhaust system.

I've listened to a dozen different modded 3800's, and they all seem to have the same unpleasant resonance around 2,000-2,500 RPM, and they still sound almost "foreign" the rest of the time.

Yep, my stock exhaust system (cat back) will probably stay on until it needs replacing. The exhaust note of a 90º V6 is definitely not one of its strong points.

I think the unequal length primaries of the FWD variants make it worse too. Here's a Holden L67 video i found where the exhaust sounds pretty good...I wonder how he did it. (Revving at the end)