Tired of being heard from 2 counties over...
 

I currently have long tube 1.75" hookers, a custom 3" Y-Pipe and the rest is from an SLP cat back with their 3" in/ dual 2.5" out "straight through" muffler.

The muffler is really just two glass packs in one package. It consists of an internal "Y" and two straight through, perforated tubes. The perforations are just holes, no "bent lips" like some other glass packs have. It has been on the car for 20 years.

You can hear my car idling from two blocks away. My Wife tells me that she can clearly hear me accelerating onto the freeway from over 1 mile away. I would say that it is currently about 80% as loud as open pipes.

I'm wondering what the state of the art in mufflers is these days. I would like to find something that will not hurt my performance TOO much, but will allow mild acceleration without attracting the attention of everyone within 1/2 mile. We are talking about pumping 600HP through one muffler.

Ideally a drop in replacement with 3" inlet and dual 2.5" outlets.

Any suggestions?

Thanks

Re: Tired of being heard from 2 counties over...
 

Therein lies the rub.
A general rule of thumb is that an exhaust system has to flow about 2.2 CFM per HP produced before performance starts to become limited. (Yes, yes. I know. Joe Hotrod has a 2000 HP street car running a Flowmaster 30 series....).
At 600 HP, you're looking for a 1200 CFM unit. As far as my research goes, that's the territory of the race "bullets" like Borla or Dynomax. And with that comes volume.
I've considered splitting the exhaust just after the axle and running two muffler in the stock location. The choices are greatly improved and if selected appropriately, I would think that there is enough room. It would mean a couple of round mufflers as opposed to the traditional oval shaped case.
Have you considered a couple of cutouts just back of the headers?
In my case, while I'm nowhere near 600 HP, I've added a cutout at the turn just before the muffler. There is a verifiable difference in strip performance with it open vs closed.


https://cimg7.ibsrv.net/gimg/www.thi...a557fe2ee6.jpg

Re: Tired of being heard from 2 counties over...
 

I've dropped my Y-Pipe while on a dyno and and gained 10HP/lost 10 Torque on back to back runs with my existing system. So I don't think that it is really much of a restriction now.

Way back "in the day" I had an exhaust with two "turbo" mufflers in the factory location. So that can be done.

I've also considered replacing the SLP with a pair of longer bullets/glass packs, or replacing the tail pipes with bullets/glass packs. With the straight through design, I don't think that it will hurt performance any.

Re: Tired of being heard from 2 counties over...
 

Curious. Did you any collector length to the header? Because if not, I can GUARANTEE that the torque would suffer a great deal. The typical LT header collector of about 6" is at a point where the "tune" gets in the way of efficiency. (According to PipeMax).
That said, this isn't the point of your thread so I won't belabour the point.
Certainly the idea of a pair of mufflers would help resolve the flow vs output vs loudness issue.
And as you demonstrated with the dropped exhaust, it's a combination of the entire exhausts flow potential including the muffler and the pipes preceding it that are what counts. You just don't want the muffler to be a cork to make things worse.
Here are a few old files I dug up when I was researching this topic.



https://cimg6.ibsrv.net/gimg/www.thi...9ab92c345f.jpg

https://cimg7.ibsrv.net/gimg/www.thi...ab6704ffc8.png

https://cimg8.ibsrv.net/gimg/www.thi...46d9f45987.gif

Re: Tired of being heard from 2 counties over...
 

Put a "Loud valve" on that and you can have the best of both worlds at will.


Opens only when you get on it :
https://loudvalves.com/collections/v...nt=32909320076

Re: Tired of being heard from 2 counties over...
 

Something I've thought about. The real issue here is that my 2 into 1 and a single 3" over the axle exhaust presents it's own restriction. With a new engine in the works, something a little closer to the OP's 600 HP (but really just shy of 500), I think at least a 3 1/2" is more appropriate or perhaps Hookers duals at 2 1/2".

Re: Tired of being heard from 2 counties over...
 

Thanks SkinnyZ - this is some good data. :)

I'm not a big fan of cutouts. I've gotten away with crazy loud all these years, I don't really want to choke it down to the point that I need cutouts to get my performance back.

I have a couple of old (new in box) Dynomax 24214 bullets.
I don't think they use that part number anymore, the closest I could find is these:

https://www.summitracing.com/parts/wlk-24219/overview/

I originally got them (with a stainless "Y") thinking that I could duplicate the SLP muffler, running two in parallel, just bigger outlets and a little longer...or maybe put a "U" and run both in series.

I may still try the series idea.

BTW, did I mention that I have a 4000 RPM stall? I know, I'm fighting a loosing battle...

Re: Tired of being heard from 2 counties over...
 

I've been looking at some the mufflers in SkinnyZ's data and the Dynomax Ultra Flow (1000 CFM, Dynomax claims 2000 CFM) seem to have similar construction to what I have now, but it would take two of those (17218) to match the one SLP I have now.

I say the SLP is worth two of those because it has a similar straight through design, but internally it has two 2.5" passages. Going by that, I'm beginning to think that I may just have one of the best flowing (and loudest) mufflers around.

Re: Tired of being heard from 2 counties over...
 

I also have the SLP 3" exhaust with that same muffler you are using.
I will be fabricating a "catalytic muffler" for mine (a muffler in a cat converter case).
Have you considered installing a "race" muffler in the converter's stock location?

Re: Tired of being heard from 2 counties over...
 

My exhaust is routed differently, only one side is there. The other side doesn't have room for much other than the oval pipe that passes under the transmission cross member..

Re: Tired of being heard from 2 counties over...
 

The 121 mph trap speed in your profile suggests low 500-ish HP at the crank. That is a stout car though! Your car is movin'. :)

Your muffler is really old and the sound absorbing packing gets less effective over time. I think you'll be pretty happy with direct fit replacement. If you want to change dimensions then the larger the muffler housing the quieter it will be.

Re: Tired of being heard from 2 counties over...
 

Oh, I forgot to say that catalytic converters are fantastic mufflers. Things get loud without them.

And you're right that perforations that bend down into exhaust stream results in quieter muffler. I know Stainless Works is designed that way. Not sure about Borla but they have some top notch stuff.

Re: Tired of being heard from 2 counties over...
 

Ya that's prevailing thought but I think that is aimed at race cars that are concerned about every last HP. I'm no expert but I think in a street car application with full exhaust that the HP losses are fairly small with moderately undersized catback exhaust. Every now and then you see somebody pick up a crazy amount of power with an exhaust change but I suspect the gains have more to do with improving cylinder scavaging where engine makes peak toque than it has to do with just flow numbers of catback pipe.

Again, I don't actually know and I'm just throwing around some ideas. What I do know is that I spent $200 on dyno time to find out my "undersized" 3.5" exhaust didn't cost me even 1.0 horsepower. In fact, the best torque curve was with full exhaust. I would have preferred to keep that money.

Re: Tired of being heard from 2 counties over...
 

Is this close(by dimensions)what you have now? http://www.dynomax.com/ultra-flo-sta...ed-offset.html
I have dynomax at Camaro,and it is not crazy loud at idle.

Re: Tired of being heard from 2 counties over...
 

Those numbers were from about 5 years ago. With pretty bad wheel spin, 100lb(rim+tire) steel wheels (17x9/ 0.25" thick steel) and a worse tune. It is noticeably faster now...but still has wheel spin issues if I don't run drag slicks.

Ya, the SLP was always "loud" but may not have always been "crazy loud". Replacing it with another muffler with new fiberglass probably would make it quieter...but I would prefer a solution that doesn't include replacing the muffler every few years.

Re: Tired of being heard from 2 counties over...
 

I agree.

In an ideal world every part of the exhaust would be tuned to be a perfect match for your displacement, cam, RPM, intake, gear ratios, etc, etc, etc.
In the world I live in, trying not to smash the exhaust flat on a speed bump is a more pressing consideration.

BTW, as I mentioned earlier I had a similar dyno experience. Dropping my Y-Pipe and running open headers (besides melting some wires) didn't make much of a difference. Yes, (as someone said) adding collectors would have helped, but my exhaust goes to oval pipe with a few inches of the headers anyway, so it didn't lose much collector length. With the oval pipe, the lowest hanging part of the exhaust is the 4 into 1 part of the header.

Re: Tired of being heard from 2 counties over...
 

In actuality, the CFM vs HP is directed at street cars where those interested are trying to reproduce open headers performance with a suitably muffled system.
And by open headers I mean headers that are tuned length.

The picture below is a big inch small block (Corvette I think) where the system as installed was within a few percent of open header output.


https://cimg2.ibsrv.net/gimg/www.thi...b7b28edc3e.jpg

Re: Tired of being heard from 2 counties over...
 

This post is very telling.
Yes, it has everything to do exhaust scavenging!
Pumping into a pressurized exhaust is hardly efficient and power will be reduced as a result. So there is some relevance here. A single muffler 3rd gen exhaust will hardly allow back pressures of a reasonable level.
That's all I'm saying here.
That you dropped your exhaust on the dyno demonstrated practically nothing other than your dyno technician's lack of knowledge (or unwillingness perhaps) and informing you that some arbitrary length introduced onto the end of the collector could worsen results. Your test was virtually worthless. Unfortunately, it was $200.
Now, if someone had calculated and experimented with suitable extensions and tuned accordingly, then did a comparison with your muffled system, I can guarantee that the amount gained might be of interest. 10%? 15%. But what's 50 HP really?
And just so this is put into context, I'm not advocating that anyone try and replicate the system posted earlier. It's just an example of what's possible. For the rest of us, the biggest pipes with the least restriction (of the correct length even with tail pipes) is the way to go. As Qwk demonstrated, output is still very much on the healthy side even if there is room for improvement. (Just wait until the new engine arrives!)

Re: Tired of being heard from 2 counties over...
 

Now, all of that said, I'll apologize for muddying up the thread with being off-topic. I'm somewhat passionate about the topic and have witnessed countless examples of science being dismissed because of some poorly executed testing procedures.
As for esc's desire, to replace his muffler, all I have on that is a list of potential candidates as posted earlier. I also ask if the Hooker BlackHeart full duals have been considered?

Re: Tired of being heard from 2 counties over...
 

I'm not familiar with this. Any details?

Re: Tired of being heard from 2 counties over...
 

https://www.holley.com/products/exha.../70501426-RHKR

This is one of 4 available I believe.

https://www.thirdgen.org/forums/ltx-...roduce-lt.html

Re: Tired of being heard from 2 counties over...
 

Jump in at post #571. The 4th gen dual exhaust is reportedly a direct fit other than the typical headers to mid-point adaptation.

https://www.thirdgen.org/forums/exha...xhaust-12.html

Re: Tired of being heard from 2 counties over...
 

I assume you're referring to my car. I think you're over estimating the gap by an enormous amount in my case (open headers vs. 3.5" full exhaust). As for fueling, I have Holley HP EFI with wide-band O2 sensor so the tune automatically adjusted to hit target A/F ratio.

I wasn't on the dyno to design an exhaust system and the shop just did what I asked. I was there to simply find out if my muffler and/or 3.5" pipe was hurting me badly (as so many people on the internet claimed). Turns out my exhaust is fine.

When I dropped the muffler (and just the muffler) the car made 25 lb-ft less torque across the board out to 5300 rpm where it finally gained about 5 RWHP out to 6500 rpm where the curves merged again (end of my power band). A drag racer might take the 5 Hp because they are concentrating on power band between gear shifts, but in my street car I'll take the broad +25 lb-ft any day over a measly 5 HP in the last 1000 rpm. By removing the muffler, the exhaust system gained air flow potential as measured on a flow bench, but for the most part the engine performed better with the muffler. Go figure.... 'compressible flow' is a strange animal.

I don't plan on going up in exhaust size with my next engine either. I've talked to a few engine builders that have seen a lot of F-body's and they think my losses will be single digit HP compared to using dual 3" exhaust. I have $2500 sunk in my exhaust system, it packages well, it sounds AWESOME, and I'm not abandoning it for single digit gains.

Re: Tired of being heard from 2 counties over...
 

Regarding the OP's high output engine with 3" single exhaust.... ya, I do think the engine is being choked with significant potential left on the table. 3.5" exhaust would uncork it pretty well. 4" exhaust is so damn loud but it's a lot easier than 3" duals. Duals are no joy to package and needs a proper crossover or it's not worth doing.

I wouldn't bother with the Blackheart if it is 2.5" duals. A single 3.5" is about equivalent and much easier to package. Heck, it might be entirely equivalent considering the 2.5" duals have a lot more boundary layer surface area to deal with.

Re: Tired of being heard from 2 counties over...
 

It looks like the Black Heart system is for an LS swap. Is that right?

I've had a (smaller) dual 2.25" system before, with both pipes routed on the passenger side and it was a pain. The systems that have both pipes in the center, generally have ground clearance issues...maybe with a custom/purpose built cross member they could fit better.

I'm pretty happy with my current Y-Pipe setup. A 2.5" pipe has a 4.9" cross section. My current 4.5" x 1.5" oval has a roughly 6" cross section, and on the driver side, passes under the cross member with very good ground clearance (never lower than the header 4-1). The passenger side uses the stock routing. The "Y" is just before the rear axle. My single 3" going over the axle is a little bit of a bottle neck, but not terrible. I'm inclined to think that my money ($1,000) would be better spent elsewhere.

It does look like a very nice setup, just not for me, not now. After I blow up this motor, I'll probably do an LS swap. Then the equation may be different.

But back to the original topic. It looks like the only mufflers with enough flow will be the same basic straight through design. With that in mind, the Dynomax bullets that have been sitting on my shelf for who knows how many years, may still be my best choice.

Re: Tired of being heard from 2 counties over...
 

The first picture is what I originally had in mind when I bought these parts.

Leave the over-axle pipe in place.
Remove muffler and tailpipes.
Install 1 into 2 (3" in Dual 3" out) and two 3" bullets.

The problem with that is that the bullets are the same length as the existing muffler. With the external "Y" it will be too long to get the tail pipes into position. (Remember the SLP muffler has an internal "Y" and two shorter 2.5" passages.

I could replace the existing muffler with one of these bullets and a single 3" tail pipe. It would have new packing and MIGHT be quieter. It would be a pretty easy mod, I would just have to get one end of the bullet expanded to fit over the existing over-axle 3" pipe.

Maybe I should use one where the existing muffler is and use the other AS a tail pipe. :)


The second picture is just to give you a view of the straight through nature of these.

But somehow, I don't think that this will make any real difference in how loud it is.

https://cimg3.ibsrv.net/gimg/www.thi...336b0bd95f.jpg

https://cimg5.ibsrv.net/gimg/www.thi...bbd9ffd714.jpg

Re: Tired of being heard from 2 counties over...
 

I have been giving this more through and putting something else with fiberglass packing back on doesn't seem like a long term solution to me.

I thought Borla used stainless steel wool packing, but they don't.

Does anyone know of a straight through muffler that does use SS packing, not fiberglass?

Re: Tired of being heard from 2 counties over...
 

Here you go, these have SS wool packed in them.

https://portermufflers.com/porter-mufflers/

Re: Tired of being heard from 2 counties over...
 

Came across this:

https://www.magnaflow.com/automotive...ound/products/

Not certain if there's any packing at all.

Re: Tired of being heard from 2 counties over...
 

The Magnaflow says " acoustical fiber fill" which I guess is fiberglass.

Re: Tired of being heard from 2 counties over...
 

Those look nice.

I've been reading up on muffler construction and it turns out that even SS filling will eventually wear out. It seems that it flexes with each pressure pulse and eventually metal fatigue will cause pieces to break off and fly out. It takes longer with SS than FG, but it still happens.

I wonder if the solution is a rebuildable muffler?
There are muffler rebuild filler kits available on ebay and amazon.

Either rebuildable, or maybe easily swapped out inexpensive throw aways?

Re: Tired of being heard from 2 counties over...
 

Didn't see that anywhere. Only "100% stainless steel and lap-joint welded for solid construction and rugged reliability even in the most extreme conditions. They feature a free-flowing, straight-through perforated stainless steel core."

EDIT: Found the description. Yep. Acoustical fibre fill....
So much for all stainless construction.

Re: Tired of being heard from 2 counties over...
 

Remember the Supertrapp muffler that uses the discs? Would that help your situation?


http://supertrapp.com/images/product...lite-5in-1.jpg

Re: Tired of being heard from 2 counties over...
 

Not sure. Don't those make the exhaust have to do a 90 degree turn to get out between the disks? More disks=louder? Sort of like a partial "cut out"?

What I do remember about Supertrapp, is that they were really loud. But the guy I knew with one, just left the disks completely off, so it basically was a cut out.

Re: Tired of being heard from 2 counties over...
 

I have never tried Supertrapp, or even heard one. But there is no packing material to blow out and the sound level is adjustable by the number of discs you use. And you can also get them in stainless steel.


I wonder what would happen at an emissions test? Where do you insert the probe?

Re: Tired of being heard from 2 counties over...
 

Have you seen this ?

https://cimg2.ibsrv.net/gimg/www.thi...a843d08825.jpg

Re: Tired of being heard from 2 counties over...
 

After looking at a video on their web site, it looks like their mufflers are a glass pack with a cap bolted over the end and a variable number of spacers to let the exhaust out. I don't think that would give me the flow I need unless I just left off the cap...then it would just be an expensive glass pack.

Re: Tired of being heard from 2 counties over...
 

No I have not seen that. Who makes it?

My first thoughts are that it is filled with fiberglass and that moving parts, subjected to hot exhaust gasses, are likely to break.

But that aside, it looks like an interesting idea.

Re: Tired of being heard from 2 counties over...
 

Really only in the sense that with the rest of their components, i.e. LS headers, trans crossmember and engine mounts, it all bolts together.
But like any dual exhaust with these 3rd gens, we're forced to fabricate. There are a few members here that have adapted this Holley/Hooker BlackHeart system by building the intermediate section.
The ground clearance would be a by-product of the crossmember used and the skills of the fabricator.
It may be my eventual route. As things have it, I was forced into the Holley crossmember (due to a transmission change) and that (crossmember) allows for significant clearance. Compared to my single 3" (from the transmission mount back) the 2 x 2.5" plus two mufflers offers a significant increase in flow.
I understand that's not the packaging you're looking for but from a performance potential, short of a couple of "turbo" mufflers dumping before the rear axle (as in old school) I think that's about as good as gets. Maybe a single 4" and a massive muffler would offer greater CFM but almost certainly at the cost of noise.
I'm not sure if the Hooker mufflers are packed or baffled.

Re: Tired of being heard from 2 counties over...
 

2x 2.5" =9.8 square inches
1x 3" =7.06"
2x 3" =14.1"
1x 3.5" =9.6" (easier routing over the axle)
1x 4" =12.5" (ovaled over axle?)

No doubt that dual 2.5" would flow better than what I have now.

But if I were to mod my exhaust, I think that I would just replace the over axle 3" with an ovaled 4". Then split it into two 3" for mufflers and tail pipes.

I'm pretty sure that my current y-pipe (forward of the Y, just before the rear axle) flows better than 2x2.5" would. The single 3" section going over the axle and to the muffler is the choke point.

Maybe I should look into getting a pair of 3" x 12" bullets and using the "Y" I have. Then dual 3" tail pipes...which might also have room for 2 more 12" bullets. I'll have to think on that...

Re: Tired of being heard from 2 counties over...
 

If I'm not mistaken, someone makes an over the axle 4". Like the Hooker 2 x 2.5", it's necessary to modify the panhard support for clearance. The mod isn't difficult from what I've seen. It may be Mufflex...
Your idea of a pair of 12" bullets in place of a traditional oval muffler case (in the OEM location) is similar to my own. And one I think could be effective. Whether to add another pair of bullets is something I hadn't considered but has some merit. Certainly it would quiet things down somewhat. The packaging may be difficult though.

EDIT: It is Mufflex. But from the website, I can't determine how it goes together.

https://www.mufflex-performance.com/...gle-cat-system

Re: Tired of being heard from 2 counties over...
 

I've seen the Mufflex system before. But I would like to use 4" tubing and squish it into an oval. It should still flow better than dual 2.5" pipes but be easier to fit.
Once over the axle, it would split into two 3" pipes for the mufflers.

Re: Tired of being heard from 2 counties over...
 

Round 4" will fit fine over the axle with a panhard relocation bar\bracket.

Link: https://www.foundersperformance.com/...maro-firebird/

It looks pretty, too.

Re: Tired of being heard from 2 counties over...
 

That's what I figured. The mod isn't much either.

Re: Tired of being heard from 2 counties over...
 

I'm not sure I like that mod.
From what I have seen it amounts to adding spacers between the panhard rod brace and the body. With the kind of cornering stresses I subject my car too, I'm not very comfortable with that.

I would probably just use a custom 4"+ oval pipe that will fit without moving things around. But that is a lot of work and what I really want now, is to see if I can quiet it down some without increasing the back pressure.

Re: Tired of being heard from 2 counties over...
 

That is true regarding the relocation mod. At least in as much as the way Hooker does it with their dual exhaust kit. I don't care much for it either.
Now this wouldn't be instant gratification by any stretch but there's the UMI relocation kit. It not only offers the added clearance by way of a replacement panhard support brace but also offers the advantage of relocating the panhard bar itself to a location that provides better chassis dynamics (at least in the way it's been explained to me by people who road race these platforms: lowered panhard mount and extended ball joints round out the package regarding roll centres)

http://umiperformance.com/catalog/in...roducts_id=289

Re: Tired of being heard from 2 counties over...
 

Maybe...but pretty much any kind of suspension mod is always a compromise. It will help in some situations and hurt in others. Not that I'm against suspension mods. I have too many to count. But once you get past the basic mods (strengthening and play removal), they have less and less real world improvement and more and more complications.

I also like the UMI setup a lot more than the Hooker way.

But I don't think that it is for me...at least not right now.

Re: Tired of being heard from 2 counties over...
 

DynoMax VT. I liked the idea. Early ones had a rattle in the valve, but they seemed to have fixed that in later ones.

Doesn't appear they make it anymore?

http://www.dynomax.com/mufflers/

Re: Tired of being heard from 2 counties over...
 

I was doing some searching. Check out these options:

MagnaFlow Performance mufflers are 100% stainless steel and lap-joint welded for solid construction and rugged reliability even in the most extreme conditions. They feature a free-flowing, straight-through perforated stainless steel core; stainless mesh wrap and acoustical fiber fill to deliver that smooth, deep tone.

http://pypesexhaust.com/c-702451-muf...-mufflers.html

http://pypesexhaust.com/i-13475156-m...s-mvr203s.html


http://pypesexhaust.com/files/muffler-compare.jpg

http://www.vibrantperformance.com/ca...Path=1527_1032

Vibrant even has TITANIUM mufflers and pipes.

Re: Tired of being heard from 2 counties over...
 

Its that "Acoustical fiber fill" that you have to watch out for. It generally (Always?) is not stainless steel. And even if it were stainless steel, from what I've read from various sources, it will also eventually suffer from metal fatigue from the constant vibration, break apart into tiny pieces, and fly away.

That's the rub, it seems like all of the "straight through" mufflers rely on some sort of fiber packing to deaden sound, and fiber packing, no matter what it is made from, has a limited life span.

That means that a $300 titanium muffler may not have an effective muffling life span, that is any longer than a $50 glass pack.

My current thinking is that, for a straight through muffler, either cheap and easily replaced, or "re-packable" is probably the way to go.

So far I've only seen one that was "re-packable" and I don't remember where, as I didn't think much of it at the time.