Glass Packs as Resonators

[Belgian1979]

Most of the glass packs I've used are perforated tube so not directional. They do work well when you get some length and volume.

Agreed. But it depends on what you want to have in terms of sound. Smaller volume attenuates at lower speeds but gives off brutal sound at higher engine speeds.

i ran two short hot dog cylindrical resonators in parallel part way down the exhaust on a twin exhaust system and it was terribly droney at low rpm.
So i designed a bigger volume one basically joined them like an oval twin in and out straight through muffler and it was significantly better. due to space restrictions the length had to remain about the same and it was maybe a 2" longer body. i am not sure if having the two pipes being able to someone communicate with each other (each pipe is connected to the same volume stuffed with glass and stainless wool) had any effect.there was an existing rear muffler that remained the same

Joining exhausts of opposite banks has this effect.

If you have lower volume there is less room for expansion of the gasses. So when rpm increases and exhaust gas volume the muffler is already full due to which most gasses just go straight out. My 0.02$

[digger]

Agreed. But it depends on what you want to have in terms of sound. Smaller volume attenuates at lower speeds but gives off brutal sound at higher engine speeds.

i ran two short hot dog cylindrical resonators in parallel part way down the exhaust on a twin exhaust system and it was terribly droney at low rpm.
So i designed a bigger volume one basically joined them like an oval twin in and out straight through muffler and it was significantly better. due to space restrictions the length had to remain about the same and it was maybe a 2" longer body. i am not sure if having the two pipes being able to someone communicate with each other (each pipe is connected to the same volume stuffed with glass and stainless wool) had any effect.there was an existing rear muffler that remained the same

Joining exhausts of opposite banks has this effect.

If you have lower volume there is less room for expansion of the gasses. So when rpm increases and exhaust gas volume the muffler is already full due to which most gasses just go straight out. My 0.02$

i should mention that i also already had an x-pipe upstream so each pulse was already being sent(split) to both of the separate hotdogs

[FirstEliminator]

https://www.summitracing.com/parts/aph-xs0416

https://www.summitracing.com/parts/sum-630805


These are the two glass packs I am looking at. The Summit has internal louvers and the AP has a perforated core. Which one would have a quieter note?

thanks,
Mark

[pdq67]

I personally would go with the smooth perforated inner pipe glass pack muffler.

And I would try to install as much perforated pipe as I could!

pdq67

[engineguyBill]

Jegs has some short glass-pack mufflers (maybe the same vendor as Summit) that I have used with Walker turbo mufflers. Good results.

[pdq67]

Does W/D/T still sell the long, "side-pipe", smooth perforated inner pipe real glass packs anymore??

pdq67

[dave brode]

Mark,
Fwiw, I'd avoid the louvered version, regardless of direction installed. Although as a pair of mufflers alone, they are loud, the race magnum bullets work well as a resonator. I bet the 18" body would do very well. They now have some in s/s, but way more money than the AP that you showed.

https://www.summitracing.com/search/par ... 20Mufflers

There's also a pricey welded version, similar to the AP that you showed.
https://www.summitracing.com/parts/wlk-17230/overview/

Dave

[MikeB]

Adding Summit Racing brand 12" glass packs to a dual exhaust system in my old pickup with Flowmaster 50 mufflers got rid of most of the drone. Can't speak to power loss, but if I ever do it again, I'd probably use glass packs with 1/4" -1/2" larger pipe diameter adapted to the exhaust pipes.

[pdq67]

I have asked before,. but I don't think that I ever got an answer back?

What would happen if I installed an open expansion chamber shoe box on the intake end of the long, side-pipe W/D/T real glass packs by 1st bell-mouthing and bull-nosing the mufflers intake out to help funnel the exhaust gasses through the muffler???

pdq67

[one finger john]

???

[HotRodRay]

NEW or very long glasspacks sound ok, regardless of design. BUT, BUT, they always get louder, quickly. Often the drone changes.

This year we have a pile of Flowmasters and burned glasspacks removed because the owners hated them.

Stories of Dynamax Super Turbo and Magnaflow with glass indicate they deteriorate more slowly.

I remember one guy had 2 glasspacks on each side, but it sounded wierd after a while.

I have about given up on mine and am seriously considering stock type mufflers... realizing that I don't have 4 cats, the new type mufflers might be (louder) mellow enough ... consistently.

Noise is fun if its a Saturday night deal. After 100 miles it is xxxx.

Oh, by the way.
David Vizard invented the Dynamax Super Turbo. Didn't he?

[ptuomov]

The Borla mufflers that I've used are pretty loud straight out of the box but don't seem to degrade over time, despite the basic design of packed chamber with a perforated tube thru them. This may be partially related to why those Borla mufflers are a little more expensive than most mufflers. in terms of longevity, the packing material is key and to a large extent you seem to get what you pay for.

The straight thru design with a packed chamber seems to be where the industry has converged as far as the universal performance mufflers are concerned. It's a really good at attenuating broad-band noise. Combining that with a tuned resonator to take out any remaining problem frequencies and selecting the pipe lengths sensibly will complete the system. Combining pulses for some distance in a cross-plane V8 also takes out a couple dB.

I think that the Dynamax Super Turbo sort of a design which makes two 180-degree turns is at this point an obsolete design. It was much better than the stock mufflers way back when it was introduced, but time has passed on.

Just opinions, on sound I think its mostly a question of taste and local laws/enforcement.

NEW or very long glasspacks sound ok, regardless of design. BUT, BUT, they always get louder, quickly. Often the drone changes.

This year we have a pile of Flowmasters and burned glasspacks removed because the owners hated them.

Stories of Dynamax Super Turbo and Magnaflow with glass indicate they deteriorate more slowly.

I remember one guy had 2 glasspacks on each side, but it sounded wierd after a while.

I have about given up on mine and am seriously considering stock type mufflers... realizing that I don't have 4 cats, the new type mufflers might be (louder) mellow enough ... consistently.

Noise is fun if its a Saturday night deal. After 100 miles it is xxxx.

Oh, by the way.
David Vizard invented the Dynamax Super Turbo. Didn't he?

[pdq67]

The old-fashioned, "steel-packs", are heavy, but they don't burn out!! You can crush fiberglass in your hands so that is how fragile it is. Add exhaust velocity, heat cycling, and condensed exhaust gas liquids and fiberglass goes away fast.

Are, "smitties", steel-packs? If they are, the only problem with, "smitties", is that they are louvered inner pipe vs perforated and only come in like one inner pipe diameter if not mistaken and it is generally too small for a real high performance engine, imho. Of course, we can parallel them to gain more flow!

I will say that a, "pumpable", refractory ceramic fiber material is made that once heated, hardens into a light-weight monolithic fiber material, but it is pricey! I've played with it in my hands. Neat stuff. I think the hardening agent is no more than, "water-glass"...

pdq67

[FirstEliminator]

Tonight, I put a 14" perforated resonator from AP exhaust on my tail pipe after the axle followed with 10 inches of pipe before the tip of the outlet. I can say -----so far----- the droaning is about 90% gone. I haven't had much chance to spend time driving, but it is dramatically reduced in the range the noise was worst.


thanks for all the replies,
Mark

[pdq67]

Back when I had my .060" over 409 "W" 11.5 to 1 engine in my car, I had a 2.5" x 18", a 12" and a small 2" x 12" real smooth perforated inner pipe glass packs down each side of my '67 Camaro and it was loud to say the least! I loved it!

They were the old but new back then, "can", Woodpecker Thrush mufflers!

pdq67