Making a muffler

[Kevin Johnson]

Here's an empirical question that is relevant for the dimension calculations. Does exhaust gas heat or cool as it goes thru a muffler? I always assumed that outlet was cooler than inlet, but "assume makes an a$$ out of u and me" as they say.

It cools due to heat transfer into the exhaust pipes and mufflers, proportional to internal turbulence, surface area, airflow over the system's exterior, etc. Just for interest I might see if I still have enough thermo-couple wire to plumb my T/C read out into different parts of the system..

Due to chemical activity, exhaust temperature does rise during its passage through a catalytic converter.

Search is your friend. At great expense the US Forest Service made many empirical temperature measurements of pre-catalytic and catalytic exhaust systems along the length of the system for quite a number of different vehicles.


https://www.fs.fed.us/t-d/programs/fire ... _tests.pdf I would have attached the file proper but it is over the max attachments size (2.90MB).

[ptuomov]

Please consider using, "static mixing", technology here if you want to make your exhaust pipes straight through. About 6 or 7 static mixer flutes in a 20" or so long 2.5" dia. straight pipe down each side and go!! If I had the needed welding equipment, I would have this under my car now!!

Otherwise, I like the way, "old-school", WDT, smooth perforated inner pipe REAL glass packs! Suckers are straight through so no back pressure loss at all, imho. Just like DV has shown us. If they are too loud, just add short ones in your exhaust system to act as resonators OR parallel double up on the long ones.. I love their way old school "cackle"!!!

And you haven't lived until you have heard a pair of, "smitties", on a way hopped up 261" 6-banger with split manifolds going up and down through the gears!!
It will raise the, "hair on the back of your neck"!!!
AND you will never forget the sound!!
F**, talk about F-1 crap, no a split-6 turns me on!

Please consider using, "static mixing", technology here if you want to make your exhaust pipes straight through. About 6 or 7 static mixer flutes in a 20" or so long 2.5" dia. straight pipe down each side and go!! If I had the needed welding equipment, I would have this under my car now!! Otherwise, I like the way, "old-school", WDT, smooth perforated inner pipe REAL glass packs! Suckers are straight through so no back pressure loss at all, imho. Just like DV has shown us. If they are too loud, just add short ones in your exhaust system to act as resonators OR parallel double up on the long ones.. I love their way old school "cackle"!!! And you haven't lived until you have heard a pair of, "smitties", on a way hopped up 261" 6-banger with split manifolds going up and down through the gears!! It will raise the, "hair on the back of your neck"!!! AND you will never forget the sound! A split-6 turns me on! You talk about ,"walking the dog", ................

Install WDT perforated inner pipe REAL glass packs! Too loud, then add another pair, end to end, to each side. The suckers are true smooth straight through pipe mufflers here! NO back pressure at all. BUT RUN THE TAIL PIPES OUT PAST THE REAR BUMPER!! Have you ever thought about why the old WDT real glass packs aren't included in any of the muffler tests??? Same deal with why the old Holley 300-36 intake or Weiand 8016 Stealth aren't included in intake manifold tests!!

Me thinks that you are way over thinking this, but, JMHO... Please read me again.. The best we can have are, "straight pipes", but John Law won't allow them. And the old WDT perforated smooth inner pipe REAL glass packs are as close as we can get.

I have two mufflers down each side now, an 18" and a 12" x 2.5" cheap JCW turbo's that exist stock on my '67 Camaro. They were loud on my 406!! And if I live long enough, I am going with as long a muffler string as I can get under my car of the WDT glass packs. Say as long under my floor boards and then cross-wise from each side back by my gas tank like stock. AND the SOB will be straight through!!! I thank DV for his picture of just how real glass packs perform vs box mufflers!

As the old song, "I want to be Bobby's Girl", runs through my mind!! That young Lady could f** sing!!! And don't forget, "Paul and Paula"!!! "Hey, Hey, Paul,---------------"

"Install WDT perforated inner pipe REAL glass packs! Too loud, then add another pair, end to end, to each side. The suckers are true smooth straight through pipe mufflers here! NO back pressure at all. BUT RUN THE TAIL PIPES OUT PAST THE REAR BUMPER!! Have you ever thought about why the old WDT real glass packs aren't included in any of the muffler tests??? Same deal with why the old Holley 300-36 intake or Weiand 8016 Stealth aren't included in intake manifold tests????????

PS., as I like ta say, "You gotta Dime"....

READ ME AGAIN!!!

WDT glass packs don't have anything protruding into the gas stream. They are smooth, perforated inner pipe jobbers! That's why I like them!! Cherry-Bombs and Smitties as well as Purple Hornies, they have sawed louvers in them that protrude into the middle of them if not mistaken?..

Harry, In all respect, just install the old WDT smooth perforated inner pipe glass packs and go!! Too loud, then add either two, "y'd", side by side OR another behind each and go.. AND with tailpipes out past the rear bumper!! I had three glass packs under each side of my old hopped up 409 so know!!

Tell me how you really feel about the glasspack mufflers.

Here's my issue with the glasspack type mufflers with large pipe diameter and small case diameter. The don't take out much of the low frequencies. The case cross-sectional area is too small compared to the pipe cross-sectional area. They do take out higher frequencies, I give them that. But in my opinion, the new Borla and Magnaflow straight-thru mufflers also use stainless steel wool and fiberglass packing to take out those higher frequencies, but because the case cross-sectional area is large compared to the pipe cross-sectional area, they also muffle some of the lower frequencies. It's as if all the muffler makers who spend on R&D concluded that glasspacks do one thing really well and then incorporated a glasspack muffler into all of their large-case mufflers that have big expansion chambers. Given that it's 2017, why would anyone use a basic glasspack muffler that's got a case diameter that is only slightly larger than the pipe diameter, instead of those modern Borlas and Magnaflows and the like?

[j-c-c]

"Given that it's 2017, why would anyone use a basic glasspack muffler....."

Make Exhaust Great again?

[ptuomov]

"Given that it's 2017, why would anyone use a basic glasspack muffler....."

Make Exhaust Great again?

Make Exhaust Loud Again!

[hoffman900]

How the $$ Coast Fab / Burns mufflers look inside:

[ptuomov]

How the $$ Coast Fab / Burns mufflers look inside:

Looks light! Doesn't Burns offer a two-stage or two-chamber muffler for applications that need significant noise control?

http://www.dragzine.com/features/pri-co ... nto-power/

[hoffman900]

How the $$ Coast Fab / Burns mufflers look inside:

Looks light! Doesn't Burns offer a two-stage or two-chamber muffler for applications that need significant noise control?

http://www.dragzine.com/features/pri-co ... nto-power/

I've never see one as everything I'm around doesn't need it or gets away without it (turn it opposite side of the track from the sound guys).

Light is right though:
http://www.coastfab.com/off-the-shelf-m ... sizes.html

[ptuomov]

Doing some speed of sound computations to entertain myself. What's the best estimate of how much the exhaust cools in the exhaust pipe over various distances? I'm talking about at full load when the exhaust pipes and mufflers are sized appropriately for the power (for "no loss" whatever that means).

[englertracing]

Well the purpose of a muffler is reduce acoustic energy output, and those methods have been touched on here in numerous responses, but that acoustic energy is normally converted into heat, and if your alum muffler is effective, it won't be for long, as it starts to drip alum.

you know...... 90% of motorcycle mufflers are made from aluminum.....

[Sir Yun]

I think a 1D sim is the best bet when using just estimations of pipe (not dampers) to get within a few blocks of the ballpark. Otherwise you have to go CFD , proper exhauat software or physically measuring it.

Getting rif of energy using small volumes is pretty hard to do. Big pipes are by definition noisy so use multiples. I'd stay away from stainless for the part that does not need the heat resistance as it tends to have nasty high frequencies.

Maybe look at a RR phantom exhaust system , that is very quiet .

PS
It bugs me no end when people buy a veyron then spend 40k on a "performance " exhaust that is mostly very loud. They spend ages getting it right and quiet then replace it with a shiny loud pipe

[Seanh832]

Im running 4 18" case Dynomax Race Magnum Bullets back to back behind my 434 and turned them out before the rear tires. I love the sound compared to only 2 12" case with tailpipes. I've considered adding Dynatech cone inserts to quiet it down a little more. Im only making a little over 700hp though. Car sounds like big block side pipe Vette on steroids. Very deep tone.

[ptuomov]

Does this temperature, density, and SOS computation look ball park correct?

80 Ambient temperature F
14.7 Ambient pressure psia
459.67 R at zero F
1400 Turbine outlet temperature F
3 Pipe length in m
2 Back pressure psig
0.75 Temperature decay coefficient per m
3.5 Turbine outlet pipe diameter OD inches
0.065 Pipe wall thickness inches

Distance from turbine outlet m, Gas temperature F, Gas pressure psig, Density ratio relative to turbine outlet, Constant velocity flow area sqin, Equiv. single pipe OD inches, Equiv. dual pipe OD, inches Speed of sound m/s, SoS ratio relative to turbine outlet
0.00 1400 2.000 1.000 17.84 4.90 3.50 644 1.00
0.50 1223 1.667 1.083 16.47 4.71 3.37 613 0.95
1.00 1070 1.333 1.167 15.28 4.54 3.25 584 0.91
1.50 937 1.000 1.251 14.26 4.39 3.14 558 0.87
2.00 823 0.667 1.335 13.37 4.26 3.05 535 0.83
2.50 723 0.333 1.415 12.60 4.14 2.96 514 0.80
3.00 637 0.000 1.493 11.95 4.03 2.89 494 0.77

[groberts101]

what about something like the spin-tech mufflers internal designs? Similar to Corsa's "wave travel length" design intentions.. but also implementing some form of packing material? Then hunt for that last bit of needed space for adding a dead-headed j-bend?

[ptuomov]

what about something like the spin-tech mufflers internal designs? Similar to Corsa's "wave travel length" design intentions.. but also implementing some form of packing material? Then hunt for that last bit of needed space for adding a dead-headed j-bend?

I think those chambered mufflers with baffles have a lot of flow losses, they cause back pressure. Seems like a partly perforated tube with packing and a large case is the winning ticket.

There's room for quarter-wave resonators, but I'll just add those at the very last step if there's any drone specifically at some frequencies.

[Carnut1]

166.gif

D.V. artwork. Posted for reference of straight through muffler design. Interesting of what the engine sees this desgn as. This picture was the reason I tortured my neighbors with flowmasters for years. At this point I prefer a aerochamber anti - reversion design especially with a higher overlap cam used on the street. Thanks, Charles