That 17749 looks pretty goodMy stainless fabricator does great work with the TIG but I don't mind having him modify something if its going to sound better. I'll have him do some 3" v-bands on both sides this time which might make it easier to replace the next set of mufflers if needed.
If it necks down a little, thats fine but I just didn't want to go with something thats dual 2.5 muffler that restrict. Another thing I might do down is forced induction which means I need a good free flowing exhaust. Thats the biggest reason I did dual 3" and not 2.5"
Ok good to know. Thanks!
You are correct. If I had a single 3" with a more stock like engine, my Magnaflow would probably be fine. The cam it has seems to lope a little causing a fair amount of loudness. I don't mind a little at idle, just need to remove the drone and rasp at high RPM. It literally sounds like I have some Cherry Bomb glasspacks. And yeah, the bigger the body of muffler, the quieter it will be so I'm trying to find some big uns!
Ok good to hear. I was considering those or the 50 series. I thought the 70s were the quietest but from reading below, maybe not.
I looked into Thrush but the turbo mufflers didn't have the horseshoe thing the super turbos have for flow. How did you like the flowmaster 50? Loud? Quiet?
I looked those up and watched some videos of cars with dual exhaust and no cats. Seems a little loud from what I watched. Lots of these cars have some big cams though which I'm sure is not helping with being quiet. I wish there was a standard decibel test on every muffler produced. Idle and WOT test.
Ok good to hear. I think the single itself REALLY quiets things down which I can't do unless I want to change the entire stainless exhaust I just built. The dual 3" exhaust will make any muffler loud.
Great info. Thanks! Eventually I will have forced induction weather it be a supercharger or turbo. I realize the headers will have to go with the turbo idea but I didn't want to have to change the entire exhaust for any FI upgrade. Might as well go big to begin with. Anyway I will look into the flowmaster 50 bigblock. I do agree they aren't the best for flow. I've seen dynos with flowmasters compared to other mufflers and its not that impressive. That being said, I'm more worried about making quiet now so if I have to give up some tq/hp so be it.
Good to hear. I think I can fit them. My current mufflers are 24" body and 28" in total length. Thanks!
Thanks !I USE to have a big block but went back to a 406 SBC. My initial goal was twin turbos and make some killer HP with this Dart Block/AFR combo but had to scrap the idea after we signed on a new house build and I had to hurry to get the project running so the turbo idea went on the back burner for now. I do realize the smaller pipe helps but would rather not do that since it would require to scrap my entire stainless exhaust system. I think there are some 3" mufflers out there that will help.
I did come across this old article from a Pontiac site.
https://pontiacstreetperformance.com/psp/exhaust.html
Shows the mufflers flow and sound levels. It is pretty old so some are not being made these days. But look at the 17749 Dynomax Super Turbo. Seems to flow well and is quiet. That would probably be the offset/offset design that looks to have the best flow internally.
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My quest for quiet, free flowing mufflers
- Thread starter Shawn
- Start date
Just keep in mind that chart is optimistic. I guarantee if you have 460 HP and you cap it with a 2.5" dual system you will lose HP vs a 3" system. And I don't believe you will get all of your 679 ponies out of a dual 3" either. I would be going dual 3.5 for that and dual 4" for 800. I have a calculator in my app that calculates suggested header primary diameter based on a target exhaust velocity and it calculates exhaust diameter based on HP and flow of a pipe (assuming flow through mufflers).
Here is what I would recommend, you can round down or up depending on whether you prefer performance or quietness. These are ODs for 16 gauge exhaust pipe, single or dual exhaust. Now obviously if you have a supercharger this is important, and if you have a turbo or two you can get away with smaller because the turbo takes some energy and heat out of the exhaust. For turbos I would recommend leaving the pipe the same diameter as the exhaust outlet on the turbine for maximum performance.
HP - DUAL - SINGLE
400 - 2.7 - 3.8
500 - 3.0 - 4.2
600 - 3.3 - 4.6
700 - 3.6 - 5.0
800 - 3.8 - 5.3
900 - 4.0 - 5.6
1000 - 4.25 - 5.9
Here is what I would recommend, you can round down or up depending on whether you prefer performance or quietness. These are ODs for 16 gauge exhaust pipe, single or dual exhaust. Now obviously if you have a supercharger this is important, and if you have a turbo or two you can get away with smaller because the turbo takes some energy and heat out of the exhaust. For turbos I would recommend leaving the pipe the same diameter as the exhaust outlet on the turbine for maximum performance.
HP - DUAL - SINGLE
400 - 2.7 - 3.8
500 - 3.0 - 4.2
600 - 3.3 - 4.6
700 - 3.6 - 5.0
800 - 3.8 - 5.3
900 - 4.0 - 5.6
1000 - 4.25 - 5.9
beags86
Eastbound and Down
Even if that chart is a bit optimistic,
Its probably good enough for the average guy.
It looks like your app takes a more scientific approach vs that chart is basing it off known pipe sizes.
I can appreciate both approaches.
So do you have 4.5 inch duals on the regal then?
Dual 5" oval which flows about the same as 4.5" round yes.
The 5" oval mufflers are not quiet. I think I will get some Borla 3" straight through, and put two on each side in parallel, so I have the flow of four 3" pipes but a little bit quieter than it is now. I just don't have the money to buy 4 Borla mufflers right now, ha ha
The 5" oval mufflers are not quiet. I think I will get some Borla 3" straight through, and put two on each side in parallel, so I have the flow of four 3" pipes but a little bit quieter than it is now. I just don't have the money to buy 4 Borla mufflers right now, ha ha
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I did 1003 hp at the wheels with single 4" on a 4 banger. I probably could have made more with dumping out the hood but it was a street car.
4" Varex remote muffler was quiet too but very restrictive when closed. Mustang dyno.
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That's pretty good! I'm curious what fuel you were using for that?
You have shown proof my numbers are naturally aspirated or Supercharged. For turbos you want to keep the same diameter as the outlet of the turbine or larger to let the turbine spool freely without restriction or back pressure, which it appears you did from your picture.
But also, I am not saying you can't make more power with a restricted exhaust, you can put a dual 2.25" on a 600 hp NA big block and still make 550 HP or more possibly. I'm just saying you are sacrificing performance if you go smaller, limiting your power with a bottleneck. If you want a true performance potential of the engine that is what I suggest. I think your dual 3" is good right now, I wouldn't go smaller.
You have shown proof my numbers are naturally aspirated or Supercharged. For turbos you want to keep the same diameter as the outlet of the turbine or larger to let the turbine spool freely without restriction or back pressure, which it appears you did from your picture.
But also, I am not saying you can't make more power with a restricted exhaust, you can put a dual 2.25" on a 600 hp NA big block and still make 550 HP or more possibly. I'm just saying you are sacrificing performance if you go smaller, limiting your power with a bottleneck. If you want a true performance potential of the engine that is what I suggest. I think your dual 3" is good right now, I wouldn't go smaller.
E85 fuel, 40psi of boost, mile high elevation. For turbos you always want to go larger than the turbine housing outlet and zero back pressure. Having no exhaust at all after the turbo is the best for max power (dumping out hood or fender). Totally agree with you on the smaller exhaust size being the bottle neck. I have learned if you can fit the bigger exhaust tubing, do it but it does make things louder.
beags86
Eastbound and Down
You don't want back pressure in any system.
Who ever started that old tale needs to be drug out into the street and shot.
Well you need some. But that “some” is also created at the first bend in the pipe and the pipe wall friction. There’s a couple of great books out there about exhaust theory. All fascinating
Each one says about the same though, the “needed” back pressure is well beyond met before you get to any muffler/resonator/cat
Each one says about the same though, the “needed” back pressure is well beyond met before you get to any muffler/resonator/cat
beags86
Eastbound and Down
beags86
Eastbound and Down
Got any of those book titles?
Have one at home. It’s more theory, and less Chevy related, but full of science stuff
One I apparently lent out and can’t remember who to. Believe the book may have been by David Vizard. Need to call the old man and see if he has the 3rd. Both of these had big boy engine references.
Of course engine masters has videos on all this stuff. A lot less dry than reading it
One I apparently lent out and can’t remember who to. Believe the book may have been by David Vizard. Need to call the old man and see if he has the 3rd. Both of these had big boy engine references.
Of course engine masters has videos on all this stuff. A lot less dry than reading it
beags86
Eastbound and Down
Yeah i watch all that stuff, but sometimes they don't turn over every stone. I also have a few high performance building books in my shop already, and didn't know if you were maybe talking about a book I may already have.
I love engine theory stuff.
Feel free to share those titles as well.
@Shawn and I talked about a lot of this last year, I need to bookmark the post in my build thread for cross reference
Good stuff
A video they did last season was strictly a muffler design comparison and showed that a turbo type muffler can rob 30 hp or more.
Go find thatA video they did last season was strictly a muffler design comparison and showed that a turbo type muffler can rob 30 hp or more.
beags86
Eastbound and Down
Looks like its not on YouTube.
But hes right, the turbo muffler is terrible for performance and should not be considered by anyone that cares about power.
