Is 2 mufflers better than 1?
11-10-2010, 07:50 PM
#1
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Is 2 mufflers better than 1?
Hey guys just had a magnaflow single muffler with tip put on my car, and i just wanted to get some opinions as far as looks and what people think about going single muffler design vs 2. I had the magnaflow kit before with dual exhaust, I did notice that the single can was abit less high pitched and not as loud maybe because the exhaust cans are different dimension. As far as performance, can't really tell right now because i had stock, I know i definitely saved some weight. oh and my exhaust shroud did melt alittle 
with the single can.
with the single can.
11-10-2010, 08:31 PM
#4
What I get is that the bigger the volume of the muffler(s), the lower the back pressure for a given noise reduction. For the -8, a single (like the stock), has considerably more working volume than the typical dual models, so it's gonna be more efficient. The single vs dual outlet considerations are less clear to me in terms of efficiency, but since for a single outlet, all the heats going thru one tip, it makes sense that shroud melting might become a problem.
11-10-2010, 08:56 PM
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I do agree somethings come better in a pair 
, for a rotary engine just not quite sure. past rotary had a single can, i think its just for looks on an rx8 . or maybe better head dissipation.
Yea i was going to get an HKS, but i hear its very very loud and its not very street legal, but then again half the things i do on my 8 isn't very legal. at least in california. I went this way also because my buddy owns the shop so i got a really good price with it less than half of what i would pay for for a single can HKS. I'm going to do more road testing and some autocrossing with this setup i'll report more when i get more testing done. Yea i did cut the melted plastic, i hope that i won't run into anymore issues with melting plastic o.O.
, for a rotary engine just not quite sure. past rotary had a single can, i think its just for looks on an rx8 . or maybe better head dissipation.Yea i was going to get an HKS, but i hear its very very loud and its not very street legal, but then again half the things i do on my 8 isn't very legal. at least in california. I went this way also because my buddy owns the shop so i got a really good price with it less than half of what i would pay for for a single can HKS. I'm going to do more road testing and some autocrossing with this setup i'll report more when i get more testing done. Yea i did cut the melted plastic, i hope that i won't run into anymore issues with melting plastic o.O.
11-12-2010, 04:00 PM
#8
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As long as your muffler can flow what the engine requires, there is no performance advantage between a single vs a dual muffler.
Looks are subjective. I tend to think that if a car is shaped for 2 exhaust tips as the RX-8bumper is, that it should have 2 exhaust tips. That is just my opinion though. Other people like the look of just one, even on a car that originally had 2.
In terms of sound, 2 is theoretically quieter. You have twice the muffler area over the same amount of sound. You can actually run 2 smaller mufflers, in terms of pipe area, as opposed to a single muffler and have the same amount of flow. This would also mean quieter still.
2 mufflers adds weight, complexity, and costs more.
Hopefully that is a fairly unbiased answer.
Looks are subjective. I tend to think that if a car is shaped for 2 exhaust tips as the RX-8bumper is, that it should have 2 exhaust tips. That is just my opinion though. Other people like the look of just one, even on a car that originally had 2.
In terms of sound, 2 is theoretically quieter. You have twice the muffler area over the same amount of sound. You can actually run 2 smaller mufflers, in terms of pipe area, as opposed to a single muffler and have the same amount of flow. This would also mean quieter still.
2 mufflers adds weight, complexity, and costs more.
Hopefully that is a fairly unbiased answer.
11-12-2010, 04:16 PM
#9
11-12-2010, 04:26 PM
#11
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I hated it before the BHR pipe, too loud and not a great tone. Now it's not quite as loud (probably too loud for most) but the tone is perfect. It sounds like a GSXR at WOT. The only time is sucks in when I am going slow and have to go up a hill, the load at low RPM's makes it deep and loud. I am sure the house at the hill entering my street hate me, 
But I am respectful and coast most of the way through the neighborhood.
But I am respectful and coast most of the way through the neighborhood.
11-12-2010, 05:12 PM
#12
Trained true Killers
Ok were to start, lets say you have a v8 that means you have two headers and then in that case you would be able to use a true dual exhaust running a single pipe of each header that would = more flow. We have one header therefor in order for us to get better flow we would need to find the shortest less restrictive route to get the spent gases from motor to the ground. Now by nature a muffler's job is to restrict the flow in order to meet sound restrictions. In order to do this they use a series of baffles that are welded inside the muffler that channel the gas throw the muffler like a maze causing a whole lot of restriction. Therefor two mufflers on one pipe would equal twice the restriction. Duals on a RX are dual mufflers not a true dual exhaust purely for show not go
11-12-2010, 05:55 PM
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Ok were to start, lets say you have a v8 that means you have two headers and then in that case you would be able to use a true dual exhaust running a single pipe of each header that would = more flow. We have one header therefor in order for us to get better flow we would need to find the shortest less restrictive route to get the spent gases from motor to the ground. Now by nature a muffler's job is to restrict the flow in order to meet sound restrictions. In order to do this they use a series of baffles that are welded inside the muffler that channel the gas throw the muffler like a maze causing a whole lot of restriction. Therefor two mufflers on one pipe would equal twice the restriction. Duals on a RX are dual mufflers not a true dual exhaust purely for show not go
Just curious as you how you figure that 2 wide open mufflers with no ballfles (ie magnaflow) would be more restrictive that 1 of those same mufflers? That really makes no sence to me. I get that the load will be split between the 2 mufflers, but the sum of air being discharged by both should be same same as the air being discharged by the 1. If not, then where is the exhaust gas going?
Has anyone ever cut an 8's stock muffler open? It's really the only muffler I've seen that has the inlet in the middle of the muffler. I would be interested to see what the internals look like.
11-12-2010, 06:08 PM
#14
Trained true Killers
[quote=Sixsix;3782595]Just curious as you how you figure that 2 wide open mufflers with no ballfles (ie magnaflow) would be more restrictive that 1 of those same mufflers? That really makes no sence to me. I get that the load will be split between the 2 mufflers, but the sum of air being discharged by both should be same same as the air being discharged by the 1. If not, then where is the exhaust gas going?
Ok I dont have time argue but if you would like email one of the many Rolex series RX8 race teams and tell them that they should split there single exhaust with a y therefore forcing the fumes to travel a greater distance before exiting out the back please do so.
Ok I dont have time argue but if you would like email one of the many Rolex series RX8 race teams and tell them that they should split there single exhaust with a y therefore forcing the fumes to travel a greater distance before exiting out the back please do so.
11-12-2010, 06:12 PM
#15
Trained true Killers
Thats funny you said that I have my stock one just siting around taking up space. I have been wanting to chop into it to see how they built it, I might just do that now
11-14-2010, 10:06 PM
#20
its not about how many, its about how much air flow your getting. our car could probably get away with one pipe. Look at some of the high performance engines in pick up trucks running one 4inch pipe instead of say two, two inch or two three inch.
11-15-2010, 09:03 AM
#21
Registered
I think that's pretty well understood. All things being equal 2 is theoretically quieter due to double the dampening area. If you take a car that has 1 muffler, and then split the exhaust so now it has 2 of the exact same muffler, theoretically it should be quieter. The one caveat to that scenario is that with a second muffler you also have greater area for the exhaust and hence noise to exit out of which may offset it somewhat. Then again that exhaust is of lower velocity going through that larger area which means there is less energy in that same area. Obviously 2 straight through fart can ricer mufflers are going to be louder than 1 large chambered muffler. That isn't an equal comparison though.
11-15-2010, 09:15 AM
#22
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Now by nature a muffler's job is to restrict the flow in order to meet sound restrictions. In order to do this they use a series of baffles that are welded inside the muffler that channel the gas throw the muffler like a maze causing a whole lot of restriction.
There are some straight through mufflers which are actually quite restrictive. There are also some mufflers which are chambered which aren't restrictive at all. Having baffles does not automatically mean restriction and have none does not automatically mean it is free flowing. If you have a straight through muffler that has a louvered core, much like most loud ricer style mufflers, these things are terribly restrictive and don't quiet much. They are pretty much everything wrong that can be done in muffler design. Then to help quiet them, people install restrictive plugs in the end. These mufflers make less power than any stock muffler out there and they can't even quiet it. They are the antimuffler. Why people pay money for these things I have no idea.
The larger a muffler is, the better it silences. Obviously this is NOT a comparison of muffler A vs muffler B but rather to say that if we have 2 mufflers of the exact same design internally and with the same sized core but one of them is physically larger with more sound absorbing material, that one will be quieter. It will also have a deeper and tougher sounding tone. This is another reason why straight through can style mufflers typically don't sound all that good.
There is a lot more to muffler design that just making it restrictive so it makes it quiet. That isn't necessary and in many cases mufflers may do neither. They don't have to be restrictive to make the exhaust quiet though.
11-15-2010, 09:23 AM
#23
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My preference for single vs dual mufflers really comes down to what the car looks best with and not what I think will make more power or quiet better. We know each can do very well in both regards. If a car came with 2 mufflers and has the bumper cutout for 2 mufflers, it only looks good with 2 mufflers. If the car was only intended to have 1 muffler and only has the cutout for one, it needs to stay single. It just looks plain bad any other way.
11-16-2010, 06:07 AM
#24
Here's how to make a very quiet, zero-baffle exhaust: a straight, expansion - tapered pipe, 100 feet long. Why? Noise comes differences in pressure, coming here from the difference in the port open and port closed condition. Secondarily, it comes at the tip from the difference in pressure between the moving exhaust and the air outside the exhaust. The longer the distance travelled, the more the high pressure pulses dissipate into their low pressure neighbors. Also, the exhaust stream is cooling as it moves. As it cools, it becomes denser and the velocity drops (the constant in the system is mass flow; denser gas requires less velocity to flow the same mass). Expanding the pipe, helps reduce the flow velocity as well.
A 100 ft long exhaust system doesn't work for a car (but similar systems installed in old spy planes has). However this is well simulated in the RX-8 muffler. Increasing the diameter hugely over the incoming pipe reduces temperature and slows the flow speed which allows time for both further cooling and for pressure pulses to dissapate. Baffles also increase the path length, as well a creating self-cancelling reflections. (Shorter mufflers don't have the space to cancel low-frequency sounds which is why they tend to deepen the sound; a deeper sound may be more pleasing, but doesn't directly imply better performance). The fact that stock does a much better job in noise reduction is strongly hinted by lower tip temperatures than my Greddy SP-2 system. If one wanted a single exhaust as noisy as a SP-2, reduced baffling would achieve that with a lower resulting back pressure (cause the physics are better in the single configuration.)
Dual mufflers (in parallel) came from V-x engines with dual cylinder banks. A double exhaust allowed a certain mechanical simplicity which avoided sharp bends. To give a dual exhaust on an RX, usually sharp bends are added. Dual tips are an exercise in styling, not performance. Single entrance, single exit, large diameter and long mufflers will trump short small duals every time (assuming x amount of noise reduction).
A 100 ft long exhaust system doesn't work for a car (but similar systems installed in old spy planes has). However this is well simulated in the RX-8 muffler. Increasing the diameter hugely over the incoming pipe reduces temperature and slows the flow speed which allows time for both further cooling and for pressure pulses to dissapate. Baffles also increase the path length, as well a creating self-cancelling reflections. (Shorter mufflers don't have the space to cancel low-frequency sounds which is why they tend to deepen the sound; a deeper sound may be more pleasing, but doesn't directly imply better performance). The fact that stock does a much better job in noise reduction is strongly hinted by lower tip temperatures than my Greddy SP-2 system. If one wanted a single exhaust as noisy as a SP-2, reduced baffling would achieve that with a lower resulting back pressure (cause the physics are better in the single configuration.)
Dual mufflers (in parallel) came from V-x engines with dual cylinder banks. A double exhaust allowed a certain mechanical simplicity which avoided sharp bends. To give a dual exhaust on an RX, usually sharp bends are added. Dual tips are an exercise in styling, not performance. Single entrance, single exit, large diameter and long mufflers will trump short small duals every time (assuming x amount of noise reduction).
Last edited by HiFlite999; 11-16-2010 at 06:13 AM.
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