Exhaust bypass valves explained

[rb92gt]

A current limited diode would be like a pressure relief valve, which I suspect is not present in the GT350 exhaust. No, Fluid Mechanics dictates that each "leg" of the exhaust has it's own flow impedance curve. This curve is characterized by the function: Pressure Drop = Constant x (Flow Rate)^power. The power is usually between 1.7-2.0. For the loud side, the constant and power is lower than on the quiet side (because there is less restriction), so the flow impedance curves have a similar shape, but the loud side is much more gradual, as pressure drop rises with flow rate. Thus, at high flow, the restriction of the quiet side increases much faster, resulting in continuously lower flow. I stand by my initial analysis.

Holy hell guys, this is some next level kind of stuff here. A muffler is a metal box with a few pipes coming out of it, in our case one pipe in the front and two in the back. One in the back has a valve that opens and closes, the other does not.

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[Demonic]

More accurately, from a relativistic standpoint the muffler is like Schrodinger's box and the exhaust baffle a flux capacitor inside Schrodinger's box. The exhaust going in doesn't actually know whether the baffle is open or not. Flipping the switch to open allows the Flux capacitor to open a 4th dimension shortcut where the exhaust 'sees' the bypassed baffle prior to the baffle actually opening, thus allowing the exhaust to maneuver inside Schrodinger's box while those of us outside the box can't know the path inside. The increased heat from the exhaust then burns Schrodinger's cat, which is why the signature voodoo sound can't be replicated - because it's actually the sound of a cat scratching the inside of a 4th dimensional box, sending ripples through space-time.

 

[rb92gt]

More accurately, from a relativistic standpoint the muffler is like Schrodinger's box and the exhaust baffle a flux capacitor inside Schrodinger's box. The exhaust going in doesn't actually know whether the baffle is open or not. Flipping the switch to open allows the Flux capacitor to open a 4th dimension shortcut where the exhaust 'sees' the bypassed baffle prior to the baffle actually opening, thus allowing the exhaust to maneuver inside Schrodinger's box while those of us outside the box can't know the path inside. The increased heat from the exhaust then burns Schrodinger's cat, which is why the signature voodoo sound can't be replicated - because it's actually the sound of a cat scratching the inside of a 4th dimensional box, sending ripples through space-time.

That's it, I'm going to bed. My brain hurts. :lol::headbonk:

 

[dwalker]

If the OP couldn't figure out that the valve closes to block the straight through section of the muffler (making it quiet) and then opens to let it go through there unmuffled (is that a word?), then you guys have just made his head explode....:lol:

 

[AndreiD]

Just to be clear, there is ALWAYS some exhaust going through the muffler through one pipe on each side. This pic shows what we are all trying to say, the outside pipes always have flow through the muffler to quiet exhaust. The inner pipes with baffles let exhaust essentially bypass some muffling when open (an internal pic would be best, can't find one).

Thanks for clearing things up. :hail:

 

[AndreiD]

So what's really your concern OP? I'm confused. Or are you just asking?

Yep, just asking. I have all kind of curiosities ;) Sorry if I came with dumb quesitons :cheers:

 

[AndreiD]

A current limited diode would be like a pressure relief valve, which I suspect is not present in the GT350 exhaust. No, Fluid Mechanics dictates that each "leg" of the exhaust has it's own flow impedance curve. This curve is characterized by the function: Pressure Drop = Constant x (Flow Rate)^power. The power is usually between 1.7-2.0. For the loud side, the constant and power is lower than on the quiet side (because there is less restriction), so the flow impedance curves have a similar shape, but the loud side is much more gradual, as pressure drop rises with flow rate. Thus, at high flow, the restriction of the quiet side increases much faster, resulting in continuously lower flow. I stand by my initial analysis.

 

[AndreiD]

If the OP couldn't figure out that the valve closes to block the straight through section of the muffler (making it quiet) and then opens to let it go through there unmuffled (is that a word?), then you guys have just made his head explode....:lol:

Let me ask you what kind of muffler we have on our GT350. Is it a chambered, turbo or straight through?

 

[lemers]

Let me ask you what kind of muffler we have on our GT350. Is it a chambered, turbo or straight through?

Did the dealer remove or modify you exhaust to meet Romania/EU noise limits?

 

[dwalker]

Let me ask you what kind of muffler we have on our GT350. Is it a chambered, turbo or straight through?

Looking at this image, and with the dramatic change of sound when the valves are opened, I bet it's safe to say that the valved portion of the muffler is straight through (highlighted with the red line). But I'm not sure exactly what they did with the outer pipes in order to quieten it down while the valves are closed (without physically cutting open one of these mufflers and seeing, of course).

 

[AndreiD]

Did the dealer remove or modify you exhaust to meet Romania/EU noise limits?

Yep. The fucker cut the exhaust and replaced the stock midpipe with a shitty boxy nasty looking crap. That didn't bother me at all but what bothered me is that he didn't say shit before I got the car.

I found that he put the original GT350 midpipe inside the trunk. I called him and he said that with the stock midpipe the GT350 would not pass the noise regulations of the EU.


[ame="https://vimeo.com/219659828"]And here is the gutted sound in loud mode!!!![/ame]

 

[AndreiD]

Looking at this image, and with the dramatic change of sound when the valves are opened, I bet it's safe to say that the valved portion of the muffler is straight through (highlighted with the red line). But I'm not sure exactly what they did with the outer pipes in order to quieten it down while the valves are closed (without physically cutting open one of these mufflers and seeing, of course).

Well to my understanding, limited as it is, there are 3 type of mufflers. [ame="[MEDIA=youtube]30JJSXWKIC8[/MEDIA]"]Here's an explanation of how each works and how each one of them kills the sound in different ways.[/ame]

 

[Zombo]

Looking at this image, and with the dramatic change of sound when the valves are opened, I bet it's safe to say that the valved portion of the muffler is straight through (highlighted with the red line). But I'm not sure exactly what they did with the outer pipes in order to quieten it down while the valves are closed (without physically cutting open one of these mufflers and seeing, of course).

Most likely, the pipe inside the muffler, represented by your red line, is perforated with holes. When the valve is closed, the exhaust passes thru these holes and follows a less direct path, thru sound reducers/absorbers of some type to the outer exhaust tip.

Another option would be there isn't even a pipe there. The exhaust enters the muffler and flows thru the path of least resistance. With the valve closed, that would be out the quiet side. With the valve open, that would be both paths, with a progressively larger percentage of the flow exiting the loud side as RPMs and flow increases.

 

[AndreiD]

Most likely, the pipe inside the muffler, represented by your red line, is perforated with holes. When the valve is closed, the exhaust passes thru these holes and follows a less direct path, thru sound reducers/absorbers of some type to the outer exhaust tip.

We might never know unless someone decides to section cut their muffler. I'd do it myself if I had a final aftermarket exhaust but I like alot the sound the stock one produces and I like the valve option.

 

[lemers]

Here is a picture of the FP by Borla Exhaust for the GT350. This should be close in design.

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