Which unmodified mufflers act as pressure wave termination box?

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ChargerST
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Which unmodified mufflers act as pressure wave termination box?

Post by ChargerST » Fri Aug 10, 2018 7:25 am

Old topic but didn 't really find a lot of answers. Dave Vizard mentions in several articles/books that an open chamber muffler (such as flowmaster 40s) reacts in the same way a pressure wave termination box does (it reflects the pressure waves so that the rest of the echaust system becomes invisible to the engine). I'd rather have just one muffler per side than a termination box and a muffler. So if a muffler can perform as termination box while muffling the exhaust I'd buy that one.
Problem is I don't really like the Flowmaster sound (too tinny imo) - are there any other open chamber mufflers (or other type mufflers which act as termination box) which don't have the typical Flowmaster sound?
Thanks

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Re: Which unmodified mufflers act as pressure wave termination box?

Post by mag2555 » Fri Aug 10, 2018 7:55 am

None that I know of as they overall are just not shaped right, no less what's taking place on the inside!

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Re: Which unmodified mufflers act as pressure wave termination box?

Post by F-BIRD'88 » Fri Aug 10, 2018 8:19 am

Big straight thru perfed pipe mufflers like the Magna flows are the closesed you are going to get to what you want. Minimal or no power loss (sometimes a small gain). Good sound atinuation. . (Usually) best at the back of the car as opposed to right up at the headers. Not a termination box. Can be custom built if needed.

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Re: Which unmodified mufflers act as pressure wave termination box?

Post by ptuomov » Fri Aug 10, 2018 8:40 am

I researched this topic a bit last year. Here’s a long rambling story of it: viewtopic.php?t=49628

In summary, some findings.

First, after an H-pipe, Y-pipe, or X-pipe, the pulses are combined enough that pulse tuning no longer matters much. So the location of xyh may matter but after the cross over nothing else other than flow capacity matters much.

Second, the large case volume, long case length, and large case cross-section area perforated pipe packed mufflers (borla, magnaflow) are the way to go for aftermarket exhaust projects as they work across a broad band of frequencies and therefore are relatively easy to get right the first time without complicated software.

Third, the pipe cross-sectional area should go down as the exhaust gas cools towards the end of the car and the mufflers should be placed as far back as they fit. This is because smaller the ratio of the exhaust pipe area to case cross-sectional area, the greater the effectiveness of the muffler.

Fourth, there was enough speculative research on supersonic shock waves that we included shock wave trap resonators where cats normally are when the car is run without the high-flow cats.
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Re: Which unmodified mufflers act as pressure wave termination box?

Post by Warp Speed » Sun Aug 12, 2018 11:35 am

ptuomov wrote:
Fri Aug 10, 2018 8:40 am
I researched this topic a bit last year. Here’s a long rambling story of it: viewtopic.php?t=49628

In summary, some findings.

First, after an H-pipe, Y-pipe, or X-pipe, the pulses are combined enough that pulse tuning no longer matters much. So the location of xyh may matter but after the cross over nothing else other than flow capacity matters much.

Second, the large case volume, long case length, and large case cross-section area perforated pipe packed mufflers (borla, magnaflow) are the way to go for aftermarket exhaust projects as they work across a broad band of frequencies and therefore are relatively easy to get right the first time without complicated software.

Third, the pipe cross-sectional area should go down as the exhaust gas cools towards the end of the car and the mufflers should be placed as far back as they fit. This is because smaller the ratio of the exhaust pipe area to case cross-sectional area, the greater the effectiveness of the muffler.

Fourth, there was enough speculative research on supersonic shock waves that we included shock wave trap resonators where cats normally are when the car is run without the high-flow cats.
Is the above what you found during back to back testing, or through your research?

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Re: Which unmodified mufflers act as pressure wave termination box?

Post by ptuomov » Sun Aug 12, 2018 1:06 pm

Warp Speed wrote:
Sun Aug 12, 2018 11:35 am
ptuomov wrote:
Fri Aug 10, 2018 8:40 am
I researched this topic a bit last year. Here’s a long rambling story of it: viewtopic.php?t=49628

In summary, some findings.

First, after an H-pipe, Y-pipe, or X-pipe, the pulses are combined enough that pulse tuning no longer matters much. So the location of xyh may matter but after the cross over nothing else other than flow capacity matters much.

Second, the large case volume, long case length, and large case cross-section area perforated pipe packed mufflers (borla, magnaflow) are the way to go for aftermarket exhaust projects as they work across a broad band of frequencies and therefore are relatively easy to get right the first time without complicated software.

Third, the pipe cross-sectional area should go down as the exhaust gas cools towards the end of the car and the mufflers should be placed as far back as they fit. This is because smaller the ratio of the exhaust pipe area to case cross-sectional area, the greater the effectiveness of the muffler.

Fourth, there was enough speculative research on supersonic shock waves that we included shock wave trap resonators where cats normally are when the car is run without the high-flow cats.
Is the above what you found during back to back testing, or through your research?
Thanks for asking for a clarification on this. This is 95% from reading research papers and 5% from testing by John Kuhn. The minimal testing wasn’t very sophisticated, sound pressure level and turboback exhaust pressure. I am planning to record the sound spectrum with and without the exhaust later. The research papers that I read had a lot of interesting test data, and I think I understand a lot better now why the car factories do one thing and borla/magnaflow do another thing.
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Re: Which unmodified mufflers act as pressure wave termination box?

Post by Belgian1979 » Sun Aug 12, 2018 2:55 pm

A question about the change in cross section area of the exhaust pipe towards the muffler : I would think that in a larger diameter pipe, the exhaust travels slower and thus gets more change to dissipate heat and thus reduce the pressure which reduces noise.

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Re: Which unmodified mufflers act as pressure wave termination box?

Post by pdq67 » Sun Aug 12, 2018 11:55 pm

I have two down each side. Cheap JCW, WDM mufflers is all 24" x 2.5" and 18"' x 2.5" on my '67 Camaro and they were still loud..

On my Strong Arm 406..

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Re: Which unmodified mufflers act as pressure wave termination box?

Post by ChargerST » Mon Aug 13, 2018 6:05 am

ptuomov wrote:
Fri Aug 10, 2018 8:40 am
I researched this topic a bit last year. Here’s a long rambling story of it: viewtopic.php?t=49628

In summary, some findings.

First, after an H-pipe, Y-pipe, or X-pipe, the pulses are combined enough that pulse tuning no longer matters much. So the location of xyh may matter but after the cross over nothing else other than flow capacity matters much.
Thanks for your reply - I have some more reading to do.. ;)

Interesting as DV suggests using an H or X pipe before a pressure wave termination box (PWTB). According to the finding you posted a PWTB would only make sense if no cross pipe would be present. Or put it the other way the cross pipe makes the PWTB ineffective (no negative pulses going back to the exhaust valve).
One way or the other it suggest DVs theory is wrong - is that what you mean?
Fourth, there was enough speculative research on supersonic shock waves that we included shock wave trap resonators where cats normally are when the car is run without the high-flow cats.
So this shock wave is seen as a negative impact and not a means of tuning the cylinder filling?

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Re: Which unmodified mufflers act as pressure wave termination box?

Post by ptuomov » Mon Aug 13, 2018 11:10 am

I’m not saying that DV is wrong. I’m just saying that adding or subtracting some pipe length to/from a completely unmuffled system after the first crossover doesn’t do as much to the power and whatnot as adding or subtracting length before the first crossover. Crossover is kind of a termination box by my understanding, and same for catalytic converters. This assumes that the crossover is large, a tiny crossover tube of course wouldn’t do much. Furthermore, I’d caution taking me too seriously as there are people here who’ve done 100x or 1000x as much research and practical exhaust experiments as I have.

The exhaust valve opening shock wave, if it exists, need to be dealt with for noise suppression whether or not its used for to help cylinder filling.
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Re: Which unmodified mufflers act as pressure wave termination box?

Post by xr4x4ti » Mon Aug 13, 2018 11:28 am

Belgian1979 wrote:
Sun Aug 12, 2018 2:55 pm
A question about the change in cross section area of the exhaust pipe towards the muffler : I would think that in a larger diameter pipe, the exhaust travels slower and thus gets more change to dissipate heat and thus reduce the pressure which reduces noise.
In my experience, having two pipes with the same area as one large pump going through the muffler is superior from a noise cancellation standpoint.

Think about it this way, for any given cross sectional area the two pipes have much larger surface area and thus more of the exhaust is exposed to the sound absorbing material.

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Re: Which unmodified mufflers act as pressure wave termination box?

Post by 67RS502 » Mon Aug 13, 2018 1:29 pm

Youre looking for chambered mufflers (volume) not packing mufflers (straight thru like a pipe)
Hooker Aerochambers have volume and a deep sound, since the walls have a foam type inner insulation.
67 camaro
girly rollers on pumpgas:
420 - 641hp BretBauerCam, 1.39, 9.79 @ 137.5
383 - 490hp 224/224, 1.56, 10.77 @ 124.6
502 - 626hp 252/263, 049s 1.44, 10.08 @ 132.7
62 Nova cruiser
383/200-4R/12-bolt w 373s
224/224 HR cam
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Re: Which unmodified mufflers act as pressure wave termination box?

Post by 67RS502 » Mon Aug 13, 2018 1:38 pm

ptuomov wrote:
Fri Aug 10, 2018 8:40 am

First, after an H-pipe, Y-pipe, or X-pipe, the pulses are combined enough that pulse tuning no longer matters much. So the location of xyh may matter but after the cross over nothing else other than flow capacity matters much.
I totally agree.
Most don't understand that the "ideal" exhaust would be correctly sized headers, collectors and collector extensions.
That's all that is needed for most power.
Now in a streetcar we need mufflers, but as long as you have the "ideal" exhaust system, all you need is some volume (terminator box, X, H-pipe)
downstream of it, and a non restrictive system down stream of the Box, X, H-pipe, with the large flow capacity so there is no backpressure.
67 camaro
girly rollers on pumpgas:
420 - 641hp BretBauerCam, 1.39, 9.79 @ 137.5
383 - 490hp 224/224, 1.56, 10.77 @ 124.6
502 - 626hp 252/263, 049s 1.44, 10.08 @ 132.7
62 Nova cruiser
383/200-4R/12-bolt w 373s
224/224 HR cam
1.57 10.97 @ 121.2

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Re: Which unmodified mufflers act as pressure wave termination box?

Post by Belgian1979 » Mon Aug 13, 2018 2:53 pm

xr4x4ti wrote:
Mon Aug 13, 2018 11:28 am
Belgian1979 wrote:
Sun Aug 12, 2018 2:55 pm
A question about the change in cross section area of the exhaust pipe towards the muffler : I would think that in a larger diameter pipe, the exhaust travels slower and thus gets more change to dissipate heat and thus reduce the pressure which reduces noise.
In my experience, having two pipes with the same area as one large pump going through the muffler is superior from a noise cancellation standpoint.

Think about it this way, for any given cross sectional area the two pipes have much larger surface area and thus more of the exhaust is exposed to the sound absorbing material.
Assume going from 2 pipes smaller to 2 pipes bigger. In principle both surface area and flow will have increase

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Re: Which unmodified mufflers act as pressure wave termination box?

Post by NewbVetteGuy » Mon Aug 13, 2018 4:54 pm

ptuomov wrote:
Fri Aug 10, 2018 8:40 am

Third, the pipe cross-sectional area should go down as the exhaust gas cools towards the end of the car and the mufflers should be placed as far back as they fit. This is because smaller the ratio of the exhaust pipe area to case cross-sectional area, the greater the effectiveness of the muffler.
Placement of the muffler as far back as possible if trying to use the mufflers as a pressure wave termination box doesn't make any sense to me. I thought the purpose was to tune the header + "extension" length just like open headers by having the large exhaust volume (muffler/wave term box) at the tuned length.

(Place the opening into the muffler chamber at the point that PipeMax tells you to; no?)


Adam

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