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Any downsides to anti reversion mufflers/devices?

General engine tech -- Drag Racing to Circle Track

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F-BIRD'88
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Re: Any downsides to anti reversion mufflers/devices?

Post by F-BIRD'88 »

These AR chambers appear to be mini versions of David Vizard's Exhaust collector Termination Box.
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Re: Any downsides to anti reversion mufflers/devices?

Post by RevTheory »

F-BIRD'88 wrote: Wed Feb 24, 2021 1:51 pm These AR chambers appear to be mini versions of David Vizard's Exhaust collector Termination Box.
Vizard's chambers incorporate a metric shit-tonne of volume for reflection and then the inlet sticks into the chamber an inch for anti-reversion. I wish I knew just how much volume was required because building large boxes sucks.
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Re: Any downsides to anti reversion mufflers/devices?

Post by F-BIRD'88 »

Or how much box volume you could shrink down and still get most of the effect.. Yet fit under your car.
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Re: Any downsides to anti reversion mufflers/devices?

Post by F-BIRD'88 »

Seems that a typical aftermarket high flow catalytic converter case may be usefull as a donor to do a home DIY AR chamber project. You can play with the input pipe inside (diameter, length, protrution, choke taper) and play with the case volume/length +/-
I suspect that these may functoon as a single stage, simplified , practical version of a Tesla Valve.
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Re: Any downsides to anti reversion mufflers/devices?

Post by SchmidtMotorWorks »

Has anyone measured flow in both directions to determine the difference in flow?

I did this once for an intake manifold device, intuitively it looked like it might be AR, the flow difference was insignificant.
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Re: Any downsides to anti reversion mufflers/devices?

Post by digger »

SchmidtMotorWorks wrote: Wed Feb 24, 2021 3:51 pm Has anyone measured flow in both directions to determine the difference in flow?

I did this once for an intake manifold device, intuitively it looked like it might be AR, the flow difference was insignificant.
I've done CFD on things like this and yes at steady state the difference is always much smaller than intuition tells you. Though i suspect anti reversion devices require a transient analysis to properly quantify the resistance of the flow to change direction over a brief period of time. I suspect the flow takes longer to reverse direction and achieve the steady state /stable flow patterns
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Re: Any downsides to anti reversion mufflers/devices?

Post by SchmidtMotorWorks »

Yeah, I suspect in transient that there could be surprises from a multi-cycle cumulative effect to it being diminished by a low velocity period where reverse flow is slow enough to get by the AR without much resistance.
Also, it might be that distance from the valve is critical or that being before or after a merge matters too.

So I am more interested in getting a good understanding of how it works than buying into test results.
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Re: Any downsides to anti reversion mufflers/devices?

Post by NewbVetteGuy »

SchmidtMotorWorks wrote: Wed Feb 24, 2021 3:51 pm Has anyone measured flow in both directions to determine the difference in flow?

I did this once for an intake manifold device, intuitively it looked like it might be AR, the flow difference was insignificant.
Have you ever done this for a D-port exhaust port to a normal round port header, out of curiosity?
-Always hear the statement that there's AR value in round header and D-port exhaust but I don't think I've seen it tested / validated even once before.


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Re: Any downsides to anti reversion mufflers/devices?

Post by digger »

NewbVetteGuy wrote: Wed Feb 24, 2021 5:26 pm
SchmidtMotorWorks wrote: Wed Feb 24, 2021 3:51 pm Has anyone measured flow in both directions to determine the difference in flow?

I did this once for an intake manifold device, intuitively it looked like it might be AR, the flow difference was insignificant.
Have you ever done this for a D-port exhaust port to a normal round port header, out of curiosity?
-Always hear the statement that there's AR value in round header and D-port exhaust but I don't think I've seen it tested / validated even once before.


Adam
whenever you have an area change you have a reflection, how does one decouple the reflected wave vs reverse flow to understand what is going on with a typical dyno test?
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Re: Any downsides to anti reversion mufflers/devices?

Post by skinny z »

RevTheory wrote: Wed Feb 24, 2021 2:10 pm I wish I knew just how much volume was required because building large boxes sucks.
Isn't that spec'd in one of DV'S books? Something along the lines of an empty muffler case per side of a typical V8.
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Re: Any downsides to anti reversion mufflers/devices?

Post by digger »

skinny z wrote: Wed Feb 24, 2021 6:27 pm
RevTheory wrote: Wed Feb 24, 2021 2:10 pm I wish I knew just how much volume was required because building large boxes sucks.
Isn't that spec'd in one of his books?
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Re: Any downsides to anti reversion mufflers/devices?

Post by RevTheory »

skinny z wrote: Wed Feb 24, 2021 6:27 pm
RevTheory wrote: Wed Feb 24, 2021 2:10 pm I wish I knew just how much volume was required because building large boxes sucks.
Isn't that spec'd in one of DV'S books? Something along the lines of an empty muffler case per side of a typical V8.
It is but I've also seen several guys saying that not nearly that much is needed. I can't remember where though nor have I been able to try it.
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Re: Any downsides to anti reversion mufflers/devices?

Post by n2omike »

digger wrote: Wed Feb 24, 2021 6:30 pm
skinny z wrote: Wed Feb 24, 2021 6:27 pm
RevTheory wrote: Wed Feb 24, 2021 2:10 pm I wish I knew just how much volume was required because building large boxes sucks.
Isn't that spec'd in one of his books?
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You ever see a muffler for a Model A Ford? Looks a lot like that top picture... and I believe they are also hollow inside like that.

Image

Image
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Re: Any downsides to anti reversion mufflers/devices?

Post by Bill Chase »

F-BIRD'88 wrote: Wed Feb 24, 2021 2:55 pm Seems that a typical aftermarket high flow catalytic converter case may be usefull as a donor to do a home DIY AR chamber project. You can play with the input pipe inside (diameter, length, protrution, choke taper) and play with the case volume/length +/-
I suspect that these may functoon as a single stage, simplified , practical version of a Tesla Valve.
Search google and ebay. You can buy the pieces, and even hollowed Out converter shells brand new. Nice thing is they are a decent grade of stainless. And for you california guys subject to roadside inspection they look like a functional converter. I'll search my browser history and post a link, ran across it when searching for flanges and bullet mufflers.
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Re: Any downsides to anti reversion mufflers/devices?

Post by skinny z »

digger wrote: Wed Feb 24, 2021 6:30 pm
skinny z wrote: Wed Feb 24, 2021 6:27 pm
RevTheory wrote: Wed Feb 24, 2021 2:10 pm I wish I knew just how much volume was required because building large boxes sucks.
Isn't that spec'd in one of his books?
Image
That's a bingo!
Of course this is all in an attempt to have open header mufflered performance.
Or you can just crack open the cutouts when you mean business. I'd indirectly asked Larry Meaux whether a cutout opened would still provide the necessary reflected pulse for scavenging even if the balance of the exhaust was still part of the air stream. My understanding is that it would. And considering the amount of real estate I have under my car, terminations boxes aren't likely. But cutouts are.
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