David Vizard's Pressure Wave Terminator Box?? and Anti Reversion?

[Logic]

Originally Posted by freebeard

This approaches the Tesla one-way valve. I was [conceptually] trying to get there with a ring of holes.

I would say that a bunch of small PWTBs, with half torus front ends and sharpened from the outside in 'pipes' and at slight angles to each other is the closest to a 3D Tesla Valve one could get Freebeard.

A difficult shape/s to fabricate, but one cant help wondering what effect such would have on exhaust flow and economy at low rpms.

The stock Tesla Valve for others reading this and wondering whatTH we're on about:
NB the acceleration of flow rate in the fast direction and ...er back-bounce from the open end.

https://www.youtube.com/watch?v=tcV1EYSUQME

[freebeard]

A difficult shape/s to fabricate, but one cant help wondering

OTOH:

https://www.forbes.com › sites › carolynschwaar › 2022 › 06 › 30 › 3d-printed-rockets-set-to-blast-off
3D-Printed Rockets Set To Blast Off - Forbes
30 Jun 2022The ability to 3D print our turbopump, including rotating Inconel shrouded impellers, thanks to Velo3D's zero-degree technology, makes it possible now at a lower cost and increased innovation...

[aerohead]

Originally Posted by Logic

I think the Anti Reversion Trap is about disrupting any backward flow aerodynamically.

Venting them into a specific sealed volume may make them more like PWTBs, but you WANT the pulses in the Branch to help pull the exhaust gasses out...
ie: If you moved them further down the pipes to get these pulses timed; you'd end up with a PWTB!

It's not an 'aerodynamic' phenomena. On David's typical Chevy small-block 350, it has to do with a MACH- 1.66 shockwave-induced, reflected-rarification-scavenging event, originating at the exhaust tip atmospheric interface. And the engine must have valve overlap in order for the effect to work.

[aerohead]

Originally Posted by Logic

For the PWTB: NO it is not.
Plz feel free to discuss that with David Vizard himself.
(You have heard of him haven't you..?)
He's active on YouTube and various forums IIRC.

He showed up in my library. He was with HOT ROD Magazine in 1984 and 1985.
Any interest in 'reversion' would be predicated upon first establishing that the engine's camshaft(s) incorporated valve overlap.
Without overlap, there is no reversion.
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Of great interest to me were his articles on hop-ups, rigorously calibrated and tested on a dyno.
With a set of anti-reversion headers, and at engine rpms which would be germane to 'eco-modding' , virtually 'ALL' aftermarket engine modifications 'hurt' fuel economy.
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Of all my materials on exhaust systems, the only mention of 'velocity' came from Ph.D., Mechanical Engineering, Edward F. Obert, University of Wisconsin.
And 'velocity' was only used within the context of 1,227-mph shockwaves passing the exhaust valve upon the initiation of blowdown.
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Any hypothesis regarding gas-dynamic 'velocity' becomes problematic, as the internal volume of an exhaust system is 'constant,' hence 'velocity' is also 'constant', with the exception of in the immediate vicinity of valves.
And this is a variable 'backpressure' issue.
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Valve overlap/ reversion is associated with 'hot cams', high-rpm power, often with compromised mid and low-range operation, and definitely loss of mpg, due to substandard BSFC, as demonstrated by David Vizard in his reporting.
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Since David IS very good about testing, it would have been instructive, had he presented a complete back-to-back performance comparison of a specific vehicle, with, and without his 'invention.'
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'ANY' internal change within the entire exhaust system can cause ultra-sonic wave reflections, in any direction, depending on the geometry of the flow mutilation.
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And whatever's done to the exhaust must be accompanied by a 'retuning' of not only the entire exhaust system, but also the induction.
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It appears that David simply created a single reversion cone for all the cylinders, as opposed to reversion cones at the flanges of each of the eight primary runners, as manufactured by Mr. Gasket's Blackhawk and Cyclone headers.

[aerohead]

The Tesla valve appears to function in a similar manner to Ford of Cologne's 'lamellar' grille, featured on the later model Mercury Capri.
We covered this a decade or so ago.

[aerohead]

Originally Posted by Blacktree

I'd like to offer a couple clarifications.

1) The pressure wave box doesn't cancel out the exhaust pulses. It terminates them. When the pressure pulse reaches the end of the pipe, it reverses and goes back up the pipe. The box allows you to have the benefits of tuned length header extensions, while also having a "real" exhaust system.

2) That volume calculation is specifically for an 8 cylinder engine. Hence the "8 times cylinder volume". The calculation also assumes a single pipe exhaust. Another way to look at it: the box needs to be at least the total volume of the cylinders feeding into it, preferably 1.5-2x.

1) can you be more specific in your use of the term 'pressure wave' ?
2) and does David imply that his invention performs regardless of whether the headers are 4-into-1, Tri-Y, or 180-degree ?
3) and everything downstream of his chamber is removed from the tuning equation?

[freebeard]

Ford of Cologne's 'lamellar' grille

DDG fails [citatioin needed]

[aerohead]

http://https://ecomodder.com/forum/s...ille-7838.html

Originally Posted by freebeard

DDG fails [citatioin needed]

It's in my aerodynamic photo albums. Not sure about the thread though.

[freebeard]

I figured out that there are more than the two albums listed in you Profile Page. I looked through three or four. Is this it?


Popular Mechanics mentions the A word

It was right next to this eye-opener.

Half-tonneau cover is in Ford's nursery.GM files for US Patent,1986.

[aerohead]

I'm going to lunch, but I'm about half way through David's video.
* An inconsistency in his logic is that, an open Mini Cooper header 'HAS' backpressure. It's not 'zero.' David simply has not accounted for it.
* The exhaust gas encounters backpressure at:
1) tulip valves
2) initial mandrel 90-degree bend
3) internal friction within the length of each four primary runners
4) interference where 180-degree out-of-phase primaries siamese
5) where siamese twins combine into collector
6) length of the collector
7) interface with the atmosphere
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8) the 'pressure wave termination boxes', while a 'void' are not at atmospheric pressure, as with the open header.
9) both 'pressure wave collection boxes' DO have bell-mouthed entries, which WOULD kill vena-contracta losses when entering the exit pipe to the rest of the exhaust system.
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10) In 1996, Sport Truck Magazine commented that straight-through glass-pack mufflers actually hurt performance do to internal turbulence caused by tube perforations and spirals, producing more backpressure than the muffler they replace.