Any downsides to anti reversion mufflers/devices?

[RevTheory]

Since this isn't likely a wave-reflection device, wouldn't it be included into the total collector length if you were testing for length on the dyno? Once that was determined, you'd add some sort of termination box to separate that length from your exhaust system so dyno-optimized collector length that includes the a/r piece then terminator box and full exhaust system.

I'm thinking about maybe trying to use lengths of 4-inch pipe joined by a crossover for volume rather than trying to build another box that I'm pretty sure will self-destruct. With all the diesel guys doing 5-inch systems, you'd think the exhaust shop would have plenty of 4-inch stuff laying around. I guess an option would be to use the case of the a/r device as a starting point to bell out to maybe an 18-inch length of 4-inch and then taper down to your three inch system.

[skinny z]

I'm thinking about maybe trying to use lengths of 4-inch pipe joined by a crossover for volume...

Thought about that myself.
I've got a 2 x 2-1/2" to 3" y-pipe on the car now.

100_1848.JPG

Removing the aftermarket merge would in effect leave two collector extensions (in this case almost the ideal length as per PipeMax).
Replacing that merge with a length of 4" oval exhaust pipe like this:

Oval.jpg

There's just enough area for the two 2-1/2" pipes to fit.
If my math is correct, a 36" length of oval tubing would be enough of an "atmosphere" for 355 CID. The collectors extended in the tubing the requisite distance and a single 3" out the back. Also inserted into the oval pipe appropriately.
It's tight under my car but might be doable.

A little off the OP's topic but since the discussion of termination has come up, I thought I'd through this out there.

[F-BIRD'88]

What does CFD analysis suggest if the entry pipe is a slight (choke) cone shape and or is pushed into the chamber different amounts? Forward to reverse flow bias changes?

My thoughts exactly, the Hendren design is in fact a choke. Not just a pipe dumping into a slightly larger chamber.

How much choke taper (degrees of pipe taper) on the pipe going into the A/R chamber? If a slight choke works what does more pipe taper or a longer/shorter pipe taper change the A/R effect before it kills too much forward flow.

Do multiple A/R devices (2-3→) in series work any better than a single A/R device?

[Bill Chase]

What does CFD analysis suggest if the entry pipe is a slight (choke) cone shape and or is pushed into the chamber different amounts? Forward to reverse flow bias changes?

My thoughts exactly, the Hendren design is in fact a choke. Not just a pipe dumping into a slightly larger chamber.

How much choke taper (degrees of pipe taper) on the pipe going into the A/R chamber? If a slight choke works what does more pipe taper or a longer/shorter pipe taper change the A/R effect before it kills too much forward flow.

Do multiple A/R devices (2-3→) in series work any better than a single A/R device?

Currently out of town working. Can get detailed measurements for the 3" in 3" Dynatech piece I have, they are the authorized manufacturer Hendren racing was/is using. I'll be home Thursday night, can get you detailed measurements if it helps. Below is a link to the piece I have.

https://www.speedwaymotors.com/Dynatech ... 52671.html

[F-BIRD'88]

I searched all the patents.. Ahh!! ..They have stolen all my ideas! !!

[RevTheory]

Well of course I can't find one for 2.5 inch collectors

[F-BIRD'88]

Well of course I can't find one for 2.5 inch collectors

I'm going to build my own 2½" in/out (street stuff)
If it adds some low rpm torque or adds some torque at low mid rpm @ part throttle, its a win.
I'm going with a off the shelf mid length street header so looking to get back some of the low rpm torque traded VS a long tube header.
Interested in the details of various designs.
I have to put high perf Cats on this car so might as well try and modify the Cats to function as a simple A/R device without spending a million bucks.
Curious what happens +/- if when combined with a H- pipe. Should the "H" be fore or aft of the A/R devices.

Not expecting any down side.

[RevTheory]

Well of course I can't find one for 2.5 inch collectors

I'm going to build my own 2½" in/out (street stuff)
If it adds some low rpm torque or adds some torque at low mid rpm @ part throttle, its a win.
I'm going with a off the shelf mid length street header so looking to get back some of the low rpm torque traded VS a long tube header.
Interested in the details of various designs.
I have to put high perf Cats on this car so might as well try and modify the Cats to function as a simple A/R device without spending a million bucks.
Curious what happens +/- if when combined with a H- pipe. Should the "H" be fore or aft of the A/R devices.

Not expecting any down side.

I don't know what your timing is but I suspect it's sooner than mine so please let us know how it worked out. Now I would think (may God help us all, lol) that the a/r devise would act as a brick wall separating your collector length from everything else so all of your efforts to use volume as a means of wave reflection should come after it, shouldn't it?

This was the first time a vehicle accelerated harder after leaving the exhaust shop than it did going there with open headers. I don't think those boxes hung in there a month, though. I've got to figure out a better deal.

Boxfromleft (1).jpg

[F-BIRD'88]

See you're a guy who is not afraid to try something.
Using a oval shape cat converter case might be stronger.
Interesting.

[F-BIRD'88]

Might try making a folded box on a sheet metal brake instead of butt welding the 4 sides. Make (less) lap joints VS butt welded joints. Same on the end caps of the box.
Make a folded formed end cap that lap welds to the end.
Not as likely to crack the welds from heat cycles and pressure pulses..
I think you got something with the box design.

[F-BIRD'88]

There is a diy instructables tutorial on how to cut a round length of pipe and reweld it as a DIY cone shape pipe.
A lot stronger than a 4 sided welded cone box.
Less welds. I like what you did there.

[F-BIRD'88]

Just looking what you did and a bit of brainstorming allows me to solve a few problems on my design.
Adds strength, bolts together (to play with the "speed secrets" , inside) and uses all off the shelf exhaust parts and (header) gaskets. Makes it practical and tunable.

[RevTheory]

Let me know what you're thinking. Maybe we can put our heads together and come up with something that works, doesn't blow up and actually fits on something other than a lifted truck.

[Mikej26]

The AR devices I included in the pics are 3” inlet and outlet, but the internal portion tapers down to 2 1/2” and extends 1/2 to 2/3 of the way into the larger case/chamber. About where the tip of my thumb is in the side profile pic, maybe a bit further.

[Mikej26]

I settled on the final placement of mine on the inlet side of my X-pipe so that I had a decent amount of collector extension upstream of them. Very happy with the way it runs set up this way.