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Re: Any downsides to anti reversion mufflers/devices?

Posted: Wed Mar 03, 2021 6:52 pm
by BOOT
Bill Chase wrote: Tue Mar 02, 2021 4:43 pm I ordered a pair of the 3" in /3". Out. Since they were all Dynatech had in stainless. It will be a little while before I install them. it is very much like the fueling device pics floating around, but the inside is a choke venturi shaped, roughly 2.5-2.7" vs fueling's straight through pipe. Just happens I have my caliper and snap gauges at the house, when they arrive I can get some detailed measurements. Should be here today or tomorrow.
My estimate was bout 2.75" be cool to see what you find they are.

Re: Any downsides to anti reversion mufflers/devices?

Posted: Wed Mar 03, 2021 6:54 pm
by BOOT
NewbVetteGuy wrote: Thu Feb 25, 2021 1:54 pm For those guys who just HAVE TO buy a cam to get that "classic" lumpy idle, small and fast-enough headers and AR mufflers seem like a good idea, so I have to ask: Do these AR devices reduce the lumpy idle sound? (That could be a "downside" for some people.)

(Is the sound primary driven by OVERLAP or REVERSION itself?)


Adam
Came across this vid when researching them not long ago https://www.youtube.com/watch?v=BPHs2KGHQFY

Re: Any downsides to anti reversion mufflers/devices?

Posted: Wed Mar 03, 2021 11:15 pm
by Mikej26
Bill Chase wrote: Tue Mar 02, 2021 4:43 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.
I ordered a pair of the 3" in /3". Out. Since they were all Dynatech had in stainless. It will be a little while before I install them. it is very much like the fueling device pics floating around, but the inside is a choke venturi shaped, roughly 2.5-2.7" vs fueling's straight through pipe. Just happens I have my caliper and snap gauges at the house, when they arrive I can get some detailed measurements. Should be here today or tomorrow.

I would be willing to ship to someone if they wanted to flow them.

Those are the same ones I have on my car. They definitely taper internally. This was a concern for me originally because I have a merge collector on my headers and I was uncertain whether installing these would be redundant or counterproductive. The car seemed to like them though.

Re: Any downsides to anti reversion mufflers/devices?

Posted: Thu Mar 04, 2021 1:50 pm
by BradH
I'm considering adding a set right after my x-pipe on my full 3" exhaust to the rear bumper. However, I don't like that the Dynatech 3" models neck down as has been described above and believe the 3" inlet to 3.5" outlet version w/ a 3.5" to 3.0" reducer would be my choice, as that model is still a 3" ID.
.

3.0" inlet / 3.5" outlet model
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Screen Shot 2021-01-03 at 9.52.08 AM.png
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View into 3.0" ID inlet (no neck-down
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Screen Shot 2021-01-03 at 9.57.20 AM.png
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Reducer to bring it back to 3.0" for the rest of the system
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3.0 OD x 3.5 ID_2.png
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I did consider the idea of putting them right after my collector flange, but don't think there's enough room to fit 'em in before the x-pipe entry pipes change direction.

Re: Any downsides to anti reversion mufflers/devices?

Posted: Thu Mar 04, 2021 6:43 pm
by F-BIRD'88
I believe that the geometry of the choke on the entry pipe may be a critical tuning element. Various sizes need to be tried to get it dialed in to your specific engine.
One engine may want more of a choke reduction than another to get the optimun anti-reversion action VS overall raw flow through.

Re: Any downsides to anti reversion mufflers/devices?

Posted: Fri Mar 05, 2021 4:51 am
by Bill Chase
BOOT wrote: Wed Mar 03, 2021 6:51 pm
Bill Chase wrote: Tue Mar 02, 2021 4:43 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.
I ordered a pair of the 3" in /3". Out. Since they were all Dynatech had in stainless. It will be a little while before I install them. it is very much like the fueling device pics floating around, but the inside is a choke venturi shaped, roughly 2.5-2.7" vs fueling's straight through pipe. Just happens I have my caliper and snap gauges at the house, when they arrive I can get some detailed measurements. Should be here today or tomorrow.

I would be willing to ship to someone if they wanted to flow them.
My estimate was bout 2.75" be cool to see what you find
It's 2.53" at the smallest point. Looks like a 3" long 15° taper from the inlet. The rest of the specs are as advertised. I was pleasantly surprised by the consistency from part to part. Nice piece, they are for 400-500 hp engines. They do have larger pieces available from profab that have a 3" inlet, and 3.5" outlet and are made of stainless. Available at crate insider made by profab for the 525 ls crate engines. They are supposed to be more inline for a 500-600 hp engine.

Given it's design now that I have it I really doubt the choke will hurt high rpm power much, if at all. Especially so close to the primaries where gas is hot and velocity is up. Should work out well for my little street car deal.

Re: Any downsides to anti reversion mufflers/devices?

Posted: Fri Mar 05, 2021 3:09 pm
by BOOT
Bill Chase wrote: Fri Mar 05, 2021 4:51 am It's 2.53" at the smallest point. Looks like a 3" long 15° taper from the inlet. The rest of the specs are as advertised. I was pleasantly surprised by the consistency from part to part. Nice piece, they are for 400-500 hp engines. They do have larger pieces available from profab that have a 3" inlet, and 3.5" outlet and are made of stainless. Available at crate insider made by profab for the 525 ls crate engines. They are supposed to be more inline for a 500-600 hp engine.

Given it's design now that I have it I really doubt the choke will hurt high rpm power much, if at all. Especially so close to the primaries where gas is hot and velocity is up. Should work out well for my little street car deal.
Thx for the info! I don't think it will, as you said it's close so velocity is up and exhaust flow is pulses. I still may try 2.75 for my one after the y-pipe since it'll have half the time between pulses.

Re: Any downsides to anti reversion mufflers/devices?

Posted: Fri Mar 19, 2021 12:03 pm
by dfarr67
Thinking about replacing a single 3in high flow cat with a Dynatech, emissions not required in this case- but what is a concern is noise. Will the dB stay almost the same of go up?

Re: Any downsides to anti reversion mufflers/devices?

Posted: Wed Apr 07, 2021 4:37 pm
by dfarr67
Giving this a bump,
Before I get serious again about tuning the fueling on the efi.....looking at these A/R devices. Which way to jump- buy an a/r muffler or use an existing bullet muffler in the system and install a fitted cone like this (example only):

https://www.amazon.ca/Flowmaster-R3530- ... 43&sr=8-26

Re: Any downsides to anti reversion mufflers/devices?

Posted: Wed Apr 07, 2021 5:15 pm
by F-BIRD'88
Consider using a hi flow cat converter case as a chamber..
Replace the inlet pipe on the cat with your reducer cpne pipe, protruding into the case as desired for effect.

You may even start a new fashion trend at the track.

Re: Any downsides to anti reversion mufflers/devices?

Posted: Wed Apr 07, 2021 6:06 pm
by RevTheory
Is a high-flow cat going to have the volume needed with all of that honeycomb business in there?

Re: Any downsides to anti reversion mufflers/devices?

Posted: Wed Apr 07, 2021 9:40 pm
by F-BIRD'88
RevTheory wrote: Wed Apr 07, 2021 6:06 pm Is a high-flow cat going to have the volume needed with all of that honeycomb business in there?
The core inside is mostly empty space.

Re: Any downsides to anti reversion mufflers/devices?

Posted: Thu Apr 08, 2021 2:49 pm
by Scavenger
In response to the catalytic converter chamber idea, I'm currently building a set of these to go right behind some 1.5" 180 degree headers for a 340 Mopar. I ended up using a couple cheap ebay megaphones, and flipping them around. https://www.ebay.com/itm/2-25-CHROME-RE ... 890.l49286

In my simple testing (with a shop air blow gun) a piece of 2.25 inch pipe inserted to the weld line of the two cone pieces from the short side, provided noticeable anti-reversion or diode like valving properties. Time will tell if they do their job as the headers are still under construction.

Re: Any downsides to anti reversion mufflers/devices?

Posted: Fri Apr 09, 2021 1:10 pm
by dfarr67
The example of the cat 'test pipe' I think earlier referenced- there was no 'chamber', it was a straight through pipe with a dummy cat shielding around it. I'm not willing to cut anything out of the system to install that particular piece- I would rather install a proper AR muffler for the effort involved. On the other hand- would this work be worth the effort?.....The currently installed racing bullet is 3.5in inlet/outlet with the usual perforated core and packing, weld the 3.5-3.0 in cone inside the inlet- small end downstream- would this be a waste of effort or worth a shot, no further tuning intended. I did notice the ball/socket flange is a terrible pinch point- looking to replace with a Marman type coupler at the same time.

Re: Any downsides to anti reversion mufflers/devices?

Posted: Fri Apr 09, 2021 6:17 pm
by F-BIRD'88
Trouble is the location where you want the anti-reversion chamber to be and the location you want the muffler at is 2 different things.. But you can try it..