Any downsides to anti reversion mufflers/devices?

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

Post by RevTheory »

Mike, did it have any affect on your idle? I'm wondering if they're too far downstream for that :-k
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Re: Any downsides to anti reversion mufflers/devices?

Post by F-BIRD'88 »

I'm thinking round or oval shaped 3"-3½ - 4" or 3"x5" case with cone taper along its length. Mine will be 2½" in out pipe size but mine is for street stuff. (2½" dual exhaust) Thinking a non symetric position of the entry pipe may help. The entry pipe may have a slight cone shape. Mine may integrate the cat converter core inside also.
Wondering if the A/R device is just after a pipe curve, if using a offset case/ pipe form is better or.
Some of Fueling's stuff is non-symetric.
A round or oval shape is much stronger than a 4 sided square shape. I like the H pipe. I think you are on to something. (A/R devices + H pipe combo)
Mine could be 3" in off the header collector but has to be 2½" out.
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Re: Any downsides to anti reversion mufflers/devices?

Post by Mikej26 »

RevTheory wrote: Tue Dec 21, 2021 8:53 am Mike, did it have any affect on your idle? I'm wondering if they're too far downstream for that :-k
It did actually. Idle vacuum went up to 10” from 8”. Also have had to lean to carb out significantly. Especially the idle/transition circuit. Made it way richer per AFR meter, I’m assuming because of improved draw through the carb? Or less EGR dilution?
RevTheory
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Re: Any downsides to anti reversion mufflers/devices?

Post by RevTheory »

F-BIRD'88 wrote: Mon Dec 20, 2021 1:48 pm
RevTheory wrote: Mon Dec 20, 2021 8:55 am Well of course I can't find one for 2.5 inch collectors #-o
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.
Since you checked the patents, are they indeed a choke?
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Re: Any downsides to anti reversion mufflers/devices?

Post by F-BIRD'88 »

I call it a choke. If the inlet pipe is tapered.
How much taper that enhances the effect has to be found.
You can google search anti reversion AND patent. easily.
Feuling has some interesting stuff .
Looking at different designs and the effective elements of.... Want a device that is not over engineered nor too expensive to fab up. The Dynotech A/R muffler device may well be the practical answer to a simple practical device. K.I.S.S. rule applies.
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Re: Any downsides to anti reversion mufflers/devices?

Post by Bill Chase »

Mikej26 wrote: Tue Dec 21, 2021 1:32 am 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.
How does it run in the final configuration versus the first location you tried right after the collectors? Thinking placement could shift the curve a little bit, interested in hearing your results
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Re: Any downsides to anti reversion mufflers/devices?

Post by Mikej26 »

Bill Chase wrote: Thu Dec 30, 2021 8:05 am
Mikej26 wrote: Tue Dec 21, 2021 1:32 am 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.
How does it run in the final configuration versus the first location you tried right after the collectors? Thinking placement could shift the curve a little bit, interested in hearing your results
Seems to have further improved the off idle and bottom end of the curve. Most noticeable in regular driving conditions via better throttle response etc. seems like it broadened the torque curve overall.
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Re: Any downsides to anti reversion mufflers/devices?

Post by chevyfreak »

Been following this subject,
Would a bigger volume within the a-r device be good/or bad?

I did a pontiac 455 swap into my 63 c10. I have stepped shorty headers that works within the space i have, 3" collector then comes down to 2.5". Been thinking on taking a 3" pipe and push it over the 2.5 section then it makes a a-r device. Image attached. Its just the lenghts thats bother me. 6" long and then taper it down ? or use the 3" with a bend going towards the rear and then taper it down? . Maybe the extra volume can work as a pwtb, cant say, but have been toying with some ideas.

Chevyfreak.
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Re: Any downsides to anti reversion mufflers/devices?

Post by BLSTIC »

lc-gtr-1969 wrote: Wed Dec 08, 2021 9:02 pm Sorry for dragging up an old thread, I just thought I would comment my experience with a Dynatech torque booster/ anti reversion chamber...

I installed one yesterday on my 350hp inline 6 running a 252/260@50 cam and a big port cylinder head designed for high rpm.

No dyno data but I can definitely say part throttle torque has increased from 2500 onwards. When feathering the throttle around a bend the car feels much more responsive and pulls easier onto the cam. A definite improvement.

I have not noticed much change with full throttle hp. On a street or circuit car I would not hesitate to install these. I can see pulling out of a corner would be improved for circuit work. You could hold the taller gear where without the booster I would probably drop back another gear.

I did not really notice any real difference to sound.

Just thought I would share!
I noticed in the latest Street Machine an LC/LJ that ran an N/A 10 second pass with a street drivable six in it fitted with a Duggan/J-ZED head.

Was that you? And have you got any pics of the headers?
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Re: Any downsides to anti reversion mufflers/devices?

Post by lc-gtr-1969 »

Nah, thats not me, that is Trevor Owen from Owen Race Engines... Amazing little package and it makes a fair bit more than my 350 odd hp... Think it made about 320hp at the wheels... But yes, that runs the same head as I run, JZED.
Fumbling around in the shed...
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Re: Any downsides to anti reversion mufflers/devices?

Post by malibuguy79 »

I recently made a different rear muffler section on my daily just to try things

It has 2 anti-reversion chambers, one minor step before the muffler, and another major one right at the exhaust tip, with a sizeable step down in tubing, since my exhaust is a bit big for the power.

Part throttle response has definetely improved with no discernable loss on top end. I find myself rowing the gears more just to play around with that little torque boost on tip in.

Just confirms I really need to re-engineer my whole exhaust
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Re: Any downsides to anti reversion mufflers/devices?

Post by RevTheory »

What do you guys feel is an adequate pipe diameter for a single tail pipe at ~500 hp? I'm giving serious thought to coming off the 2.5 inch collectors at the same diameter for 18 or so inches, into a pair of 4 x 20 inch terminator boxes (a/r step into the boxes) connected together by a 3 inch crossover pipe, out at 3 inch into dual 3 inch mufflers, joined together a little further back with a 3 inch in x 3.5 inch out y, another a/r step up to a single, 4 inch tail pipe.

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

Post by BLSTIC »

My recent simulations have told me that a 4-1 that goes straight to 2.5 => x-pipe => 2.5 => mufflers was wrong for a 480hp 289. A 2.25 choke and 3" piping made a notable mid-range difference with no top-end cost. I did not do runs to verify which change had what effect though (I was simulating the difference between two existing systems at the time, not trying to optimize). The implication is that the 2.5" piping each side was borderline at that level for flow capacity and the 2.5" not-choke didn't have enough velocity/energy/inertia to prevent reversion in the mid-range. Your mileage may vary, I'm a noob with fancy tools at this point, not anyone with actual experience
malibuguy79
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Re: Any downsides to anti reversion mufflers/devices?

Post by malibuguy79 »

RevTheory wrote: Wed Apr 20, 2022 7:50 pm What do you guys feel is an adequate pipe diameter for a single tail pipe at ~500 hp? I'm giving serious thought to coming off the 2.5 inch collectors at the same diameter for 18 or so inches, into a pair of 4 x 20 inch terminator boxes (a/r step into the boxes) connected together by a 3 inch crossover pipe, out at 3 inch into dual 3 inch mufflers, joined together a little further back with a 3 inch in x 3.5 inch out y, another a/r step up to a single, 4 inch tail pipe.

Any thoughts?
I feel like overall you might be a tad big but it also end use can sway requirements too. Normally with turbo cars north of around 400gross HP I like to see at least 3.5" (ive seen personally and other people's dyno results support that decision).

However on a N/A street application you can go a touch smaller to keep velocity up to improve drivability.

I thought I had a pretty firm grasp of most things before joining this forum and my eyes really opened.

Basically you want as much velocity as possible without choking off power development. If you would of came to my shop Id probably would of set you up with 2.5" duals going into a 3 or 3.5" tailpipe depending on end use. I am sure someone smarter then me will correct this if I am wrong.
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