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Any downsides to anti reversion mufflers/devices?

General engine tech -- Drag Racing to Circle Track

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

Post by NewbVetteGuy »

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
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Re: Any downsides to anti reversion mufflers/devices?

Post by Carnut1 »

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
When done right the ar will mellow out the idle and make the tip in very snappy. To the point when people will tell you that there is no way that is the cam you run as it idles like a kitten. Just the opposite of the extra exhaust duration cams just for the sound. Thanks, Charlie
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Re: Any downsides to anti reversion mufflers/devices?

Post by Bill Chase »

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
Anyone willing to go through the process of following pipemax recommendations, ar device testing wants a fast car that is quiet. It is always interesting how those that aren't trying to make max power want a lumpy idle. safe to say most reading this want as much power as possible, with oem like noise, vibration,harshness, and as close to oe throttle tip in response as possible.lots of ways to get a lumpy idle without spending time, energy and money on an optimized exhaust system.
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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.
These guys have this, as well as various 4-5-6" tips with 3" inlets that have a nice taper if used as a can, not much welding would be required. But here is the converter shell... http://www.siliconeintakes.com/dsm-inte ... 0YQAvD_BwE
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Re: Any downsides to anti reversion mufflers/devices?

Post by F-BIRD'88 »

For the DIY'ers here you can read about how to form exhaust pipe reducer cones for the choke taper on the inlet pipe that will extend into the AR chamber..
https://www.hotrod.com/articles/0703sr- ... red-cones/
The exact amount of choke point taper, taper angle degree and length may need to be played with.

On a 2-½" in/out pipe AR device (street stuff) I'm thinking 7° taper ,2-¼" to 2.45" choke minor diameter.. Bigger stuff may want different geometry...
Having the high flow catalytic converter core in there may not actually be a bad thing.
If net car acceleration and driving is better and noise is reduced a bit, its all good. Combo AR Chamber/High flow Cat.
My purpose is to improve the performance of a Mid Length header VS s long tube header.. Your end game may be different.
Last edited by F-BIRD'88 on Fri Feb 26, 2021 3:03 pm, edited 1 time in total.
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Re: Any downsides to anti reversion mufflers/devices?

Post by Bill Chase »

These https://www.facebook.com/marketplace/it ... 194022798/are what I was thinking about when I mentioned tips. They can be bought cheap, are usually t304 stainless steel
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Re: Any downsides to anti reversion mufflers/devices?

Post by Bill Chase »

NewbVetteGuy wrote: Tue Feb 23, 2021 8:33 pm For what it's worth CrateInsider.com's advice on the DynaTech/Hendren / Crate Insider AR "mufflers" is: "the longer the primary is, the closer you want the muffler to the collector; shorter primaries like 12-14" before AR muffler."

They say on a 604 circle track crate they're worth 15-25 ft lbs between 2,500 and 4,500 RPM. (275/280 roller cam @ lash, 208/221 @ 0.050", .474"/510" on 112 LSA).

--I wish I felt like I had a good guess for why a shorter primary would would want the AR muffler at a longer distance from the collector...


Adam
What are they considering long or short primary lengths? Any more info you recall? I went to their site, looked at the video, most of it is a sales pitch, no real hard data or numbers suggested for their use.
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Re: Any downsides to anti reversion mufflers/devices?

Post by BadSS »

This is the place I bought all the pieces to make up the 36" long (4"x8") terminator box I used to replace the mid-muffler and the two bullet mufflers on my 2009 G8 GT.
https://www.coneeng.com/mufflers.html

I can't say how much the increase in performance was from just the terminator box since it replaced three "mufflers". However, combined with the additional tuning required after the installation, it made a significant improvement in right off-idle and overall throttle response.

When I ran a 3" collector with a 3" exhaust back in the late 80s, I had two 3" to 4"' cones welded to 3" of 4" pipe in the middle with about 3" of the 3" pipe inserted into what I was calling an AR collector.
Image

My experience was similar to the OP's. I was running a 256/260-106 solid roller in a 10.89:1 406 and only a 3,000 rpm converter - this was my daily driver at the time. I was experiencing a little bit of a lull a couple hundred RPM off the converter before going with this collector set up. The collector fixed that, resulting in around a 0.15-second reduction in ETs as well as made a very noticeable improvement in off idle and part throttle acceleration. Even if it had not "fixed" the lull, I would have been happy with the increased part throttle response.
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Re: Any downsides to anti reversion mufflers/devices?

Post by F-BIRD'88 »

Good report.. A .15 ET reduction is not bad at all.
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Re: Any downsides to anti reversion mufflers/devices?

Post by Mikej26 »

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
Here’s how the idle sounds

https://www.instagram.com/p/CHGKkyBlcyy ... 3ohr58q469
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Re: Any downsides to anti reversion mufflers/devices?

Post by Bill Chase »

BadSS wrote: Sat Feb 27, 2021 5:17 pm This is the place I bought all the pieces to make up the 36" long (4"x8") terminator box I used to replace the mid-muffler and the two bullet mufflers on my 2009 G8 GT.
https://www.coneeng.com/mufflers.html

I can't say how much the increase in performance was from just the terminator box since it replaced three "mufflers". However, combined with the additional tuning required after the installation, it made a significant improvement in right off-idle and overall throttle response.

When I ran a 3" collector with a 3" exhaust back in the late 80s, I had two 3" to 4"' cones welded to 3" of 4" pipe in the middle with about 3" of the 3" pipe inserted into what I was calling an AR collector.
Image

My experience was similar to the OP's. I was running a 256/260-106 solid roller in a 10.89:1 406 and only a 3,000 rpm converter - this was my daily driver at the time. I was experiencing a little bit of a lull a couple hundred RPM off the converter before going with this collector set up. The collector fixed that, resulting in around a 0.15-second reduction in ETs as well as made a very noticeable improvement in off idle and part throttle acceleration. Even if it had not "fixed" the lull, I would have been happy with the increased part throttle response.
Were they mounted directly to the collector, or at the end of the typical 18" collector extensions?
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Re: Any downsides to anti reversion mufflers/devices?

Post by BadSS »

I cut off 3-4" of the header's collector and had a collector rings welded to the header and front of the "AR Collector". It was may daily driver and I never ran it uncapped.
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Re: Any downsides to anti reversion mufflers/devices?

Post by Bill Chase »

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

Post by dfarr67 »

A little old- does this contribute?


https://ls1tech.com/forums/generation-i ... sting.html
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Re: Any downsides to anti reversion mufflers/devices?

Post by BOOT »

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
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