Don Terrill’s Speed-Talk

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

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

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.

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

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

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.


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.

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.

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.