Don Terrill’s Speed-Talk

I am curious if these Anti-Reversion chambers will help a Mid-Length header to restore some of the low/mid range torque loss VS a long tube header.. Have a situation where a long tube header will be a pain and a off the shelf Mid length header fits and makes life much easier.
need a 2.50" in 2.50" out version. 460 -520 horsepower output.

Engine makes great torque with long tubes. Would like to keep (most of) that thrua Mid Length header.
-Hedman #68600-

(the long tube header baseline is not a optimized header
at all . Off the shelf street stuff)

If the Anti- Reversion chambers reduce exhaust reversion and thus reduce exhaust gas dilution in the combustion chamber the reduction in residual exhaust gas remix should speed up combustion speed. Spark timing adjustment may be nessessary to optimize with now resulting LESS EGR effect.
If your engine seemed to be hungry for more spark advance than others similar, the anti reversion chambers may correct this. A minor carb jetting tweek msy be called for also.
Exhaust gas doesn't burn.. Less exhaust gas dilution allows for more air/fuel to combust.

Bill Chase wrote: ↑Fri Feb 19, 2021 5:28 am

Carnut1 wrote: ↑Wed Jul 03, 2019 12:00 pm MIke, I have had similar results with a.r. . I couldn't find any down side. Thanks, Charlie

Have you used them with a straight collector vs a merge collector? And where in the system did you place them? Full street exhaust, or just headers with extensions

I extended tge 3" collector and welded custom flanges to connect the full 3.5" exhaust with an H pipe. Early 90's

digger wrote: ↑Wed Jul 03, 2019 6:22 am they could potentially alter the pressure waves at certain rpms which may have negative consequences

Digger,
Are you able to model these shapes in EngMod4T?
When I try to visualize what happens with an AR device regarding pressure wave vs particle flow. I can see that particle flow is effected by the shape. Pressure? That is less than clear to me. It may be delayed (spread over time), but I also think it possible the shape may have no effect on the progression of pressure waves within a tube system.
Can you educate me?

I tested a pair of anti-reversion devices in the collectors of a 424 CID SB2.2 dirt late model engine and they filled a 90 lb ft "hole" in the torque curve just under 3K RPM.

There were slight low single digit losses here & there in the curve (4000-8000 RPM sweeps @ 300 RPM/sec), but nothing that would offset the big TQ gain

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

digger wrote: ↑Wed Jul 03, 2019 6:22 am they could potentially alter the pressure waves at certain rpms which may have negative consequences

Or possibly improve the pressure wave tuning no?

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

This looks like a job for Larry Meaux and PipeMax.

skinny z wrote: ↑Tue Feb 23, 2021 9:28 pm

digger wrote: ↑Wed Jul 03, 2019 6:22 am they could potentially alter the pressure waves at certain rpms which may have negative consequences

Or possibly improve the pressure wave tuning no?

yes, IMO normally it helps somewhere but is worse somewhere else as well.

pcnsd wrote: ↑Fri Feb 19, 2021 10:39 pm

digger wrote: ↑Wed Jul 03, 2019 6:22 am they could potentially alter the pressure waves at certain rpms which may have negative consequences

Digger,
Are you able to model these shapes in EngMod4T?
When I try to visualize what happens with an AR device regarding pressure wave vs particle flow. I can see that particle flow is effected by the shape. Pressure? That is less than clear to me. It may be delayed (spread over time), but I also think it possible the shape may have no effect on the progression of pressure waves within a tube system.
Can you educate me?

i have not had a chance to look at this. in theory yes. as there is a "collector style" intended for anti reversion devices when i was looking at the user manual but id need to ask Vannik as there was something i was unsure of.

I'm curious as to whether or not there's enough volume in that little chamber that's mostly inner tube to actually cause pressure waves to reflect.

These look like the 'bombs' they have been installing in Motocross exhaust systems for years now. I wondered if/when they would make the transition.

Is that what is inside one of those? I always figured it was just an expansion chamber of sorts but it would make a lot of sense if they were mini versions of these.

n2omike wrote: ↑Wed Feb 24, 2021 8:40 am These look like the 'bombs' they have been installing in Motocross exhaust systems for years now. I wondered if/when they would make the transition.

The "Powerbomb" pipe is basically a bulge with a perforated liner. Not so much anti-reversion. The Megabomb is a bit different with a larger chamber. It appears that Hytech has a patented anti-reversion chamber. Back last century, you could buy headers with AR cones in each pipe, at the header flange.