Any downsides to anti reversion mufflers/devices?

[skinny z]

I do not think these AR Chambers are quite the same as termination boxes, both may help minimise reversion for obvious reasons, but as you suggest, I am not sure the AR chambers have the volume or dramatic change in area that a termination box will have to induce the engine thinking it has open headers.

If I could fit a termination box I would run one but room is quite tight under there...

I'm of the same thinking.
As for packaging, try fitting that under a 3rd gen f-body. And a lowered one at that.
That said, I can forgo the chambers and easily run an open header for the full effect. Which is something I hope to experiment with this test and tune season. That would be via cutouts at the appropriate distance from the collector.

[emsvitil]

I don't see why you couldn't combine the AR with a termination box by extending the pipe a ways into the termination box............

[RevTheory]

I don't see why you couldn't combine the AR with a termination box by extending the pipe a ways into the termination box............

That's how I've done mine; I just tend to blow them up unless the engine is mild.

[SchmidtMotorWorks]

Does anyone know of any examples of highly developed performance engines that have these devices?

Motorcycles?
Exotic cars?

[F-BIRD'88]

Does anyone know of any examples of highly developed performance engines that have these devices?

Motorcycles?
Exotic cars?

These engines don't tune or run at a low enough rpm to benefit..
IMHO anti reversion chambers will work best at relative low rpm and relative restricted inlet applications.
eg: 2bbl dirt oval engines.
Anything where running better at part throttle matters.
Especially if cammed with a tight LSA cam.
Eg: oval track. Anything where a wider powerband with added low rpm torque is better (auto trans, limited #of gears, limited torque converter stall choice), and WOT carb capacity (cfm) is limited.
Typical cammed up street/strip engines.

[F-BIRD'88]

May be some benefit on *some* turbocharged applications.
A cammed Harley bike engine with 2 into 1 headers may benefit.
A low cost alternative to a proper custom merge style header collecter with spear and correct collector choke design. Gives some of the gains of that.

[F-BIRD'88]

May show some benefits on applications where the headers primary tube lengths are shorter than optimum.
EG: "mid length headers" Especially at part throttle.

[F-BIRD'88]

Resulting changes in the amount of recycled exhaust gas (passive EGR effect) by reduced exhaust reversion with a added anti reversion device will probabily need changes to reoptimize the overall ignition timing curve. A reduction in recycled exhaust gas "dilution" say at part throttle will tend to speed up fuel burn time. EGR effect tends to slow combustion burn speed.
A engine tune that makes use of passive EGR may become more knock sensitive at some driving modes.

[SchmidtMotorWorks]

Does anyone know of any examples of highly developed performance engines that have these devices?

Motorcycles?
Exotic cars?

These engines don't tune or run at a low enough rpm to benefit..
IMHO anti reversion chambers will work best at relative low rpm and relative restricted inlet applications.
eg: 2bbl dirt oval engines.
Anything where running better at part throttle matters.
Especially if cammed with a tight LSA cam.
Eg: oval track. Anything where a wider powerband with added low rpm torque is better (auto trans, limited #of gears, limited torque converter stall choice), and WOT carb capacity (cfm) is limited.
Typical cammed up street/strip engines.

Has the mechanism by which these work been determined or is this just speculation?

I am not aware of evidence that they actually change reversion.

[408swinger]

Does anyone know of any examples of highly developed performance engines that have these devices?

Motorcycles?
Exotic cars?

4-Stroke MX bikes

[SchmidtMotorWorks]

Does anyone know of any examples of highly developed performance engines that have these devices?

Motorcycles?
Exotic cars?

4-Stroke MX bikes

Can you post an example?

[408swinger]

Ktm and Husky 450s. Possibly others but I ride a 2-Stroke and don't keep up on all the new model 4-Strokes . Actually I spend more time researching old Maicos like my 490 Alpha 1.
I can tell you I see those power bulges on most 4-Strokes I see on the track or trail.

[2Quickrides]

FMF swears by them on the 4 strokes. Just the Megabomb header made noticeable difference in low and mid range on a Honda 250 4-stroke (that was already known for it's low and mid range unlike the new ones)

[lc-gtr-1969]

I don't see why you couldn't combine the AR with a termination box by extending the pipe a ways into the termination box............

If it doesn't fit... basically the reason I didn't do a termination box with the anti reversion...

[SchmidtMotorWorks]

Ktm and Husky 450s. Possibly others but I ride a 2-Stroke and don't keep up on all the new model 4-Strokes . Actually I spend more time researching old Maicos like my 490 Alpha 1.
I can tell you I see those power bulges on most 4-Strokes I see on the track or trail.

Brief search indicates that it is a resonance chamber, didn't find anything about anti reversion.
In fact if it is a resonator, chances are that it actually returns beneficial reversion like a 2-stroke pipe does.