Merge collector and anti reversion muffler

[Mikej26]

So I bought a set of headers that have a proper merge collector on them. The exit of the collector is 3 inch. My question is would it be counterproductive to also run an anti reversion muffler on these?

The Dynatech AR mufflers are 3 inch and internally they taper into 2.5 in and exit at 3 inch.

Is having a choke point at the merge collector and then another choke point at the AR muffler and exhaust flow no no?

[cjperformance]

The setup you describe is not ideal unless the second reduction in diameter is at a tuned length.
Get onto pipemax, make sure the collector and pipes are correct, put the AR reduction at a tuned length and start from there. You may find that your combo and use likes a little shorter or longer than this so leave scope to adjust and trial.

[Mikej26]

Thanks. That’s what I was concerned about. I bought the AR mufflers to boost my previous set of cheap headers that had a basic 4 to 1 collector. Now with a merge collector involved to AR muffler seems somewhat redundant, especially if place right at the end of the header collector. I’ve never played with pipemax so I will have to look into that.

[Newold1]

In most performance headers the merge section (choke point as you call it) is usually at the merging end point of the individual cylinder pipes as they enter the collector, not at the end of the collector. A collelector system like that would ne a megaphone type collector not a merge collector.

[Mikej26]

In most performance headers the merge section (choke point as you call it) is usually at the merging end point of the individual cylinder pipes as they enter the collector, not at the end of the collector. A collelector system like that would ne a megaphone type collector not a merge collector.

These are as you described. The smallest diameter is at the point that the primaries tie in, then it opens up to 3” afterwards

[modok]

It is perfectly practical to put anti-reversion features throughout the system, but they do need to be proportioned correctly.
For instance, a slight reverse cone on the end of a megaphone is almost universally beneficial, but the key is how big.
Going UP to 3 inches then back down to 2.5, educated guess.... that is too extreme.

[exhausted]

Anti-reversion dams are neat little items that can be used to broaden a given power curve. A given header only "works" over a 2000 rpm or so band of a engines power curve. As most are tuned for most power at the power peak, the header is unable to protect the engine from "stuff" coming back into the engine too soon when rpm's fall below the desired or normal operating range. Best example are road racing, short track stuff or cars that don't or can't have enough gears to keep motor happy? Enter AR valves, and 421 headers, being the current best hope to help the bottom end of a power curve. I can not tell you how many customers dyno their engines starting at say 5500 rpm's but at the track the motors will see 4500 rpm quite often. Hello?

To answer the question I would need to know more of the variables here, but I wouldn't say its a "nono", there is a lot more to it than that. If your header is "proper" a 3" choke on a 4into1 header in my world is for about 700-900hp, so...we could start there.

An AR chamber is like a diode, it can and will reduce the "power" or "magnitude" of a pressure wave in one direction through it while not the other direction. It always works, the issue is does it help you with what you are doing? Flow is another issue. Some engine applications will not see a benefit incorporating AR devices as they do not suffer from low rpm reversion issues.

I would let out a little item here, you can "stack" AR devices on top of each other, like adding them together, bigger as they are added. In other words if a 2.75-3.00 Chamber is backed by a 3"- 4.00" chamber the effect is increased. It is not however the same function as a megaphone.That is something else.

[Mikej26]

I can’t figure out how to upload pics on here. If I try to as an attachment it says they’re too large. I will try to get some actual measurements of the smallest diameter of the collector just after where the 4 primary pipes tie in. The primaries are 1 3/4”. The final exit of the collector is 3”. Without measuring I’d say the smallest point of the collector upstream of the exit where the primaries merge in is around 2 1/2”. The anti reversion mufflers are Dynatech, but they look just like the Hendren type. 3” inlet and outlet, but the inlet side tapers to 2 1/2” internally where it inserts into the slightly large case. With all that said, if they are worth using on a 3” exhaust system with an x pipe, where in the system would be the best place to stick them?

[exhausted]

I can’t figure out how to upload pics on here. If I try to as an attachment it says they’re too large. I will try to get some actual measurements of the smallest diameter of the collector just after where the 4 primary pipes tie in. The primaries are 1 3/4”. The final exit of the collector is 3”. Without measuring I’d say the smallest point of the collector upstream of the exit where the primaries merge in is around 2 1/2”. The anti reversion mufflers are Dynatech, but they look just like the Hendren type. 3” inlet and outlet, but the inlet side tapers to 2 1/2” internally where it inserts into the slightly large case. With all that said, if they are worth using on a 3” exhaust system with an x pipe, where in the system would be the best place to stick them?

Depends on where there is room but I have done AR final collectors and a Hendren Piece after the xpipe or final Y. Don't use x pipes on race cars, single tube and AR usually just after the final Y. One pipe makes more torque.

[Mikej26]

Interesting.

This is a street/strip deal, more street than strip in reality.

My original thought was to place the AR mufflers either right at the collectors or on the inlet side of the x pipe. But now that you mention it, putting them on the outlet side of the x pipe makes some sense.

I’ve read some of your stuff on here and realize that you’re normally doing elite level racing exhaust systems so I really appreciate your insights on my basic set up.

The theory around well designed exhaust is a fascinating topic.

[ijames]

I can’t figure out how to upload pics on here. If I try to as an attachment it says they’re too large.

Get irfanview from www.irfanview.com or some other freeware image editor and reduce the resolution down to something like 640x480 or so and you can upload it as an attachment. If you really need a higher resolution picture you will have to upload it to a hosting site like dropbox or imgur, and post the link.

[Newold1]

Thanks Calvin for coming on here to share your knowledge and expertise to help some of us exhaust deficient users!!

[Mikej26]

Thanks for the dropbox idea. Hadn't even crossed my mind.

Scavenging spike inside collector:

https://www.dropbox.com/s/2jvcb432tk52b ... 7.jpg?dl=0

Collector:

https://www.dropbox.com/s/443dqypxdmysy ... 6.jpg?dl=0

Full header:

https://www.dropbox.com/s/snh9b4we0q3z3 ... 9.jpg?dl=0

[Mikej26]

AR mufflers

External:

https://www.dropbox.com/s/xsi61qy3da7d3 ... 1.jpg?dl=0

Intlet side:

https://www.dropbox.com/s/f84o2b8uau8fp ... 7.jpg?dl=0

Outlet side:

https://www.dropbox.com/s/byxlhcvs0c9hf ... 2.jpg?dl=0

[Mikej26]

Mufflers currently are borla proxs.

But also have a set of hooked aerochamber that have an internal venturi built into them which I'm undecided about installing