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Explanation of Dual Plane Intake, please

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Ok, been a while, I dealt with storms, being out of town, etc, lol. And I haven't gotten my Jeep Dyno'ed yet, so no news on the carb front.

Anyhow, been reading up on intakes, ram-air, pulsations, firing orders, dual plane/single plane, etc.

I can't seem to figure out this dual plane. Single plane, yeah, open space like ours, easy. But dual plane? All the cut always I see are 8 cylinders which are a mess, to me.

Am I correct in my thinking that it could be as simple as this? With a 2 barrel carb and a stock intake? I know, not as simple, but maybe doable? Anyhow, Not sure, but is this the correct theory?

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If I understand the theory correctly, it would seem that our firing order is actually well laid out? Or am I totally off here?

Thanks!!! As usual!
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Discussion Starter · #5 ·
That intake looks a lot less efficient than the stock intake. Much smaller passageways.
Lol, that is a stock intake photo I ripped off of Google just to show my idea in a picture.

It does look tiny in the pic, though. In person, on an engine, it looks alot bigger than this pic.

Wow, there is a "guy joke" in there.... lol
 

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Discussion Starter · #7 ·
I think it has to do with less reversal of airflow, the best I can explain.
Yeah, using a Weber 38/38, I wonder if 1 38 side could feed 3 cylinders. I honestly don't know. But I think the firing order would keep it from reversing air flow in this type of setup. But I really am not sure.

This is the stuff I think about throughout the day, lol. Probably drives some on here nuts.
 

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Discussion Starter · #8 ·
Ah, that explains it.

Yes, less efficient than the 242 intake.

Really wish this friggin' forum still had the Jeep information clearly visible. :mad:
To be honest, as I learn more and more about Jeeps, there could be some reorganizing, IMHO of the site. The YJ guys and CJ guys are separated, but we have the same engines, so to speak, lol. Go figure!!
 

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Discussion Starter · #11 ·
Three side-drafts and weld your own intakes?
Reversion is probably a non-issue for practical hp gains in a jeep
Agreed, it probably is, lol. But come on, you know I like to tinker!! Supposedly Dual Planes are better for low end TQ?

And yeah, you read my mind, looking at the cost of intake manifolds ($250 Avg!!! :oops:) and the work that would probably need to he done, I am now getting closer to the path of, "Well, at this point.... I may have to learn to weld...." lol.

It would be a good thing to learn in my industry anyhow.
 

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Well you dragged me down a side track- here’s a good read. Now how accurate this thread is I cannot say- but there is some good info here.
I wouldn’t engineer something from it but a good read… oops- see post 14 below.
 

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Science ;)
 

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Discussion Starter · #17 ·
Just build a stroker already and quit chasing these 1hp rabbit holes.
I wouldn't disagree with you on that, lol. But I like learning these things.

It's how I've learned alot of my other hobbies. I always go a different route than what can be googled. Just how I am, it usually pays off, too, physically and mentally. Financially? Not usually, lol.
 

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Discussion Starter · #18 ·
Still reading, holy cow, there is some awesome stuff in there!! Those guys dive deep, lol. Talking about how the Speed of Sound vs slower A/F mixture speeds, how super chargers can slow the speed while also filling the cylinders, etc. When they talk about the speed, and how it can naturally "force" air into an area and make it harder to bounce back, from valve closing, I thought of when I was looking into Velocity Stacks. Supposedly, they help in this arena, because of the fact they allow more air in easier, they actually can help "stuff" air into an intake and keep the flow in 1 direction. Interesting take on it. Anyhow, thanks for sharing that, @MrCamo !!!

I find that kind of stuff interesting, especially the controlling of speed of the gasses to mobe performance down low or up high, in a sense.

As a side note: Considering that I've built Form 1 Suppressors before, it still amazes me that air and fuel can move at the speed of sound in an intake. You'd think it would be louder, lol. Some of the stuff I learned in that arena could probably overlap in this area. Physics Theory behind it, but it just hasn't clicked in for me yet.
 

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I would have to re read the entire thread before I jumped in to make sure that I am not off base but I will gamble my reputation on sounding smart vs sounding stupid.

A dual plane works better at lower RPMs because it divides the intake in half. At lower RPMS the engine is pumping less air and whatever cylinder is trying to draw air and create a vacuum, it has to create a vacuum in the entire intake manifold. That is a lot of volume to create a negative pressure in. So if you cut an intake into half essentially, it has a smaller volume or area that it is trying to bring into a negative pressure or vacuum.

When you get to a higher RPM, the rest of the cylinders can help the other 7 more (speaking in V8 terms) in the intake when it comes to achieving the negative pressure or vacuum
 
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Discussion Starter · #20 · (Edited)
I would have to re read the entire thread before I jumped in to make sure that I am not off base but I will gamble my reputation on sounding smart vs sounding stupid.

A dual plane works better at lower RPMs because it divides the intake in half. At lower RPMS the engine is pumping less air and whatever cylinder is trying to draw air and create a vacuum, it has to create a vacuum in the entire intake manifold. That is a lot of volume to create a negative pressure in. So if you cut an intake into half essentially, it has a smaller volume or area that it is trying to bring into a negative pressure or vacuum.

When you get to a higher RPM, the rest of the cylinders can help the other 7 more (speaking in V8 terms) in the intake when it comes to achieving the negative pressure or vacuum
Yeah, from what I've seen, you are spot on. What you describe is exactly what I've heard as well, hence my interest in them, low RPM torque. In fact, people say they even idle better/stronger. Again, to support what you say, basically better vac Signal, even while barely "working".

I had an impromptu drive to South Carolina for work, so guess what I've been You Tube bingeing on? Lol

Another theory is that it stops reverse "waves". I had read this, but didn't understand it fully until a guy with a V8 on YouTube actually changed the timing sequence and cam as well!! (ETA: I suppose crank, too, I only saw the manifold, but clearly a humungous undertaking, IMHO.) He built some sort of fancy race engines. But he said it was imperative to do this if you run a dual plane, otherwise the idea can be useless if just slapped on. Which I now kind of believe, another guy that does alot of things on YT had an Edelbrock single plane, simply broke it apart, and put a piece of sheet metal in there, and it decreased Dyno #'s like crazy. I suspect, because of what the other fellow said, you had intake valves fighting eachother for the same amount of air, bad firing sequence not timed.

So, if true, as I eluded to, we "seem" (who knows if it holds in reality, lol) to have the perfect intake, according to the 1 fellow's theory.

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Imagine the red is a wall, and the red arrows is that barrel ONLY feeding those 3 cylinders. When valve 1 is closing, bouncing air mix back into the manifold, valve 2 is opening. They are separated and so don't fight each other or jostle AF mixture back and forth, if that makes sense, like they would in a single plane. And by the time valve 3 is opening, it has all that air in that smaller manifold to itself- catching valve 1's rejected air. Some say that this rejected air gets bounced BACK into the same spot, so valve 1 would get it's own rejected air again? Anyhow, point is, separation makes sense, no matter who gets the bounced back air mix. Out firing order is perfect for this type of setup it seems. If I'm looking at it right.

What I am kind of lost on now, is what happens when valve 3 goes to open, and that air has been sitting in that manifold dead, with no movement? After valve 1 rejected it. I suspect this may be why they sometimes notch the top of the dual plenum dividers. To keep some sort of vacuum in there, keep movement up? Even if a little bit of vacuum from the other side, it's better than dead. I suppose you could say that air rams would have the same issue, and supposedly they don't. Maybe it all happens fast enough and I'm over thinking it. Interestingly enough, that rejected air bouncing back into itself? Is also a principal in the Air Ram design I found. I think it was called "natural super charge" or something. (ETA: The air that gets rejected goes back toward the carb/intake wall, and then bounces back toward the intake valve, but NOW with new air as well, hence the "Super Charge Effect, old rejected air mix pushing new air mix into the head- so people spent time tuning these, it needs to be timed well.) Overall, a dual plenum is sort of a shorty version of a ram air, just splitting one carb, instead of 2, and obviously much shorter runners.

This rabbit hole also lead me to the idea of the carb base on our intake being 1 barrel front and 1 barrel back, basically pivot our base 90°. It would be hard to do, I think, and would have to change linkage, but does make me wonder why they laid the barrel holes out the way they did. Was it intended that way by design of the manifold? Or just to match an existing carb design?

My Weber carb plate points the barrels inward, too speaking of carb base design. Almost like a taper spacer does. But the top of our plenum is pretty thick, destroying that design. So the air mix more so, gets pointed to 2 walls, lol. A redesign of the top would not be a bad thing, IMHO.

I wish I could buy 2 or 3 intakes. Hell, I may, lol.

1: make the dual plane I showed in first post maybe take out the heat plate underneath? To get some working room? That may be tough, though

2: get rid of the seperated barrels and make an open plenum, to include maybe even tapering them towards the head, not barrels shooting straight down into spikes, flow them, think reverse velocity stack idea- I actually talked to Shawn Watson (CJ side) about this idea as well

3: barrels set 90° from what they are now, instead of Left Barrel and Right Barrel, a Front Barrel and Rear Barrel- maybe to include the blending idea in #2. This would probably help flow as well, each barrel has to be sucked from behind a wall, lol.

Here is stock flow:
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Here is my 90° angle idea:
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It would be hard to do, I think. But interesting to test out, I think.
 
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